The U.S.-Japan Alliance

The U.S.-Japan alliance has long been an anchor of the U.S. security role in Asia and arguably a contributor to peace and prosperity in the region. Forged during the U.S. occupation of Japan after its defeat in World War II, the alliance provides a platform for U.S. military readiness in the Pacific. About 54,000 U.S. troops are stationed in Japan and have the exclusive use of 85 facilities. In exchange for the use of these bases, the United States guarantees Japan’s security.

Since the early 2000s, the United States and Japan have improved the operational capability of the alliance as a combined force, despite constraints. In addition to serving as a hub for forward-deployed U.S. forces, Japan now fields its own advanced military assets, many of which complement U.S. forces in missions like antisubmarine operations. The joint response to a 2011 tsunami and earthquake in Japan demonstrated the increased interoperability of the two militaries. Cooperation on ballistic missile defense and new attention to the cyber and space domains remains ongoing.

The U.S. Military in Japan:

54,000 troops with the exclusive use of 85 facilities


Japanese Prime Minister Shinzo Abe is a stalwart supporter of the alliance and has had notable success on his ambitious agenda to increase the capability and flexibility of Japan’s military. Abe’s dominance over Japanese politics since his election in late 2012 has created opportunities for more predictable alliance planning. Although constitutional, legal, fiscal, and political barriers hinder further development of defense cooperation, Japan is steadily expanding its capabilities and, subtly, its attitude toward the use of military force, which is constrained by the Japanese constitution.

Japan faces a complex security landscape in the region, with potentially significant implications for the alliance. North Korea’s increased ballistic missile and nuclear capabilities pose a direct threat to Japan. Both Japan and the United States view China’s growing power (especially military power) and territorial assertiveness in the East China Sea and elsewhere as a destabilizing force that diminishes U.S. influence and erodes longstanding norms in the region. Japan has pursued security cooperation with others, including Australia, India, and several Southeast Asian countries, both bilaterally and within the context of the U.S.-Japan alliance. Of particular concern to the United States is the tense Japan-South Korea relationship, which has prevented effective trilateral coordination. Without cooperation among its allies, the United States may find itself less able to respond to North Korean threats or to influence China’s behavior.

Limited resources could strain alliance capabilities as well as produce more contentious negotiations on cost-sharing. The Japanese government currently provides nearly $2 billion per year to offset the cost of stationing U.S. forces in Japan, in addition to purchasing millions of dollars of U.S. defense equipment annually. Furthermore, the alliance has faced new strains in recent years. U.S. President Donald J. Trump’s open skepticism of the value of U.S. alliances and his admiration of North Korean leader Kim Jong-un have exacerbated longstanding anxiety in Tokyo about the U.S. commitment to Japan’s security.

The U.S.-Japan Alliance

Updated June 13, 2019 (RL33740)
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The U.S.-Japan alliance has long been an anchor of the U.S. security role in Asia and arguably a contributor to peace and prosperity in the region. Forged during the U.S. occupation of Japan after its defeat in World War II, the alliance provides a platform for U.S. military readiness in the Pacific. About 54,000 U.S. troops are stationed in Japan and have the exclusive use of 85 facilities. In exchange for the use of these bases, the United States guarantees Japan's security.

Since the early 2000s, the United States and Japan have improved the operational capability of the alliance as a combined force, despite constraints. In addition to serving as a hub for forward-deployed U.S. forces, Japan now fields its own advanced military assets, many of which complement U.S. forces in missions like antisubmarine operations. The joint response to a 2011 tsunami and earthquake in Japan demonstrated the increased interoperability of the two militaries. Cooperation on ballistic missile defense and new attention to the cyber and space domains remains ongoing.

The U.S. Military in Japan:
54,000 troops with the exclusive use of 85 facilities

Japanese Prime Minister Shinzo Abe is a stalwart supporter of the alliance and has had notable success on his ambitious agenda to increase the capability and flexibility of Japan's military. Abe's dominance over Japanese politics since his election in late 2012 has created opportunities for more predictable alliance planning. Although constitutional, legal, fiscal, and political barriers hinder further development of defense cooperation, Japan is steadily expanding its capabilities and, subtly, its attitude toward the use of military force, which is constrained by the Japanese constitution.

Japan faces a complex security landscape in the region, with potentially significant implications for the alliance. North Korea's increased ballistic missile and nuclear capabilities pose a direct threat to Japan. Both Japan and the United States view China's growing power (especially military power) and territorial assertiveness in the East China Sea and elsewhere as a destabilizing force that diminishes U.S. influence and erodes longstanding norms in the region. Japan has pursued security cooperation with others, including Australia, India, and several Southeast Asian countries, both bilaterally and within the context of the U.S.-Japan alliance. Of particular concern to the United States is the tense Japan-South Korea relationship, which has prevented effective trilateral coordination. Without cooperation among its allies, the United States may find itself less able to respond to North Korean threats or to influence China's behavior.

Limited resources could strain alliance capabilities as well as produce more contentious negotiations on cost-sharing. The Japanese government currently provides nearly $2 billion per year to offset the cost of stationing U.S. forces in Japan, in addition to purchasing millions of dollars of U.S. defense equipment annually. Furthermore, the alliance has faced new strains in recent years. U.S. President Donald J. Trump's open skepticism of the value of U.S. alliances and his admiration of North Korean leader Kim Jong-un have exacerbated longstanding anxiety in Tokyo about the U.S. commitment to Japan's security.


The U.S.-Japan alliance,1 forged during the U.S. occupation of Japan after the latter's defeat in World War II, provides a platform for U.S. military readiness in Asia. Under the Treaty of Mutual Cooperation and Security, Japan grants the U.S. armed forces the use of land and facilities in Japan in exchange for U.S. military support for the defense of Japan, among other things. Approximately 54,000 U.S. troops—"our most capable and advanced forces," according to the U.S. Department of Defense—are stationed in Japan.2 The United States has the exclusive use of 85 facilities throughout the archipelago, constituting the largest U.S. forward logistics base in the Asia-Pacific region;3 the small southwest Japanese island of Okinawa hosts 33 of these facilities. The U.S.-Japan alliance was originally constructed as a fundamentally asymmetric arrangement—Japan hosts U.S. military bases in exchange for a one-sided security guarantee—but over the decades this partnership has shifted toward more equality as Japan's military capabilities and policies have evolved. (See Appendix for historical background.) Japan boasts its own sophisticated defense assets and the two militaries have improved their bilateral capabilities, though alliance forces continue to struggle with interoperability as a result of their separate command structures, a challenge born of Japan's unique legal constraints on the use of force. Japan has remained constrained in its ability to use military force based on its U.S.-drafted pacifist constitution, as well as Japanese popular resistance to developing a more "normal" military posture.

The U.S.-Japan alliance has endured several geopolitical transitions, at times flourishing and at other moments seeming adrift. Once a bulwark against communism in the Pacific, the U.S.-Japan alliance was forced to adjust after the Soviet Union collapsed and the organizing principle of the Cold War became obsolete. The shock of the terrorist attacks on the United States in September 2001 ushered in a period of rejuvenated military ties, raising expectations in the United States that Japan would move toward a more forward-leaning defense posture and shed the pacifist limitations that have at times frustrated U.S. defense officials. However, the partnership struggled to sustain itself politically in the late 2000s; a softening of U.S. policy toward North Korea by the George W. Bush Administration dismayed Tokyo, and the stalled implementation of a base relocation on Okinawa disappointed Washington. After the left-of-center Democratic Party of Japan (DPJ) defeated the conservative, long-time ruling Liberal Democratic Party (LDP) in 2009, Tokyo's new leaders hinted that they might seek a more Asia-centric policy and resisted fulfillment of a 1996 agreement to relocate U.S. Marine Corps Air Station (MCAS) Futenma in Okinawa.

A series of provocations by North Korea and increasingly assertive (and at times aggressive) maritime operations by China starting in 2010 highlighted shared concerns about the region and appeared to set the relationship back on course and contributed to the return of bipartisan Japanese consensus in support for the alliance by the time the LDP unseated the DPJ as Japan's party in power in 2012. Meanwhile, the LDP had coalesced around leaders, including Prime Minister Shinzo Abe, who supported a more vigorous alliance and accelerating the expansion of Japanese military doctrine and capabilities. In 2015, the United States and Japan revised their bilateral defense guidelines, which provide a framework for defense cooperation, a demonstration of the enduring strength of the alliance, and a vision for enhanced cooperation in the future. Overall, this trend toward deeper security policy alignment and more integrated military operations has continued into the administrations of U.S. President Donald J. Trump and Prime Minister Abe. Questions linger, however, about the Japanese public's appetite for further expansion of the alliance, as well as if future leaders will embrace the more forward-leaning security posture that Abe has promoted.

Congress and the U.S.-Japan Alliance

Congress has expressed considerable interest in the U.S.-Japan alliance for a range of reasons. Many Members of Congress have focused on security issues, particularly China's military modernization and accompanying growing presence and activities in areas surrounding Japan, leading to congressional resolutions and letters that largely support Japan's position in territorial disputes.4 Abe addressed a joint meeting of Congress in 2015, the first time a Japanese leader had done so, to a warm reception. The bipartisan U.S.-Japan Congressional Caucus has more than 100 members, according to its website.5

Congress also exercises oversight of defense funding in the region, and has in the past intervened when troop realignment initiatives in Okinawa appeared to stall. In the 112th Congress, a bipartisan group of Senators called the realignment plans "unworkable and unaffordable."6 Concern about the ballooning costs of the Guam construction and the uncertainty surrounding the realignment led Congress to reject the Administration's request for related military construction funding in the FY2012 National Defense Authorization Act (NDAA), P.L. 112-81. Section 2207 of the act prohibited funds authorized for appropriation, as well as amounts provided by the Japanese government, from being obligated to implement the planned realignment of Marine Corps forces from Okinawa to Guam until certain justifications and assessments were provided. The FY2013 NDAA (P.L. 112-239) also prohibited U.S. Department of Defense (DOD) spending (including expenditure of funds provided by the Japanese government) to implement the realignment on Guam, with certain exceptions. In the 113th Congress, the FY2014 NDAA (P.L. 113-66) took the same approach to the Marine Corps realignment: an overall freeze on DOD spending on Guam, but with exceptions that allowed some related construction to go forward.

In recent years, security concerns have dominated congressional attention to Japan, but trade issues and questions about the cost of the alliance have surfaced from some Members. For example, some Members from major auto producing states raise concerns over what they view as unfair trade practices by Japan, citing nontariff barriers such as onerous testing and certification procedures as the cause of weak U.S. export sales to the Japanese market.

Passage of the Asia Reassurance Initiative Act (ARIA, P.L. 115-409) in late 2018 conveyed broad bipartisan support for the alliance.7 At a time when some U.S. allies are questioning the credibility and durability of the U.S. commitment to its alliances and to remaining an Asian power, ARIA aims to reassure U.S. allies that Congress is committed to a long-term strategy in the Indo-Pacific. The act emphasizes the need to "expand security and defense cooperation with allies and partners" and to "sustain a strong military presence in the Indo-Pacific region." The act recognizes the value of the U.S.-Japan alliance in promoting peace and security in the region; calls on the executive branch to deepen trilateral security cooperation with South Korea and Japan; and expresses support for the quadrilateral security dialogue with India and Australia. Among other things, the legislation imposes new reporting requirements on the executive branch and authorizes $1.5 billion annually to support various security initiatives.

Figure 1. Map of Japan

Source: Map Resources. Adapted by CRS.

The U.S.-Japan Alliance and the Trump Administration

The election of Donald Trump in 2016 stoked fears that the expansion of the alliance could slow. As a candidate, Trump sharply questioned the value of U.S. alliances and criticized Japan specifically, saying it failed to compensate the United States for protection. In 2017, these fears were somewhat allayed when Abe and Trump appeared to develop close personal rapport and coordinated on responses to North Korean nuclear and missile tests, which proliferated throughout the year. In addition, Trump reaffirmed the central aspects of the alliance early in his Administration, including asserting that Article 5 of the U.S.-Japan Treaty of Mutual Cooperation and Security covered the Senkaku Islands, which are administered by Japan but also claimed by China and Taiwan.8 (Article 5 states that the allies "would act to meet the common danger" of an "armed attack against either Party in the territories under the administration of Japan."9) During his first visit to Japan in November 2017, Trump articulated a U.S. "vision for a free and open Indo-Pacific," which echoed Abe's own concept of a "Free and Open Indo-Pacific."10 For several months, Abe was presented (and presented himself) as one of Trump's closest friends among international leaders.11

In early 2018, when the Trump Administration abruptly adjusted course and pursued negotiations with North Korea, many in Tokyo grew concerned about the possible marginalization of Japan's interests. (See "North Korea" section below.) In addition to Korean peninsula dynamics, the return of trade frictions to the forefront of the U.S.-Japan relationship since 2017 have raised concerns that the alliance could face challenges in the years ahead.

Postwar Japan has been an active and generous participant in international institutions that establish global rules, and some Japanese citizens and alliance experts have conveyed fears that the United States could drift as a steward of the international liberal order.12 Tokyo has paid close attention to the Trump Administration's approach to European allies and to South Korea. Japanese leaders have been concerned that Trump's harsh criticism of NATO's value and of South Korea's financial contributions to the U.S.-South Korea alliance indicates a broader dismissal of both military alliances and rule-setting organizations. Initially reassured by the presence of some senior officials in the Trump Administration, Japanese officials were alarmed by the departures of National Security Advisor H.R. McMaster and Defense Secretary James Mattis.13 Foreign officials had viewed Mattis' presence as tempering more skeptical U.S. views of overseas alliances. Appearing to reflect these concerns, Mattis' resignation letter dwelled on the value of alliances:

My views on treating allies with respect and also being clear-eyed about both malign actors and strategic competitors are strongly held and informed by over four decades of immersion in these issues. We must do everything possible to advance an international order that is most conducive to our security, prosperity and values, and we are strengthened in this effort by the solidarity of our alliances…. Because you have the right to have a Secretary of Defense whose views are better aligned with yours on these and other subjects, I believe it is right for me to step down from my position.14

China Emerges as Central Focus of Alliance

Strategic cooperation between the United States and Japan has increasingly focused on China as it has emerged as a major regional military power after decades of armed forces modernization fueled by a booming economy and fast-expanding defense budget. Emboldened by its own economic growth and a perception of U.S. decline, Beijing has asserted itself more forcefully in diplomatic and military arenas. This has included direct challenges to Japan's territorial claims to and administration of the Senkaku Islands, a set of eight land features in the East China Sea contested between Japan, China (which calls them the Diaoyu), and Taiwan (which calls them the Diaoyutai), and Beijing's ambitious multicontinent infrastructure programs that stretch across Asia and into Africa and seek to tie those regions more firmly to China politically and economically.

In successive Administrations, the United States has appeared to put more emphasis on its Asia-Pacific strategy as China expands its power and influence. In the early 2010s, as U.S. forces started extracting from wars in the Middle East in 2011, Washington's attention turned more toward the Asia-Pacific region. The Obama Administration aimed to build trade and strategic connections to the Asia-Pacific through expanded diplomatic, security, and economic engagement with the region. Its "rebalance" policy included, among other initiatives, the proposed 12-country Trans-Pacific Partnership (TPP) free trade agreement. The Trump Administration withdrew from the TPP, but introduced its own approach to the region, branding it the "Free and Open Indo-Pacific." The "free and open Indo-Pacific" expanded the geographic boundaries of the region with overtures to India to engage to its east. The embrace of this Indo-Pacific construct was seen as affirmation of a vision that Abe had promoted for years, and helped fuel the sense of strategic alignment in the early days of the Trump Administration.15 Both the "rebalance" and the "free and open Indo-Pacific" were broadly understood as a reaction to China's rise.16 DOD's Indo-Pacific Strategy Report, issued in June 2019, states that the "primary concern for U.S. security" is "inter-state strategic competition," particularly from China.17 Confronting the implications of this rise appeared to emerge as the major strategic anchor to the U.S.-Japan alliance.

U.S. and Japanese security strategy and policy documents are closely aligned regarding the perceived challenge posed by China.18 The Trump Administration frames its strategy toward China in terms of "great power competition," with the 2017 U.S. National Security Strategy describing China (and Russia) as seeking to "change the international order in their favor" and "challenge American power, influence, and interests, attempting to erode American security and prosperity."19 A summary of the 2018 U.S. National Defense Strategy asserts that China "seeks Indo-Pacific regional hegemony in the near-term and displacement of the United States to achieve global preeminence in the future."20 Japan's December 2018 National Defense Program Guidelines acknowledges the United States' "strategic competition" framework, and asserts "China engages in unilateral, coercive attempts to alter the status quo based on its own assertions that are incompatible with the existing international order."21 In a clear reference to China, an April 2019 joint statement by the U.S. and Japanese defense and foreign policy ministers "acknowledged their shared concern that geopolitical competition and coercive attempts to undermine international rules, norms, and institutions present challenges to the Alliance and to the shared vision of a free and open Indo-Pacific."22

Abe's Imprint on the Alliance

Abe, on track to become the longest-serving prime minister in Japanese history if he remains in his position until his term ends in late 2021, has been a stalwart supporter of the alliance, presenting the relationship as the backbone of Japan's strategic outlook. Abe has shown a willingness to push for changes to Japan's security posture—at times with significant political risk—that U.S. officials have encouraged privately for decades. Repeated election victories for his LDP party since it returned to power in 2012, the lack of competitive challengers for leadership within his party, and the disarray of the opposition gave him the political space to advance his long-standing agenda of increasing the flexibility and capabilities of the Japan Self-Defense Forces (SDF, effectively, the Japanese military). Although some of Abe's far-reaching aims—including amending Article 9 of Japan's constitution, which renounces "the threat or use of force as a means of settling international disputes"—appear to be out of grasp in the near term, he has accelerated Japan's incremental pattern of adopting more muscular security practices over the past several years. (See "Evolution of Japanese Defense Policy" section below).23 When Abe steps down (his current term expires in 2021, though some observers think he could potentially change party rules to seek a fourth term), it is unclear if the consensus to expand Japan's military power will hold.

Specifically, the Abe Administration has adjusted Japan's interpretation of its constitution to allow for the exercise of the right of collective self-defense, passed a security legislation package that provides a legal framework for the new interpretation, modestly increased Japan's defense budget, relaxed Japan's restrictions on arms exports, established a National Security Council to facilitate decisionmaking on foreign policy, passed a "State Secrets" bill that allows for more intelligence-sharing with the United States, and committed political capital and resources to advance the U.S.-Japan agreement to relocate the controversial MCAS Futenma airbase in Okinawa. (See "Okinawa-Guam Realignment and the Futenma Base Controversy" section below.)

Implementing many of these initiatives would entail overcoming considerable obstacles, but the momentum has created new energy in the alliance, along with new risks. In April 2015, the allies agreed upon a revision of the bilateral defense guidelines, the first such update since 1997. (See "2015 Revision of the Guidelines for U.S.-Japan Defense Cooperation and Establishment of the Alliance Coordination Mechanism" section below). The agreement was a centerpiece of Prime Minister Abe's summit with President Obama that same month, after which Abe addressed a joint meeting of Congress, a first for a Japanese prime minister. The new guidelines deepen alliance cooperation in a way that more intricately intertwines U.S. and Japanese security, making it difficult to avoid involvement in each other's military engagements. For Japan, this means potentially signing on to U.S. military priorities elsewhere, which could incite public resistance to expanding the SDF's mission. For the United States, it could raise the risk of entrapment into an armed conflict with China—most logically in the Senkaku/Diaoyu dispute.24 (See "China" section below for more detail.)

Toward a More Equal Alliance Partnership

The asymmetric arrangement of the U.S.-Japan alliance has moved toward a more balanced, integrated, and coordinated security partnership in the 21st century. The SDF is now active in overseas missions, including efforts in the 2000s to support U.S.-led coalition operations in Afghanistan and the reconstruction of Iraq. Japanese military contributions to global operations like counterpiracy patrols relieve some of the burden on the U.S. military to manage diverse security challenges. Advances in SDF capabilities give Japan a potent deterrent force that complements the capabilities of U.S. forces, for example in antisubmarine warfare and ballistic missile defense.

U.S. and Japanese forces also have moved to colocate their command facilities in recent years, allowing coordination and communication to become more integrated. The United States and Japan have been steadily enhancing bilateral cooperation in many aspects of the alliance, such as ballistic missile defense, cybersecurity, and military use of space. As Japan sheds its restrictions on the use of military force (in particular the constraints on collective self-defense) and the two countries continue to implement the revised bilateral defense guidelines, the opportunities for the U.S. and Japanese militaries to operate as a combined force could grow.

While Tokyo continues to see the U.S. alliance as the foundation of its security, conservative forces in Japan appear more serious about developing more military self-reliance.25 Tokyo is considering acquiring capabilities that could potentially be offensive in nature, which, if pursued, would represent a major shift in the traditional alliance arrangement whereby the United States is in charge of offensive strikes and Japan focuses on defensive operations. (See "Japan's Pursuit of Offensive Capabilities" section below for further discussion.)

Challenges to a Deeper Alliance

Japan and the United States share similar perceptions of the Asia-Pacific security environment, particularly regarding the threats of North Korea's missile and nuclear weapons programs and some aspects of China's military modernization; the value of advancing defense exercises and exchanges with the Republic of Korea (South Korea, or ROK), Australia, and India; and the goal of developing stronger security partnerships with Southeast Asian countries, particularly the Philippines and Vietnam.

Despite broad strategic alignment, both the United States and Japan face constraints on their ability to enhance the alliance. Constitutional and legal constraints abound on the Japanese side. Japan places tighter restrictions on its use of military force than other U.S. allies, including South Korea, Canada, and NATO countries.26 Fiscal conditions put pressure on defense budgets in both countries. Hosting U.S. troops has put strains on Japanese communities, particularly in Okinawa. Despite Abe's drive to upgrade Japan's security capabilities, it remains unclear whether the Japanese public has the appetite to shift Japan's fundamental postwar military posture of maintaining a relatively small military footprint.

Constitutional and Legal Constraints

Despite the passage of new security legislation in September 2015, several legal factors restrict Japan's ability to cooperate more robustly with the United States. The most prominent and fundamental is Article 9 of the Japanese constitution, drafted by American officials during the postwar occupation, which outlaws war as a "sovereign right" of Japan and prohibits "the right of belligerency." It stipulates that "land, sea, and air forces, as well as other war potential, will never be maintained."27 However, Japan has interpreted the article to mean that it can maintain a military for self-defense purposes and, since 1992, has allowed the SDF to participate in noncombat roles overseas in a number of U.N. peacekeeping operations (PKO), including in the U.S.-led coalition in Iraq. The 2015 security legislation adjusts the SDF rules of engagement (ROE) to allow more proactive missions and expands the scope for the SDF to operate in theaters where there is ongoing conflict, but not on the front lines. It also allows it to participate in non-U.N. PKOs in a similar capacity.28 The direct participation of the SDF in combat operations is considered to be unconstitutional unless there is a threat to Japan's existence. The overseas dispatch of the SDF requires approval of Japan's parliament, the Diet.

For years, Abe has spoken of his desire to amend the security provisions of Japan's constitution. This could include revising Article 9. Although Abe and others seem to prefer to make broad changes to Article 9, such as revising it to allow Japan to fully exercise the right of collective self-defense per the U.N. Charter, Abe has taken cues from a cautious public and advocated instead for a more narrowly-defined revision to enshrine the constitutional legitimacy of the SDF.29 Even as national support for changing the constitution appears to have incrementally increased in recent years, the amendment process is onerous, requiring approval by first a two-thirds majority of both houses of the Diet and then by a simple majority of a national referendum.30 Despite Abe's political strength, his ability to push through an amendment, which has yet to be drafted, is limited during his remaining years in office (his term is scheduled to end in September 2021).

Fiscal Constraints

Both Japan and the United States face serious fiscal constraints in their ability to maintain or increase defense budgets. Funding for new, expensive alliance initiatives appears to be limited; increased investments in new dimensions of alliance cooperation may come with trade-offs in existing or planned defense capabilities. Yet, U.S. and Japanese leaders have made rhetorical commitments to allocating a greater share of resources to bolstering the alliance.31

Under the Abe administration, the Japanese defense budget has risen steadily, as seen in Figure 2. At the same time, the rates of increase have not been significant enough to carry the budget away from the Japanese post-war tradition (not legally-binding) of spending 1% of GDP on defense. In comparison, over about the last decade, China is estimated to have spent about 1.9 percent of its annual GDP on defense and South Korea about 2.6%.32 Given that the Chinese economy has rapidly expanded while the Japanese economy has remained stagnant, this has resulted in an expanding differential in spending in real terms. Further, with gross public debt at roughly 250% of GDP and rising costs of the social safety net due to an aging and shrinking population, some analysts believe that it will be politically impossible for Japan to significantly increase defense spending. The 2019 National Defense Program Guidelines, which aim to guide Japanese defense policy for the next decade, acknowledges the impact that the nation's "severe fiscal situation" will have on defense.33

While President Trump has called for a bigger military budget, he has also called for a reassessment of defense cost-sharing between the United States and its allies.34 Prior to the Trump Administration, the United States had been implementing cuts to planned programs in its defense budget, partly through the sequestration mechanism established in the 2011 Budget Control Act. In testimony to Congress in February 2018, then-Pacific Command Commander Admiral Harry Harris warned against continued cuts, saying "Fiscal uncertainty breeds a significant risk to USPACOM's strategic priorities." He asserted, "One of the principal problems that we face in the region is overcoming the perception that the United States is a declining power. A fully resourced defense budget leading into long-term budget stability will send a strong signal to our allies, partners, and all potential adversaries that the U.S. is fully committed to preserving a free and open order in the Indo-Pacific."35

Figure 2. Japanese Defense Budget

With comparison to GDP

Source: Defense budget data obtained from: Japanese Ministry of Defense, "Defense Programs and Budget of Japan Overview of FY2019 Budget Request," at; GDP data obtained from: The Japanese Cabinet Office, Economic and Social Research Institute, "National Accounts," at

Notes: Values provided are in unadjusted terms based on each given year. The value for FY2019 is based on the 2019 budget request. The figure includes two sets of values. The first is the defense budget expenditures including "Special Action Committee on Okinawa (SACO)-related expenses, U.S. Forces realignment-related expenses (the portion allocated for mitigating the impact on local communities), and expense for the introduction of new government aircraft," noted in trillions of Japanese yen on the left-side axis. The second is the defense budget expressed as a percentage of GDP, noted on the right-side axis. This value is calculated based on Japanese fiscal year GDP data in Japanese yen, which are only calculated through FY2017.

Public Sentiment: How Far Is Japan Willing to Go?

Japanese voters have given the LDP five consecutive victories in parliamentary elections, but polls indicate that the electorate's approval of Abe is based on his efforts to revive the Japanese economy, as well as an opposition party in disarray, and not on security-related issues. Since World War II ended, the Japanese public has gradually changed from its pacifist stance to being more accepting of a more forward-leaning defense posture.36 This adjustment, however, has been largely incremental rather than fundamental. Observers caution that there is still deep-seated reluctance among the public to shift away from the tenets of the "peace constitution." Even as Japan's defense establishment moves to become more "normal," in the sense of shedding limitations on military activities, it is unclear whether the Japanese people are comfortable with these developments.

Periodic proposals to amend Article 9 of the constitution have met with resistance from many quarters. The LDP's junior coalition partner Komeito, the support base of which is largely pacifist, has hesitated to embrace far-reaching reforms of Article 9.37 Public opinion in Japan is split over whether to revise the constitution in general, with 2018 polls indicating 41%-45% of Japanese adults support revision. Regarding Article 9 in particular, a 2019 poll indicated 45% of Japanese adults support revising Article 9.38 According to a Council on Foreign Relations analysis of long-term polling trends, public enthusiasm for constitutional revision tends to reflect the priorities of whichever party is in power, and "the Japanese people are in no hurry to revise their constitution."39

The passage of the aforementioned 2015 security reforms in September 2015 illustrated the challenges of adjusting Japan's security posture. The LDP's push to pass the legislation generated intense opposition, both in the Diet and among the general public. The campaign galvanized widespread protest: local assemblies passed resolutions and nearly 10,000 scholars and public intellectuals signed petitions opposing the legislation. Media outlets in Japan claimed that over 100,000 people protested outside the Diet buildings after the bills were introduced. Demonstrators criticized the laws as unconstitutional and claimed that they risked pulling Japan into U.S.-led wars overseas.

Even as the Japanese public has become more comfortable with some expansion of the country's defense posture, including dispatching troops abroad in limited missions, profound questions remain about how willing Japan is to accept military risk. As Council on Foreign Relations analyst Sheila Smith points out, "No member of the SDF has died abroad…Should Japan's military be found wanting in response to a dangerous situation abroad, or should the situation end up costing SDF lives, the Japanese will have to decide if they are ready to accept that."40

Regional Security Environment: Threats and Partners

Changes in the East Asian security landscape have shaped Japan's defense approach and apparatus, and informed U.S. and Japanese efforts to reshape the alliance for the 21st century. For the past two decades, North Korea's belligerent rhetoric and repeated ballistic missile and nuclear weapons tests have heightened the sense of threat in Japan. China's military advances and increasingly bold maritime activities also have exacerbated Japan's sense of vulnerability, particularly since tensions over the disputed Senkaku/Diaoyu islets began to escalate in 2010.

As its perceived threats have grown, Japan has developed defense partnerships in the region, sometimes working through the U.S.-Japan alliance, and other times independently. The strong ties and habits of cooperation between the American and Japanese defense establishments complement existing and emerging regional security partnerships. The April 2015 and April 2019 joint statements released by the U.S. Secretaries of State and Defense and their Japanese counterparts (the so-called 2+2 meeting) praised progress in developing trilateral and multilateral cooperation, specifically with Australia, the Republic of Korea, and Association of Southeast Asian Nations (ASEAN) countries.41 The United States and Japan have cooperated on security capacity-building in Southeast Asia, especially since maritime territorial disputes in the East and South China Seas began to intensify in the late 2000s. Some analysts see these bilateral and multilateral links among U.S. allies and partners as beneficial to U.S. security interests by both enhancing deterrence and perhaps lessening the sense of direct rivalry with China.42

The two main mechanisms for U.S.-Japan regional security cooperation are high-level trilateral dialogues and multilateral military exercises. There is no comprehensive multilateral institution for managing security problems in the Asia-Pacific, although forums such as the ASEAN Regional Forum, the ASEAN Defense Ministers Meeting Plus, and the East Asia Summit have shown potential in this regard. Training exercises that allow the militaries of Asia-Pacific nations to interact and cooperate are another means to improve trust and transparency. The United States and Japan have participated in multilateral exercises with Australia, India, Mongolia, the Philippines, Singapore, South Korea, Thailand, Vietnam, and several other countries in recent years, indicating the breadth of these activities.


Increasingly over the past decade, concerns about China's rise have animated the U.S.-Japan alliance. Despite normalizing bilateral relations in 1972 and the huge volume of two-way trade between them, China and Japan have long been wary of one another. Efforts to stabilize the relationship in recent years notwithstanding, as China's military, economic, and political power have increased relative to Japan's, rivalry between the two countries has become the defining characteristic of their bilateral relationship.

Since 2010, mutual suspicion has solidified into muted hostility over the set of uninhabited Senkaku/Diaoyutai islets, located between Taiwan and Okinawa in the East China Sea. Japanese security officials have been deeply concerned about Beijing's intentions and growing capabilities for years, but the Senkakus dispute appears to have convinced politicians and the broader public that Japan needs to adjust its defense posture to counter China.

The longstanding but largely quiet dispute suddenly came to the fore in 2010, when the Japan Coast Guard arrested and detained the captain of a Chinese fishing vessel after it collided with two Japan Coast Guard ships near the Senkakus. The incident resulted in a diplomatic standoff, with Beijing suspending high-level exchanges and restricting exports of rare earth elements to Japan.43 In August 2012, in a move that drew sharp objections from the Chinese government, the Japanese government purchased three of the eight land features from a private landowner in order to preempt their sale to the Tokyo Metropolitan government under the direction of its nationalist governor at the time, Shintaro Ishihara.44

Starting in fall 2012, China began regularly deploying maritime law enforcement vessels near the islets and stepped up what it called "routine" patrols to assert jurisdiction in what it called "China's territorial waters." Chinese military surveillance planes reportedly entered airspace that Japan considers its own, in what Japan's Defense Ministry called the first such incursion in 50 years. In 2013, near-daily encounters escalated: both countries scrambled fighter jets, Japan drafted plans to shoot down unmanned aerial vehicles (UAVs) that do not respond to warnings, and, according to the Japanese government, a Chinese navy ship locked its fire-control radar on a Japanese destroyer and helicopter on two separate occasions.45 Chinese aircraft activity in the area contributed to an eightfold increase in the number of scramble takeoffs by Japan Air Self-Defense Forces aircraft between Japan Fiscal Year (JFY) 2010 (96 scrambles) and calendar year 2016 (842 scrambles). The number of scrambles decreased to 602 in 2017 and 581 in 2018; there were 162 in the first quarter of 2019.46

In November 2013, China announced an air defense identification zone (ADIZ) in the East China Sea that includes airspace over the islets, a move that Japan and the United States condemned as a destabilizing step that alters the already delicate status-quo.47 Experts argued that the ADIZ represented a new attempt by China to pressure Japan over the dispute, and that the ADIZ—which overlaps with three other regional ADIZs—could lead to accidents or unintended clashes. Although Chinese air forces have conducted patrols in the ADIZ, public reporting does not suggest China regularly enforces the ADIZ against foreign military or civilian aircraft.48

Rising tensions between Japan and China have direct implications for the U.S.-Japan alliance. The intermingling of fishing vessels, military assets, and maritime law-enforcement patrols creates a crowded and potentially combustible situation. With limited crisis management tools, China and Japan are at risk of escalating into direct conflict, which in turn could involve the U.S. commitment to defend Japan. As the Senkaku dispute has resurfaced multiple times since 2010, the United States reasserted its position that it would not take a position on sovereignty but that the islets are subject to Article 5 of the U.S.-Japan security treaty, which stipulates that the United States is bound to protect "the territories under the administration of Japan" (emphasis added). Congress inserted in the FY2013 National Defense Authorization Act (P.L. 112-239) a resolution that would appear to bolster the U.S. commitment by stating that "the unilateral action of a third party will not affect the United States' acknowledgment of the administration of Japan over the Senkaku Islands." Then-President Obama used similar language when describing the U.S. alliance commitment in April 2014, saying "The policy of the United States is clear—the Senkaku Islands are administered by Japan and therefore fall within the scope of Article 5 of the U.S.-Japan Treaty of Mutual Cooperation and Security. And we oppose any unilateral attempts to undermine Japan's administration of these islands."49 China's military modernization, more assertive approach to its territorial claims, and increased military activities around the Senkaku Islands and other southwest Japanese islands have led Japan to bolster its defense posture in the East China Sea (see "Evolution of Japanese Defense Policy" section below.)50

Chinese policy documents, official statements, and commentators regularly criticize the U.S.-Japan alliance, saying it represents "Cold War thinking," "hegemonic ideology," and an intent to contain China's rise.51 Reportedly, U.S. diplomats and defense officials have warned Beijing that Pyongyang's repeated missile and nuclear tests provide ample justification for improving U.S. and allied ballistic missile defense (BMD) capabilities in the region. At the same time, defense planners in the United States and Japan are concerned about the quantitative and qualitative improvements in Chinese military assets and capabilities, particularly cruise and ballistic missiles. China already has the ability to severely degrade U.S. and Japanese combat strength through conventional missile attacks on facilities in Japan, and the Chinese military fields antiship ballistic missiles that may be capable of destroying an aircraft carrier at sea.52

Policymakers in China and Japan appear to be making concerted efforts to stabilize the bilateral relationship after the most recent peak in tensions in 2016. In 2017 the Abe government revised its initial opposition to China's Belt and Road Initiative, saying that under the proper conditions Japan would cooperate with China in providing infrastructure development.53 In May 2018, at the first bilateral defense ministers' meeting in three years, the two countries agreed to enhance military exchanges and established a military hotline for senior defense officials to avoid an unintended maritime clash. In October 2018, Chinese leader Xi Jinping met with Abe in Beijing, the first dedicated top leaders' summit between the two countries since 2011. Some observers posit that the mutual interest in improving relations may be driven by both countries' trade frictions with the United States and a more general sense of uncertainty about the durability of the U.S. presence in the region.54 It remains to be seen whether and how long this period of thawing ties will last, given that deep-seated historical distrust and regional rivalry are unlikely to dissipate.

North Korea

North Korea's provocations have prompted critical changes in alliance priorities, activities, and investments, particularly in the area of BMD, and have played a forceful role in driving Japan's security policy, usually pushing Japanese leaders to pursue, and the public to accept, a more forward-leaning defense posture. After the Cold War threat from the Soviet Union receded, many analysts questioned whether the pacifist-leaning Japanese public would support a sustained military alliance with the United States. The shared threat from North Korea—particularly acute to geographically proximate Japan—appeared to shore up the alliance in the late 1990s and into the next century. North Korea's 1998 test of its first multistage rocket over Japan consolidated support for BMD cooperation with the United States. In 2001, the Japan Coast Guard's sinking of a North Korean spy ship that had entered Japan's exclusive economic zone again publicly raised the specter of the threat from Pyongyang. Perhaps most importantly, the admission by Kim Jong-il in 2002 that North Korea had abducted several Japanese citizens in the 1970s and 1980s shocked the Japanese public and led to popular support for a hardline stance on North Korea. 55 This in turn helped give rise to hawkish political figures, including Abe when he served as Chief Cabinet Secretary to Prime Minister Junichiro Koizumi from 2005 to 2006. In 2003, Japan launched its first spy satellite in order to track North Korean threats without relying on other countries' intelligence collection.

From 2006 to 2017, North Korea's behavior—repeated missile launches, six tests of nuclear devices, and its sinking of a South Korean warship and artillery attack on South Korea's Yeonpyeong Island in 2010—spurred Japanese leaders to pursue more robust missile defense cooperation with the United States. Japanese territory is well within the range of North Korean Nodong ballistic missiles, which are potentially capable of delivering a nuclear warhead.56 Given that U.S. military bases in Japan would play an important supporting role in a conflict on the Korean peninsula, many experts expect that Japan would be a target of North Korean missile attacks in a major crisis situation. Pyongyang's provocations also drove Seoul, Tokyo, and Washington to closer defense cooperation, including combined military exercises and high-level trilateral dialogues.

Japan was a strong supporter of the 2016-2017 U.S.-led "maximum pressure" campaign that aimed to squeeze the Pyongyang regime through robust international sanctions. Abe also supported Trump's "all options on the table" approach, suggesting that Japan would support the use of military force against North Korea. As the crisis defused in 2018 and the Trump Administration pursued a diplomatic path, diplomatic strains emerged as the United States, South Korea, and Japan approached the situation differently. The cancellation of large-scale bilateral military exercises between the United States and South Korea led Japanese officials to signal concerns about U.S. military readiness.57

South Korea

A complicating factor for U.S. defense strategy and U.S.-Japan coordination vis-à-vis North Korea is the dissonance between Tokyo and Seoul that thwarts robust trilateral defense cooperation. Japan-South Korea relations were particularly poor from 2012 until 2015, and plummeted again in 2018. U.S. officials have for years expressed their frustration at Japan and South Korea's failure to forge a meaningful bilateral defense relationship, which has complicated trilateral coordination. As the United States has encouraged Japan to upgrade its defense capability, public sentiment in South Korea sees the moves as an indication that Japan is reverting to the militarism that victimized the Korean Peninsula in the first half of the 20th century.

South Korea, a fellow free-market democracy and U.S. treaty ally, faces nearly identical security challenges to Japan: the armed, hostile, and unpredictable North Korea and the uncertain intentions of China. Both Japan and South Korea have a shortage of energy and other natural resources and depend heavily on shipping lanes to fuel their economies. Both share a desire for strong international bodies that set trade standards and protect intellectual property rights. The countries normalized relations in 1965 and are among each other's top trade partners.

Yet sensitive historical and territorial issues stemming from Japan's 35-year annexation of the Korean Peninsula from 1910 to 1945 have dogged the relationship and derailed attempts to cooperate in the security realm. Japanese officials argue that South Koreans show insufficient appreciation for Japan's apologies and Japanese restraint from venerating Imperial-era symbols, while South Korean officials argue that Japanese politicians have not learned and accepted the lessons of Japan's troubled past and that their apologies lack sincerity. Some South Koreans are particularly suspicious of Abe because of his perceived efforts to "remilitarize" Japan, and his controversial embrace of elements of Japan's imperial past (for example, Abe until 2013 would make public visits to the Yasakuni Shrine, which honors Japan's war dead, including convicted Class-A war criminals, a move that angered many Chinese and South Koreans).58

This mutual antipathy and political sensitivity hinders Japan-South Korea defense cooperation. Although the two countries were able to ink a basic military information sharing agreement (a GSOMIA, or General Security of Military Information Agreement) in 2016, reports suggest the mechanism is rarely used.59 In the past, North Korean military provocations provided an area of trilateral unity. However, with Washington and Seoul pursuing negotiations with Pyongyang, Japan and South Korea hold different views of how to approach North Korea, removing one of the most consistent pillars of bilateral agreement. More broadly, any strains on the U.S.-South Korea alliance may produce undercurrents of anxiety for Japan: strategic dissonance between Washington and Seoul could leave Tokyo feeling regionally isolated and even more dependent on the United States in the face of security threats. Japan is likely to feel more reassured by the U.S. alliance if Washington is committed to Northeast Asia as a whole.


After the United States, Japan's closest security partner is Australia, and increasing trilateral cooperation has been a key focus of alliance modernization efforts. Over the past decade, Japan-Australia defense ties have become increasingly institutionalized and regular. Australia is Japan's top energy supplier, and a series of economic and security pacts have been signed under Abe, including a $40 billion gas project, Japan's biggest ever foreign investment.60 Tokyo and Canberra have concluded a GSOMIA in 2012; an agreement on the transfer of defense equipment and technology in 2014; and an updated acquisition and cross-servicing agreement in 2017. Despite these advancements, however, Canberra and Tokyo have struggled to conclude a visiting forces agreement to allow Australian and Japanese military forces to conduct activities (such as military exercises) temporarily in each other's territories over a variety of concerns, including Australia's unease about Japan's death penalty laws.61

Although Japan had some difficult World War II history with Australia, Abe himself has made efforts to overcome this potential obstacle to closer defense ties. In 2014, during the first address to the Australian parliament by a Japanese prime minister, Abe explicitly referenced "the evils and horrors of history" and expressed his "most sincere condolences towards the many souls who lost their lives."62 In 2018, Abe visited Darwin, the first time a Japanese leader visited the city since Imperial Japanese forces bombed it during World War II.

Notably, even as Australia's leadership has changed hands six times in the past decade, the nation has consistently supported an expanded regional security role for Japan, despite concerns that such firm support might irritate China. Over the years, the Australian and Japanese militaries have worked side by side in overseas deployments (Iraq), peacekeeping operations (Cambodia, Timor-Leste, and elsewhere), and humanitarian assistance/disaster relief (HA/DR) operations, including the use of Royal Australian Air Force (RAAF) aircraft to transport SDF troops and supplies after the March 2011 disasters in northeast Japan.

Tokyo's defense relationship with Canberra has continued to expand both bilaterally and trilaterally through each country's treaty alliance with the United States.63 The Trilateral Strategic Dialogue, inaugurated in 2006, provides a framework for the United States, Australia, and Japan to cooperate on security priorities. The arrangement serves multiple purposes: it allows the United States to build up regional security architecture that supports its regional strategy, it offers training and exercise opportunities for militaries with similar equipment, and, many analysts say, for Australia and Japan, it offers a degree of strategic flexibility to assuage fears that U.S. commitment to the region could wane.64 The three militaries have conducted military exercises together on a regular basis. For example, the RAAF and Japanese Air Self-Defense Force (ASDF) train together with the U.S. Air Force in the Cope North and Red Flag exercises.


Both the United States and Japan see India as a potentially critical security partner in the region. Japan's security relations with India have strengthened since 2013 with an emphasis on maritime security in the Indo-Pacific region. Abe and Indian Prime Minister Narendra Modi have forged close political ties, building on Abe's interest in developing a partnership with New Delhi during his first stint as prime minister in 2006-2007. In December 2015, Japan and India signed a GSOMIA and an agreement on defense technology transfer. Both agreements appear to be laying the groundwork for further defense industry integration and capacity for intelligence sharing between the two militaries. Japan became a permanent participant in the previously bilateral U.S.-India Malabar naval exercises in 2015.

For India, deepening engagement with Japan is a major aspect of New Delhi's broader "Act East" policy. Analysts point to the lack of historical baggage between the two countries, mutual respect for democratic institutions, and the shared cultural and religious ties in Buddhism as factors contributing to the relationship. Over the past decade, both India and Japan have chafed at China's growing assertiveness (both have long-standing territorial disputes with China) and leaders in the two countries have sought to increase their bilateral cooperation in apparent response.

Alliance engagement with India is on the rise. The annual U.S.-India Malabar naval exercise, ongoing since 1992, expanded to include Japan on an irregular basis in 2009, and permanently in 2015. The three countries established a trilateral dialogue in 2011, and in 2018 Trump, Abe, and Modi held the first trilateral leaders' meeting on the sidelines of the G20 leaders' summit.65 The three countries, along with Australia, comprise a quadrilateral grouping, known as "the quad," which held its first meeting in 2017. See "International Operations and Cooperation" section, below, for more on the quadrilateral mechanism.


Part of Abe's diplomatic push has been to reach out to Russia, which could potentially introduce friction into the U.S.-Japan alliance. Japan and the Soviet Union never signed a peace treaty following World War II due to a territorial dispute over four islands north of Hokkaido in the Kuril Chain. The islands are known in Japan as the Northern Territories and were seized by the Soviets in the waning days of the war. Abe in recent years has reenergized efforts to resolve the dispute, and may hope that Japan and Russia's shared wariness of China's rise could lead to coordinated efforts to counter Beijing's economic and military power. Particularly in the past several years, however, China and Russia have developed closer relations and cooperate in multiple areas. Tokyo's ambitious plans to revitalize relations with Moscow, including resolution of the disputed islands do not appear to have made significant progress.

In the course of negotiations over the islands in 2018 and 2019, Russia and Japan agreed to use a 1956 joint declaration between Japan and the Soviet Union that would hand over the two smallest islands to Japan after concluding a peace treaty.66 However, Moscow has insisted that there could be no U.S. military presence on the islands, which Russia continues to view as strategically significant due to their location between the Sea of Okhotsk and the North Pacific Ocean. If Tokyo agreed, this would be an exception to the U.S.-Japan security treaty, which grants basing rights to the United States with Tokyo's consent.67 This could introduce tension in the U.S.-Japan alliance, particularly if U.S. relations with Russia worsen.

Meanwhile, Japan's ASDF continues to scramble fighter jets regularly in response to Russian aircraft activity off the northern part of the Japanese archipelago. According to statistics provided by the Japan Ministry of Defense, in some years the ASDF scrambled fighters against Russian aircraft nearly as many times as it did against Chinese aircraft in the southwest area.68


The United States and Japan have interests in Taiwan remaining a stable democracy that is free from coercion by mainland China.69 Though the United States tends to be more vocal in its support for Taiwan, Japan-Taiwan ties are quietly expanding as well. Japan and Taiwan, which have not had official diplomatic relations since 1972, have in particular flirted with the idea of establishing closer security ties, but the relationship is hindered by Japan's reluctance to antagonize Beijing. A number of recent actions highlight Tokyo's interest in cultivating a more cordial relationship with Taipei. Strong trade relations and people-to-people exchanges undergird the relationship, but Japan's official "One China" policy constrains the development of more regularized coordination. In 2016, Abe sent an official congratulatory message to Tsai Ing-wen when she was elected Taiwan's president. In 2019, Japan has voiced support for Taiwan's participation in the Comprehensive and Progressive Agreement for Trans-Pacific Partnership and in international organizations, such as the World Health Assembly, where China has blocked Taiwan's participation since 2017.70 In recent years, both Tokyo and Taipei have changed the names of diplomatic organizations to more explicitly acknowledge Taiwan instead of "Chinese Taipei" as Beijing has preferred.

On the security side, President Tsai has pushed for expanded cooperation. In an interview with the Japanese newspaper Sankei Shimbun in March 2019, President Tsai said "It is vital that talks [between Japan and Taiwan] be raised to the level of security cooperation," since "Taiwan and Japan are confronted with the same threats in the East Asian region."71 Cooperation nevertheless remains limited. Japan and Taiwan have delicately introduced a maritime cooperation dialogue, signed an MOU on search and rescue operations, and completed an East China Sea fisheries agreement, which the United States publicly welcomed.72 However, as Abe has made efforts to stabilize relations with China, these initiatives have remained quiet and mostly undeveloped. Observers say that the SDF is unlikely to adjust its policy of sending only retired officers to visit Taiwan.73 Short of a major diplomatic break with China, Japan is likely to remain cautious about more aggressively pursuing relations with Taiwan, despite multiple shared concerns.

Southeast Asia

As the disputes over territory and administrative rights in the South China Sea became more volatile during the 2000s and 2010s, the United States and Japan have made efforts to increase their contributions to security and stability in Southeast Asia, including by consulting on and coordinating security assistance to and engagement with Southeast Asian partners. Building the security capacity of Southeast Asian countries, especially in the maritime domain, is an area of joint effort for the alliance. In recent years, Japan has donated dozens of used and new patrol boats to coast guards in the region, complementing similar U.S. efforts toward building partner capacity and capabilities, such as the Indo-Pacific Maritime Security Initiative (previously the Southeast Asia Maritime Security Initiative), foreign military financing, international military education and training, and the Asia Reassurance Initiative Act.74 Maritime domain awareness is a priority area for cooperation in the near term. The level of cooperation with individual Southeast Asian countries varies widely, but generally Japan and the United States have been most engaged with the Philippines, Singapore, and Vietnam. In February 2016, Japan signed an agreement with the Philippines that establishes procedures for Japan to sell new military hardware, transfer defense technology, donate used military equipment, and provide training to the Philippine armed forces.

HA/DR operations, in which the U.S. and Japanese militaries have extensive experience, are another area of emphasis in disaster-prone Southeast Asia. Japan and the United States were two of the four non-Southeast Asian countries whose armed forces provided disaster relief following the 2004 Indian Ocean tsunami. The U.S. military and the SDF each sent approximately 1,000 troops and dozens of vessels and aircraft to assist the Philippines' recovery from Typhoon Haiyan (Yolanda) in 2013.75

Europe and the Middle East

As part of its attempts to diversify its defense partnerships, Japan has reached out to the North Atlantic Treaty Organization (NATO). Although Japan has been engaging with NATO since the early 1990s, it committed to enhanced cooperation on issues like Afghanistan, cybersecurity, nonproliferation, and other issues in a 2013 joint political declaration.76 With an emphasis on maritime security, Japan participates in NATO's Interoperability Platform (the "standing format for NATO-partner cooperation on interoperability and related issues"),77 and provides financial support for efforts to stabilize Afghanistan and assorted other NATO capacity-building programs.78 Recently Japan has participated in exercises in the Baltic Sea with the Standing NATO Maritime Group One.79

Amid escalating tensions between the United States and Iran, in June 2019 Abe made a two-day trip to Iran—the first by a Japanese prime minister in 40 years—in part to offer to mediate between the two countries so as to avoid an "accidental conflict" that could potentially affect all crude oil exports from the Persian Gulf. Japan had been a significant buyer of Iranian oil, but has bought only small amounts since U.S. sanctions on the importation of Iranian oil went back into effect in November 2018. Some observers suggest Japan could be a mediator both sides could trust, but others are skeptical of Japan's ability to bring Washington and Tehran to the negotiating table.80

Burden-Sharing Issues

During the course of the 2016 U.S. presidential election campaign, Republican presidential candidate Donald Trump contended that Japan (like other U.S. allies) should pay more host-nation support or face a drawback of U.S. defense commitments. These comments spurred debate on the proper burden-sharing arrangement and costs and benefits of U.S. alliances.81 In response, Japanese officials have defended the system of host-nation support that has been negotiated and renegotiated over the years. Defenders of the current arrangement point to the strategic benefits as well as the cost saving of basing some of the most advanced capabilities of the U.S. military, including a forward-deployed aircraft carrier, in Japan.

Putting a value on the U.S. military presence in Japan and calculating how much Tokyo pays to defray the cost of hosting the U.S. military presence is difficult and depends heavily on how the costs and contributions are counted. Is the U.S. cost determined based strictly on activities that provide for the defense of Japan, in a narrow sense? Or should calculations take into account the benefits of having American bases in Japan that enable the United States to more quickly, easily, and cheaply project U.S. power in the Western Pacific?

Determining the percentage of overall U.S. costs that Japan pays is even more complicated. According to DOD's 2004 Statistical Compendium on Allied Contributions to the Common Defense (the last year for which the report was required by Congress), Japan provided 74.5% of the U.S. stationing cost.82 In January 2017, Japan's defense minister told Japanese parliamentarians that the Japanese portion of the total cost for U.S. forces stationed in Japan was over 86%.83 Other estimates from various media reports are in the 40%-50% range. Most analysts concur that there is no authoritative, widely shared view on an accurate figure that captures the percentage that Japan shoulders.

Host-Nation Support

One major component of the Japanese contribution is the Japanese government's payment of $1.7 billion-$2.1 billion per year (depending on the yen-to-dollar exchange rate) to offset the direct cost of stationing U.S. forces in Japan (see Figure 3). These contributions are provided both in-kind and in cash.84 In recent years, the United States has spent $1.9 billion-$2.5 billion per year on nonpersonnel costs on top of the Japanese contribution, according to the DOD Comptroller.85

Japanese host-nation support is composed of two funding sources: Special Measures Agreements (SMAs) and the Facilities Improvement Program (FIP). First negotiated between the two countries in 1987, the SMA is a bilateral agreement, generally covering five years, which has obligated Japan to pay a certain amount for utility and labor costs of U.S. bases and for relocating training exercises away from populated areas. Under the current SMA, covering 2016-2021, the United States and Japan agreed to keep Japan's host-nation support at roughly the same funding level as it had been paying in the past. Japan is contributing ¥189 billion ($1.72 billion86) per year under the SMA and at least ¥20.6 billion ($187 million) per year for the FIP. The amount of FIP funding is not strictly defined, other than the agreed minimum, and thus the Japanese government adjusts the total at its discretion. Tokyo also decides which projects receive FIP funding, taking into account, but not necessarily deferring to, U.S. priorities.

Additional Japanese Contributions

In addition to the above noted host-nation support, which offsets costs that the U.S. government would otherwise have to pay, Japan spends approximately ¥182 billion ($1.65 billion) annually on measures to subsidize or compensate base-hosting communities.87 Based on its obligations defined in the U.S.-Japan Mutual Security Treaty, Japan also pays the cost of relocating U.S. bases within Japan and rent to any landowners on which U.S. military facilities are located in Japan. For example, Japan is paying for the majority of the costs associated with three of the largest international military base construction projects since World War II: the Futenma Replacement Facility in Okinawa (Japan provides $12.1 billion), construction at the Marine Corps Air Station Iwakuni (Japan pays 94% of the $4.8 billion), and facilities in Guam to support the planned move of 4,800 marines from Okinawa (Japan pays $3.1 billion, about a third of the cost of construction).88 See "Okinawa-Guam Realignment and the Futenma Base Controversy" section below for more details.

Indirect Alliance Contributions

Japan provides a number of additional monetary contributions to the United States. For example, Japan procures over 90% of its defense acquisitions from U.S. companies. (See "U.S. Arms Sales to Japan" below.) Japan plays an active role in U.S. extended deterrence through its BMD capabilities. (See "Ballistic Missile Defense Cooperation" and "Extended Deterrence" below.) Supporters claim that extended deterrence provides protection not only to Japan, but also to the United States from afar.

Figure 3. Host-Nation Support for U.S. Forces in Japan

Source: Japanese Ministry of Defense,; Federal Reserve Bank of St. Louis, Federal Reserve Economic Data, "Japan / U.S. Foreign Exchange Rate, Japanese Yen to One U.S. Dollar, Annual, Not Seasonally Adjusted,"

Notes: This graph uses data for budgeted expenditures for host-nation support for USFJ, not contracts. The costs shown, expressed in unadjusted billions of Japanese yen (left-side axis), are those the Japanese government reports as ''Cost-sharing for the stationing of USFJ." Not all costs listed above are considered by the Japanese government to be part of the U.S.-Japan Special Measures Agreement (SMA), and not all SMA costs are listed above because some are categorized under other U.S.-Japan agreements. Training relocation expenditures began in 1996 and are less than JPY 1 billion per year, significantly smaller than other expense categories. The line "Total in USD" is calculated based on the average unadjusted exchange rate between JPY and USD for each given year show, expressed in billions of U.S. Dollars (right-side axis).

U.S.-Japan Alliance: Bilateral Agreements and Cooperation

The U.S.-Japan alliance is built on a foundation of bilateral agreements that define the scope and form of security cooperation. The 1960 Treaty of Mutual Cooperation and Security is the bedrock of the alliance, covering the basic rights and responsibilities of each party. Particularly significant are Article 4, which requires the parties to hold consultations "whenever the security of Japan or international peace and security in the Far East is threatened"; Article 5, which requires the parties to "act to meet the common danger" of an "armed attack against either Party in the territories under the administration of Japan"; and Article 6, which grants U.S. Armed Forces the use of "facilities and areas in Japan."89

The accompanying 1960 Status of Forces Agreement (SOFA) governs the treatment of U.S. defense personnel stationed in Japan. The Guidelines for U.S.-Japan Defense Cooperation, first codified in 1978 and then updated in 1997 and 2015, provide the policy guidance to direct alliance cooperation. The guidelines outline how the U.S. and Japanese militaries will interact in peacetime and in war as the basic parameters for defense cooperation based on a division of labor.

Guided by this policy framework of bilateral agreements, Tokyo and Washington chart the course for alliance cooperation with several regular and ad hoc meetings and dialogues. At the highest level, alliance goals and priorities are set during leadership summits between the U.S. President and Japanese Prime Minister. The cabinet-level Security Consultative Committee (SCC) is the alliance's primary decisionmaking forum. Composed of the U.S. Secretaries of Defense and State and their Japanese counterparts, and thus known as the "2+2", the SCC meets roughly annually or biennially and issues joint statements that reflect present alliance concerns and provide concrete guidance for the near term.90 Some SCC meetings have been more far-reaching, elaborating on alliance priorities and common strategic objectives. Other alliance management fora include a Security Subcommittee, a Subcommittee for Defense Cooperation, and an Alliance Management Meeting.

The U.S.-Japan dialogue on the roles, missions, and capabilities (RMC) of the two militaries provides more concrete directives deriving from the policy guidelines. Supporting these broader alliance management fora and executing the day-to-day activities of the alliance are several issue-specific working groups, as well as a large number of officials tasked with various alliance management responsibilities throughout the U.S. Department of State, DOD, U.S. National Security Council, Japanese Ministry of Foreign Affairs, Japanese Ministry of Defense, Japanese National Security Council, and both countries' embassies and armed forces.

Table 1. Military Forces in Japan

Figures are approximate

Japan Self-Defense Forces (SDF)

2019 defense budget: 5.29 trillion yen ($48.12 billion)

U.S. Forces Japan (USFJ)

Maritime Self-Defense Forces (MSDF)

45,350 sailors

49 principal surface combatants (including 6 Aegis BMD-equipped combatants and 4 helicopter carrier destroyers); 6 patrol and coastal combatants; 27 mine warfare and countermeasures ships; 11 amphibious ships; 21 logistics and support ships

20 submarines, 275 naval aviation aircraft

U.S. Navy

20,250 sailors

1 aircraft carrier, 3 cruisers, 8 Aegis BMD-equipped destroyers, 1 amphibious command ship, 4 mine countermeasures ships, 1 amphibious assault ship, 1 landing platform dock, 2 landing ship docks

4 fighter attack squadrons, 2 antisubmarine warfare squadrons, 2 electronic warfare squadrons, 1 AEW&C squadron, 2 helicopter antisubmarine warfare squadrons, 1 transport helicopter squadron

Air Self-Defense Forces (ASDF)

46,950 airmen

189 fighter aircraft; 148 ground attack fighter aircraft; 3 electronic warfare aircraft; 17 intelligence, surveillance, and reconnaissance (ISR) aircraft; 17 airborne early warning & control (AEW&C) aircraft, 26 search as rescue aircraft, 6 tanker aircraft, 59 transport aircraft, 50 search and rescue and heavy transport helicopters

24 PAC-3 BMD units

U.S. Air Force

12,500 airmen

1 fighter wing at Misawa AB with 22 F-16C/D fighters, 1 fighter wing at Kadena AB with 27 F-15C/D fighters, 14 F-22A fighters, 15 refueling tankers, 2 AEW&C aircraft, 10 combat search and rescue helicopters, 12 transport aircraft, 1 special ops group, 1 ISR squadron

Ground Self-Defense Forces (GSDF)

150,850 soldiers

1 armored division, 3 mechanized infantry divisions, 5 light infantry divisions, 1 airborne brigade, 1 air assault brigade, 1 helicopter brigade, 1 artillery brigade, 2 air defense brigades, 1 special ops unit

U.S. Army

2,700 soldiers

1 special forces group, 1 aviation battalion, 1 surface-to-air battalion

SDF Amphibious Assets

GSDF Amphibious Rapid Deployment Brigade

3 landing ships (LST), 20 landing craft

U.S. Marine Corps

18,800 marines

1 Marine division, 12 F/A-18D ground attack fighters, 12 F-35B ground attack fighters, 15 refueling tankers, 12 helicopters, 24 MV-22B tiltrotor helicopters


54,100 soldiers, 1,100 sailors, 800 airmen

U.S. Strategic Command

2 AN/TPY-2 X-band radars

Sources: The Military Balance 2019, (London, UK: International Institute for Strategic Studies, 2019); "Japan's Newest Aegis-equipped Cessel, Maya, Launched in Yokohama," Mainichi, July 31, 2018, at; Japan Ministry of Defense, Defense of Japan 2018, White Paper, August 2018, p. 324.

Notes: The totals for the USFJ column account for U.S. forces stationed in Japan. The U.S. military is capable of augmenting these forces with reinforcements from elsewhere in the region, and around the world. The exchange rate is calculated at 110 JPY to 1 USD.

a. Japan intends to convert Izumo-class helicopter carrier destroyers to aircraft carriers capable of launching F-35s.

Major Outcomes from SCC ("2+2") Meetings

Over the years, SCC meetings have provided high-level guidance for significant alliance changes and initiatives. For example, the 2002 SCC established a Defense Policy Review Initiative (see "Defense Policy Review Initiative" section below), aimed at reviewing the alliance structure and objectives and adapting to the post-September 11, 2001 security environment. Following on this initiative, SCC meetings in the period 2005-2007 provided high-level guidance for many significant changes in the alliance, including the realignment of U.S. forces in Japan. The 2012 SCC updated the Defense Policy Review Initiative's objectives, and the 2013 SCC meeting set the task of revising the Guidelines for U.S.-Japan Defense Cooperation for the first time since 1997; the guidelines were approved and released at the 2015 meeting (see next section).

The 2017 SCC occurred during a period of heightened tensions with North Korea. As a result, the joint statement emphasized the importance of bolstering alliance capabilities to address "a new phase" of the North Korean threat. For the first time, the SCC statement expressed concerns about the security environment in the South and East China Seas. In addition to reconfirming that the U.S.-Japan treaty covers the East China Sea's Senkaku Islands, the statement noted "the significance of continued engagement in the South China Sea, including through respective activities to support freedom of navigation, bilateral and multilateral training and exercises, and coordinated capacity building assistance."91 The statement also emphasized efforts to advance regional security cooperation with partners like Australia, India, South Korea, and Southeast Asian countries, and Japan's intention to "expand its role in the alliance," particularly in the areas of "intelligence, surveillance, and reconnaissance (ISR), training and exercises, research and development, capacity building, and joint/shared use of facilities."92

Notable themes from the most recent SCC meeting, held in April 2019, include the prioritization of "new domains" of space, cyberspace, and the electromagnetic spectrum, and the necessity of an increasingly "networked structure of alliances and partnerships" in the Indo-Pacific. Most notably with regard to the first theme, officials publicly stated for the first time that "a cyber attack could, in certain circumstances, constitute an armed attack for the purposes of Article 5 of the U.S.-Japan Security Treaty."93 The U.S. State Department's fact sheet for the meeting emphasized "the integral role of space in full spectrum cross-domain operations," and noted that the participants prioritized cooperation on space situational awareness and "leveraging emerging, innovative space concepts."94 Regarding networked regional partnerships, the ministers built on themes from the 2017 SCC on the importance of cooperating and building capacity with regional partners through trilateral, quadrilateral, and other frameworks.95

Regarding the security environment, although the achievement of "final, fully verified denuclearization" was "at the top of the list" of alliance priorities according to U.S. Secretary of State Pompeo, China's challenge to regional security more generally was a prominent theme in remarks made during the press conference. Pompeo said that some actors, "especially China," use coercion and other means to "undermine international rules, norms, and institutions" and "present challenges to the Alliance and to the continued peace, stability, and prosperity in the Indo-Pacific." Acting Secretary of Defense Patrick Shanahan asserted "we are not sitting back while our Chinese and Russian counterparts or competitors aim to disrupt and weaponize [the space and cyberspace domains]." Japanese Defense Minister Takeshi Iwaya listed "the current situation in [the] East and South China Sea[s]" before "the North Korean issue" in his description of concerns about the region's security environment.96

2015 Revision of the Guidelines for U.S.-Japan Defense Cooperation and Establishment of the Alliance Coordination Mechanism

As noted above, in 2015 the SCC released a major revision to the alliance's guidelines for U.S.-Japan Cooperation. The new guidelines account for developments in military technology, improvements in interoperability of the U.S. and Japanese militaries, and the complex nature of security threats in the 21st century. For example, the revised guidelines address bilateral cooperation on cybersecurity, the use of space for defense purposes, and ballistic missile defense, none of which were mentioned in the 1997 version. The revised guidelines also lay out a framework for bilateral, whole-of-government cooperation in defending Japan's outlying islands. They also significantly expand the scope of U.S.-Japan security cooperation to include defense of sea lanes and, potentially, Japanese contributions to U.S. military operations outside East Asia.

One of the components of the new guidelines is the establishment of the Alliance Coordination Mechanism (ACM), a whole-of-government standing arrangement that involves participants from all the relevant agencies in the U.S. and Japanese governments as the main body for coordinating an alliance response to any contingency. The ACM is in part an effort to compensate for the absence of an integrated command structure for the alliance; other U.S. alliances, including NATO and the U.S.-South Korea alliance, have an integrated command structure.97 The ACM—a virtual group connected via phone, email, and video teleconferencing rather than a static physical entity—was designed to be flexible and responsive to a variety of contingencies.98 Its predecessor, the Bilateral Coordination Mechanism, only would have assembled in a state of war, leaving the alliance without a formal mechanism to coordinate military activities during crises or incidents short of war, such as "gray zone" conflicts (see "Preparation for "Gray Zone" Contingencies" section below) or disasters like the 2011 triple disaster (earthquake, tsunami, and nuclear meltdown) in northeast Japan.

Progress on the implementation of the new guidelines has been mixed. The ACM has been utilized (including during a 2016 North Korean nuclear test, a 2016 earthquake, and a 2016 incident involving Chinese vessels "swarming" near the Senkaku Islands), but reportedly it has not yet had the opportunity to test its full range of decisionmaking mechanisms, and some observers question whether it will be able to coordinate alliance actions in an actual military conflict.99 A key weakness of the ACM, according to one independent review of U.S. defense strategy in the region, is that "it lacks the command and control elements necessary for a rapid combined and joint response to … the type of complex, high-intensity warfare that the allies must be prepared to conduct."100 Implementing and institutionalizing other goals set in the guidelines—such as conducting cross-domain operations and building space and cyberspace defense capabilities—likely will be difficult and slow. These challenges notwithstanding, substantial progress in other areas, such as ballistic missile defense, has been made in recent years.

Progress on Implementing the Defense Policy Review Initiative

The SCC established the Defense Policy Review Initiative (DPRI) in 2002 with the aim of drawing down the U.S. military presence in Okinawa, enhancing alliance interoperability and communication, and generally expanding the alliance's ability to meet the challenges of an evolving security environment. A 2006 "Realignment Roadmap" and subsequent 2012 update outline the interrelated initiatives of the DPRI.101 Implementation of the DPRI has been uneven. While many DPRI objectives have been completed or partially completed, the most ambitious and complex objectives face significant delays.

Progress on DPRI implementation includes:

  • Partial return to Okinawa of land used by U.S. forces at Camp Zukeran, the Makiminato Service Area, and MCAS Futenma (as well as the return of approximately 4,000 hectares of the Northern Training Area, separate from the DPRI process). Land return has not begun at other designated sites for land return, such as Camp Kuwae, Naha Port, and the Army POL Depot Kuwae Tank Farm;102
  • Establishment of a Joint Operations Coordination Center at Yokota Air Base;103
  • Relocation of U.S. Carrier Wing Five from Atsugi Naval Air Base to Iwakuni;104
  • Relocation of Japan Air Self-Defense Force command facilities to Yokota Air Base;105
  • Partial shared use of facilities by U.S. and Japanese forces, implemented at Camp Hansen and ongoing at Kadena Air Base;106
  • Establishment of U.S. Army Japan I Corps Forward at Camp Zama;107
  • Relocation of Japan's Ground Self-Defense Force Central Readiness Force headquarters to Camp Zama;108
  • Construction of facilities, land return, and joint use at Sagami General Depot;109 and
  • Partial return of airspace over Yokota Air Base.110

This progress notwithstanding, the centerpiece of the DPRI—the controversial relocation of U.S. marines from MCAS Futenma in Okinawa—has been beset by delays (see "Okinawa-Guam Realignment and the Futenma Base Controversy" section below for more on the Futenma relocation). A 2017 U.S. Government Accountability Office report found several deficiencies in DOD's planning for these realignment initiatives, and concluded, "If DOD does not resolve the identified capability deficiencies … the Marine Corps may be unable to maintain its capabilities or face much higher costs to do so."111

Figure 4. Map of U.S. Military Facilities in Japan

Source: Map Resources. Adapted by CRS.

Notes: MCAS is the abbreviation for Marine Corps Air Station. NAF is Naval Air Facility.

March 2011 Earthquake and Tsunami: U.S.-Japan Alliance Performance

Appreciation for the U.S.-Japan alliance among the Japanese public increased after the two militaries worked effectively together to respond to a devastating natural disaster. On March 11, 2011, a magnitude 9.0 earthquake jolted a wide swath of Honshu, Japan's largest island. The quake, with an epicenter located about 230 miles northeast of Tokyo, generated a tsunami that pounded Honshu's northeastern coast, causing widespread destruction and killing over 16,000 people. Years of joint training and many interoperable assets facilitated a large-scale, integrated alliance effort. "Operation Tomodachi," using the Japanese word for "friend," was the first time that Self-Defense Forces (SDF) helicopters used U.S. aircraft carriers to respond to a crisis. The USS Ronald Reagan aircraft carrier provided a platform for air operations as well as a refueling base for SDF and Japan Coast Guard helicopters. Other U.S. vessels transported SDF troops and equipment to the disaster-stricken areas. Communication between the allied forces functioned adequately, according to military observers. For the first time, U.S. military units operated under Japanese command in actual operations. Specifically dedicated liaison officers helped to smooth communication. Although the U.S. military played a critical role, the Americans were careful to emphasize that the Japanese authorities were in the lead. DOD committed an estimated $88.5 million in assistance for the disasters, out of a total of over $95 million from the U.S. government.

Within 8 days of the earthquake, the SDF had deployed 106,200 personnel, 200 rotary and 322 fixed-wing aircraft, and 60 ships. Nearly all of the Maritime Self-Defense Force (MSDF) ships were transferred to the affected area, and forces from distant provinces were mobilized. After rescuing nearly 20,000 individuals in the first week, the troops turned to a humanitarian relief mission in the displaced communities, in addition to supporting activities at the troubled nuclear reactors. U.S. military troops and assets were deployed to the affected areas within 24 hours of the earthquake. At the peak, approximately 24,000 U.S. personnel, 189 aircraft, and 24 Navy vessels were involved in the humanitarian assistance and relief efforts. Major assets in the region were redirected to the quake zone, including the USS Ronald Reagan Carrier Strike group.

The successful bilateral effort had several important consequences. First, it reinforced alliance solidarity after a somewhat difficult period between 2009 and 2010 of public disagreement over the Futenma base issue. It was also well received by the Japanese public, leading to exceptionally high approval ratings of both the SDF performance and the U.S. relief efforts. The operation demonstrated to other countries the capability of the alliance. It also illuminated challenges that the two militaries might face if responding to a contingency in the defense of Japan in which an adversary were involved, including having more secure means of communication as multiple agencies and services mobilized resources.112

International Operations and Cooperation

The 1997 iteration of the Guidelines for U.S.-Japan Defense Cooperation outlined rear-area support roles that Japanese forces could play to assist U.S. operations in the event of a conflict in areas surrounding Japan. The passage of legislation in Japan since 2001 has allowed Japanese forces to take on more active noncombat roles, including in Iraq and in the Indian Ocean, under the category of international peace cooperation activities. In April 2019, two SDF personnel deployed for the country's first overseas peacekeeping mission outside the auspices of the U.N., to the Multinational Force and Observers command monitoring the cease-fire between Israel and Egypt on the Sinai Peninsula.113 The SDF has gained experience in peacekeeping, humanitarian relief and reconstruction, antipiracy, and disaster relief operations from several international deployments, including in and around Iraq in 2004-2009, Indonesia in the wake of a 2004 tsunami, Haiti after a 2010 earthquake, the Philippines after a 2013 typhoon, West Africa after a 2014 Ebola virus outbreak, Southeast Asia after the disappearance of Malaysian Airlines Flight 370, Indonesia after the 2015 crash of AirAsia Flight 8501, Nepal after a 2015 earthquake, New Zealand after a 2016 earthquake, and several U.N. missions around the world. Some prominent Japanese defense specialists have argued that noncombat missions—considered more politically acceptable to the Japanese public—are the most promising areas for the SDF to gain more experience and contribute to global security.

Aside from peacekeeping operations, antipiracy patrols in the Gulf of Aden off the coast of Somalia constitute the SDF's only current long-term overseas military deployment. Japan's Maritime Self-Defense Force (MSDF) has been engaged in antipiracy activities in the Gulf of Aden since 2009. As of May 31, 2018, Japanese vessels and P-3C patrol aircraft have escorted 3,826 ships and conducted 1,951 surveillance flights.114 Roughly 110 SDF support and headquarters personnel are stationed at a base constructed in 2011 in Djibouti. Although the Djibouti facility is Japan's first and only overseas base since World War II, the move has sparked little controversy among the Japanese public.

In addition to expanding the geographic scope of SDF operations over the years, Japan also is strengthening bilateral and multilateral defense and security cooperation with other countries, particularly in the Asia-Pacific region. As noted previously, Japan is especially invested in capacity-building for ASEAN, with which it holds several security dialogues to advance cooperation on issues like transnational crime, terrorism, cybersecurity, defense cooperation, maritime security, peacekeeping, and nonproliferation.115 In 2016, Tokyo unveiled its "Vientiane Vision" for defense cooperation with ASEAN, with an emphasis on the promotion of international law (especially in the maritime realm), capacity-building in fields like humanitarian assistance and disaster relief, defense equipment and technology cooperation, combined training and exercises, and human resource development and exchange.116 Japan began implementing programs under the Vientiane Vision in 2017.117

Japan also has robust defense relationships with Australia, India, South Korea, and the UK. In the past decade, Japan has made particular efforts to enhance and institutionalize security cooperation with Australia and India, including through an acquisition and cross-service agreement with Australia and defense technology transfer agreements with both countries. Japan is party to an Australia-Japan-U.S. trilateral dialogue and an India-Japan-U.S. trilateral dialogue as well. Prime Minister Abe has advocated for greater quadrilateral Australia-India-Japan-U.S. cooperation since 2006. In 2007, the convening of a quadrilateral security dialogue provoked sharp criticism from China and later lapsed because of Australia's reluctance to antagonize Beijing, according to reports.118 In 2017 and 2018 the four countries held three consultations and committed to "[deepen] cooperation…and to continue discussions to further strengthen the rules-based order in the Indo-Pacific."119 This nascent network, known as "the Quad," nevertheless remains largely conceptual. The role it might play in regional economic, security, or political affairs is not clear, and China and ASEAN countries are concerned the group may undermine their respective interests.

Maritime Defense Cooperation

As an island nation with an increasingly complicated maritime security environment, Japan's national security interests are in large part centered in the maritime realm. The MSDF is one of the most capable navies in the world and cooperates closely with its U.S. counterpart. U.S. Navy officials have claimed that they have a closer daily relationship with the MSDF than with any other navy, conducting over 100 joint exercises annually. During the Cold War, the U.S. Navy and MSDF developed strong combined antisubmarine warfare cooperation, which played a key role in countering the Soviet threat in the Pacific. The navies also protect key sea lines of communication (SLOCs), and 2015 legislation reinterpreting the Japanese constitution to allow the SDF to provide "collective self-defense" for its allies enables the MSDF to defend allied vessels in international waters. Since this legislation went into effect in 2016, the SDF deployed assets to defend or escort U.S. ships or aircraft 18 times, according to Japanese media.120 The most significant help extended by Japan in support of U.S. operations has come from the MSDF: refueling coalition vessels in the Indian Ocean active in Operation Enduring Freedom and, at times, an Aegis destroyer escort; the dispatch of several ships, helicopters, and transport aircraft to assist in disaster relief after the 2004 Indian Ocean tsunami; participation in the Proliferation Security Initiative (PSI) multinational exercises; and the deployment of MSDF vessels for antipiracy missions off the coast of Somalia.

The Japan Coast Guard (JCG), which is housed under the Ministry of Land, Infrastructure, Transport and Tourism rather than the Ministry of Defense, plays an important role in strengthening Japan's maritime law enforcement capabilities and since 2001 has been tasked with the mission of patrolling and guarding waters near disputed territories, including the Senkakus.121 As such, the JCG is on the "front lines" of encounters with Chinese vessels near the disputed islands, and would be the first official Japanese entity to respond to gray-zone contingencies at sea. Other JCG missions include "maintaining maritime order," search and rescue, preparing for and responding to disasters, ocean exploration, ensuring maritime traffic safety, protecting the marine environment, and international cooperation.122 JCG protection of Japanese waters and participation in international exercises and security fora is more politically palatable than MSDF participation, both to the Japanese public and to foreign countries.123 As the maritime standoff with China over the disputed islets became more intense after 2010, coordination between the MSDF and JCG improved markedly, though many challenges to interoperability remain.124

The U.S. Coast Guard conducts operations throughout the Asia-Pacific and has maintained a presence at the Yokota Air Base in Japan since 1994. In addition to conducting maritime law enforcement (such as in March 2019, when the U.S. Coast Guard cutter Bertholf assisted in the enforcement of U.N. Security Council resolutions against illicit North Korean ship-to-ship transfers of oil in the East China Sea125), the U.S. Coast Guard regularly cooperates with the JCG through various exchanges, exercises, and agreements. The JCG cooperates with other regional coast guards as well, and is a founding member of the North Pacific Coast Guard Forum (the other members are Canada, China, South Korea, Russia, and the United States).126

Proposals to Base a Second U.S. Aircraft Carrier in Japan

Since the early 1970s, one of the U.S. Navy's aircraft carriers has been forward homeported (i.e., forward based) at Yokosuka, Japan, near Tokyo, along with the other ships that constitute its strike group. Two studies by U.S. think tanks have proposed forward homeporting a second Navy carrier in the Western Pacific, either in Japan or another location. A November 2015 report by the Center for Strategic and Budgetary Assessments (CSBA) that examined options for Navy force posture and shipbuilding stated that forward deploying an additional carrier in the Western Pacific could reduce the Navy's overall carrier force-level requirement from 11 to 9, or increase U.S. naval presence across all Navy operating areas.127 A congressionally mandated report by the Center for Strategic and International Studies (CSIS) on U.S. defense strategy in the Asia-Pacific region also recommended forward homeporting a second carrier west of the international date line. The January 2016 CSIS report notes that homeporting a carrier would send a strong signal of U.S. commitment to Asia-Pacific security, but that benefit should be balanced with the risk of deploying the carrier "inside increasingly contested areas of the Western Pacific."128

DOD has from time to time studied the option of homeporting a second carrier somewhere in the Western Pacific, and to date has decided against doing so. Japan is not the only possible location for homeporting a second carrier in the Western Pacific (other possible locations include Hawaii, Guam, Australia, and perhaps Singapore), and the Western Pacific is not the only region where a second Navy carrier could be forward-homeported. There are numerous military, budgetary, and political factors that may be considered in assessing whether to homeport a second carrier in Japan or some other location. The issue of carrier forward homeporting was examined by CRS in reports in the 1990s; the general considerations discussed in those reports remain valid.129 For a proposal to homeport a second carrier in Japan, specific factors to consider would include support for the idea among Japanese political leaders and the Japanese public, and the question of where in Japan the carrier's air wing would be based.

Ballistic Missile Defense Cooperation130

Many analysts see U.S.-Japan efforts on BMD as the most robust aspect of bilateral security cooperation. DOD's 2019 Missile Defense Review states that "Japan is one of our strongest missile defense partners."131 The two countries have cooperated closely on BMD technology development, conducting joint research projects as far back as the 1980s. Largely in response to the growing ballistic missile threat from North Korea, the cabinet of Prime Minister Junichiro Koizumi decided in 2003 to acquire BMD systems for national defense. Japan's purchases of U.S.-developed technologies and interceptors after 2003 give it a highly potent BMD capability.132 The SDF has 24 PAC-3 units deployed across the Japanese archipelago and six vessels with Aegis BMD systems and SM-3 Block IA interceptors, and has plans to eventually field eight Aegis BMD-capable ships as well as SM-3 Block IIA interceptors.133 Japan also operates 11 BMD-capable early warning radar systems and plans to deploy two Aegis Ashore systems. The U.S. military has deployed an undisclosed number of PAC-3 units at its bases in Japan and seven Aegis BMD-capable vessels in the surrounding seas (two of which are currently undergoing repairs). To complement the array of advanced Japanese radars, the United States has two AN/TPY-2 X-band radars in Japan.

The mature U.S.-Japan partnership in BMD is a key driver of improvements to alliance coordination and interoperability. Both nations feed information from a variety of sensors to create a common operating picture at the Bilateral Joint Operating Command Center at Yokota Air Base, located outside Tokyo. This information-sharing arrangement improves the effectiveness of each nation's target identification, tracking, and interceptor cueing. North Korea's long-range missile launches have provided opportunities for the United States and Japan to test their BMD systems in real-life circumstances. The two countries also conduct combined and joint BMD exercises, as well as joint development and testing of an advanced SM-3 Block IIA interceptor, which Japan expects to acquire and deploy in Japan's FY2021.134

Despite recurring political tension between Seoul and Tokyo that prevents more sophisticated integration, trilateral U.S.-Japan-South Korea cooperation on countering the North Korean threat has been ongoing since the 1990s. The Trilateral Information Sharing Arrangement Concerning Threats Posed by North Korea, signed in 2014, and the Japan-ROK GSOMIA that entered force in 2016 serve as a framework for securely sharing information, including about North Korean nuclear and missile threats.135 The three countries conducted two missile tracking exercises in 2017. During trilateral talks that year, Chairman of the U.S. Joint Chiefs of Staff General Joseph F. Dunford remarked the three countries have "improved trilateral ballistic missile defense capability over the past two years." He also stated the countries would "conduct routine exercises" over the next year "to ensure we have a coherent collective response to ballistic missile defense."136 Two such exercises appear to have been conducted since then.137

Extended Deterrence

Growing concerns in Tokyo about North Korean nuclear weapons development and China's modernization of its nuclear arsenal spurred renewed attention to the U.S. policy of extended deterrence, commonly known as the "nuclear umbrella." The United States and Japan initiated the bilateral Extended Deterrence Dialogue in 2010, recognizing that Japanese perceptions of the credibility of U.S. extended deterrence were critical to its effectiveness. The dialogue is a forum for the United States to assure its ally and for both sides to exchange assessments of the strategic environment. The views of Japanese policymakers (among others) influenced the development of the 2010 U.S. Nuclear Posture Review (NPR).138 Japan welcomed the Trump Administration's 2018 NPR, with the Ministry of Foreign Affairs stating,

Japan highly appreciates the latest NPR which clearly articulates the U.S. resolve to ensure the effectiveness of its deterrence and its commitment to providing extended deterrence to its allies including Japan, in light of the international security environment which has been rapidly worsened since the release of the previous 2010 NPR, in particular, by continued development of North Korea's nuclear and missile programs.139

Japanese leaders have repeatedly rejected developing their own nuclear weapon arsenal. Although Japan is a ratified signatory to the Treaty on the Non-Proliferation of Nuclear Weapons, and Japanese public opinion is largely antinuclear, a lack of confidence in the U.S. security guarantee could lead Tokyo to reconsider its own status as a nonnuclear weapons state. Then-candidate Trump in spring 2016 stated that he was open to Japan (and South Korea) developing its own nuclear arsenal to counter the North Korean nuclear threat.140 Analysts point to the potentially negative consequences for Japan if it were to develop its own nuclear weapons, including significant budgetary costs; reduced international standing in the campaign to denuclearize North Korea; the possible imposition of economic sanctions that would be triggered by leaving the global nonproliferation regime; potentially encouraging South Korea and/or Taiwan to develop nuclear weapons capability; triggering a counterreaction by China; and in creating instability that could lessen Japan's economic and diplomatic influence in the region. For the United States, analysts note that encouraging Japan to develop nuclear weapons could mean diminished U.S. influence in Asia, the unraveling of the U.S. alliance system, and the possibility of creating a destabilizing nuclear arms race in Asia.141

Japan plays an active role in extended deterrence through its BMD capabilities. Whereas prior to the introduction of BMD Japan was entirely reliant on the U.S. nuclear deterrent, it now actively contributes to extended deterrence.142 In the future, Japan may develop a conventional strike capability with the intent to augment extended deterrence.143 (See section on "Japan's Pursuit of Offensive Capabilities," below.) Japanese diplomatic support for nuclear nonproliferation is another element of cooperation to reduce nuclear threats over the long term.

U.S. Arms Sales to Japan

Japan has been a major purchaser of U.S.-produced defense equipment and has the status of a NATO Plus Five country.144 Between 2009 and 2018 Japan was one of the top 10 recipients of actual deliveries of major conventional weapons from the United States, spending an average of $363.9 million USD per year, which accounts for between 83% and 97% of Japan's arms imports, according to estimates from the Stockholm International Peace Research Institute.145 Separate analysis suggests that Japan under Abe has significantly increased its use of DOD's Foreign Military Sales (FMS) program, jumping from an average of about 76 billion JPY ($690 million USD) in the six years prior to his return to power in 2012 to an average of 339 billion JPY ($3.08 billion USD) in the six years afterward.146 The SDF has more equipment in common with the U.S. military than does any other allied military, according to U.S. defense officials in Japan. In 2016, the United States and Japan signed a Reciprocal Defense Procurement Agreement, which allows foreign and domestic companies to compete for defense contracts in both countries on equal terms by removing protectionist conditions. Japanese companies domestically manufactured some equipment under license from U.S. companies, including sophisticated systems like the F-15J and F-15SDJ fighter aircraft in the 1980s and 1990s,147 and more recently the F-35A (however, that production may be scaled back to maintenance, repair, overhaul, and upgrade services in the 2020s).148 Other equipment is purchased "off the shelf" from U.S. companies.

According to then Japanese Minster of Defense Takeshi Iwaya, Japan's FY2020 draft budget included $6.4 billion for FMS transfers from the United States, which he said was "the largest amount ever and about a 70% increase compared to the previous year."149 In recent years, the United States has authorized numerous high-profile purchases of U.S. defense equipment through the FMS program by Japan, such as

  • F-35 Joint Strike Fighters (42 short take-off and vertical landing aircraft for $10 billion in 2012; Japan announced in December 2018 it plans to buy 105 F-35As);
  • E-2D "Hawkeye" airborne early warning and control aircraft (4 for $1.7 billion in 2015 and 9 for $3.135 billion in 2018);
  • Aegis Weapon Systems (2 for $1.5 billion in 2015 and 2 for $2.15 billion in 2019);
  • V-22B "Osprey" tilt-rotor aircraft (17 for $3 billion in 2015);
  • KC-46A "Pegasus" aerial refueling tankers (4 for $1.9 billion in 2016);
  • RQ-4 "Global Hawk" unmanned aerial vehicles (UAVs) (3 for $1.2 billion in 2015); and
  • various missiles (combined value of over $3 billion since 2010).150

Further, the State Department indicated Japan has been approved for more than $16 billion in direct commercial sales (DCS) of military articles, such as aircraft, electronics, missiles, and parts between January 1, 2013 and September 30, 2018.151 (The approval of sales for both the FMS and DCS programs does not indicate whether Japan purchased the full value).

Defense Technology Cooperation and Coproduction

In recent years, the United States and Japan have begun to explore deeper defense industry cooperation and coproduction of weapons systems. The 2015 revised Guidelines for U.S.-Japan Defense Cooperation feature a section titled "Bilateral Enterprise," which describes the two allies' intention to "cooperate in joint research, development, production, and test and evaluation of equipment and in mutual provision of components of common equipment and services."152

For example, technological cooperation on BMD in the 1990s and 2000s led to an agreement to jointly produce the next generation of missile interceptors for the Aegis Weapon System, the SM-3 Block IIA. This cooperative development program is still running, having completed two successful interception tests, one in February 2017 and one in October 2018 (two other tests failed).153 To make this cooperation a reality, the Japanese government committed to allowing transfers of the SM-3 Block IIA to third parties in the June 2011 SCC Joint Statement, an important concession that Washington had requested. That decision meant that the Japanese government had to relax its self-imposed restrictions on arms exports, which date back to 1967, paving the way for other coproduction arrangements. Japan's "Three Principles on Arms Exports" (the so-called 3Ps) prevented arms transfers to Communist countries, those sanctioned by the U.N., and countries "involved or likely to be involved in international conflicts."154 In 2014 those principles were modified to become the "Three Principles on Transfer of Defense Equipment and Technology," which provide a more nuanced set of guidelines to distinguish prohibited transfers from cases for which "strict examination and appropriate control" are required—notably when such a transfer "contributes to active promotion of peace contribution and international cooperation."155

The new principles now allow Japanese firms to participate in the production of parts for the F-35 Joint Strike Fighter and to enable defense equipment exports. Tokyo has concluded that the prior restrictions unduly limited Japan's participation in coproduction of arms (e.g., the F-35) and prevented arms transfers that were expected to contribute to international security. Since 2013 Japan has also extended defense equipment and technology cooperation by signing transfer agreements with a handful of other countries including the United Kingdom, France, Germany, Italy, Australia, India, and Malaysia. Notably, Japan has begun a limited amount of arms exports to ASEAN nations as part of the Vientiane Vision (see "International Operations and Cooperation" section above). This has included a transfer of five MSDF TC-90 training aircraft to the Philippine Navy between 2017 and 2018, with plans to transfer additional retired equipment.156 In 2015, Japan aimed to expand its role as a major high-end arms supplier when it submitted a high-profile bid to design and jointly produce Australia's next submarine fleet in a deal valued between $35 billion and $40 billion USD, though it ultimately lost out to France.157

Okinawa-Guam Realignment and the Futenma Base Controversy

Due to the legacy of the U.S. occupation and the island's key strategic location, Okinawa hosts a disproportionate share of the U.S. military presence in Japan. Despite comprising less than 1% of Japan's total land area, Okinawa hosts over half of the more than 54,000 U.S. military personnel stationed in Japan and about 70% of all facilities and areas used exclusively by USFJ. Among these facilities is Kadena Air Base, a hub of the U.S. presence in the Pacific. Kadena is considered by many to be critical for the most likely U.S. military contingencies in Asia and as a hub of the U.S. presence in the Pacific.158

Many native Okinawans chafe at the large U.S. military presence, reflecting in part the tumultuous history and complex relationships with "mainland" Japan and with the United States. Although the views of Okinawans are far from monolithic, many Okinawans—including those who largely support the U.S.-Japan alliance—have concerns about the burden of hosting foreign troops, particularly about issues like crime, safety, environmental degradation, and noise. Because of these widespread concerns among Okinawans, the long-term prospect for the U.S. military presence in Okinawa remains a challenge for the alliance.159

In 1996, the SCC established the Special Action Committee on Okinawa (SACO) to address the concern that the basing situation may not be politically sustainable. The issue had become particularly charged because of the rape of a 12-year-old Okinawan girl by three U.S. servicemembers in 1995. The 1996 SACO Final Report mandated the return to Okinawa of thousands of acres of land used by the U.S. military since World War II, including by moving MCAS Futenma from crowded Ginowan City to Camp Schwab in Nago City's less congested Henoko area.

Efforts to implement the Okinawa agreement, however, quickly stalled due to local opposition, as protests against the planned Futenma Replacement Facility and Okinawan leaders presented steep challenges to implementing the 1996 plan. This led to the 2006 U.S.-Japan Roadmap for Realignment and the Defense Policy Review Initiative, still ongoing. The United States agreed to remove roughly 8,000 marines from Okinawa to Guam by 2014. Congressional concerns over the scope and cost of the Guam realignment, as well as concerns about Guam's preparedness, led to later revisions that adjusted the number of personnel and dependents to be relocated. After years of delays and legal disputes between Tokyo and Okinawa, culminating in a Japanese Supreme Court decision, land reclamation activities for the Futenma Replacement Facility's runway began in mid-December 2018. Uncertainty remains about the cost and timeframe of the project. Japan's Ministry of Defense originally estimated in 2013 the project would take about 5 years and cost 231 billion yen (about $2.1 billion at current exchange rates); in late 2018 the Okinawan government asserted that it was likely to take 13 years and cost around 2.5 trillion yen (about $22.7 billion).160

Both Japanese and U.S. officials have repeatedly declared the intent to return the land of MCAS Futenma to local control as soon as possible. U.S. military officials, including the Commander of the U.S. Pacific Command (now U.S. Indo-Pacific Command) in congressional testimony, stated that operations would not cease at Futenma until a replacement facility on Okinawa is completed.161 Japanese officials are hopeful that land returns from vacated U.S. bases will spur economic development on Okinawa and ease opposition to the U.S. base plans. In December 2016, the United States returned nearly 10,000 acres of land to Japan, the largest transfer of land since the reversion of Okinawa to Japan in 1972.

U.S.-Japan Cobasing Remains Elusive

Although the U.S. military and SDF have some colocated command facilities, such as at the Bilateral Joint Operations Command Center at Yokota Air Base, the two militaries do not share base facilities in Japan on a large scale. Various commentators have recommended that the joint use of military bases could more fully integrate operations, ease some of the burden on hosting communities, and build more popular support for the alliance.162 Particularly as the Japanese employ more advanced capabilities, shared use of bases could substantially enhance interoperability. Shared use of facilities on Okinawa, where the U.S. military presence is particularly controversial, could be a way for the alliance to address that enduring issue.163 Other analysts point out, however, that colocation would introduce difficult problems for the two forces, particularly in terms of understanding each other's different rules of engagement. Japan's constitutional restrictions on use of force contrast starkly with the U.S. military's more flexible doctrine, including the use of preemptive force.164 In addition, Japanese officials would need to reconcile the fact that U.S. military forces operate under the terms of the Status of Forces Agreement, whereas SDF troops are subject to domestic laws.

Evolution of Japanese Defense Policy

As Japan's defense policy and capabilities have expanded, so has the SDF's ability to contribute to the alliance and to U.S. military operations and capabilities in the region. As such, U.S. defense officials have welcomed and encouraged this shift. U.S. and Japanese officials, as well as observers of the alliance, often point out that U.S. and Japanese policy and strategy documents are increasingly aligned.165

In December 2018, Japan released a pair of documents that are intended to guide its national defense efforts, including its defense budget, over the next decade—the National Defense Program Guidelines for FY2019 and Beyond and the Medium Term Defense Program (FY2019-FY2023).166 The National Defense Program Guidelines (NDPG) have roots dating back to the middle of the Cold War, when Japanese defense posture was based on the idea of resisting a Soviet invasion from the north. The first NDPG was established in 1976 with a concept of "Basic Defense Capability" aimed to maintain the minimum necessary defense force needed to prevent a regional power vacuum, rather than to defend again a direct military threat.167

The collapse of the Soviet Union in 1991 removed the basis for this policy, but Japan's defense posture initially was slow to evolve (see the Appendix for historical background). The 1976 NDPG was replaced in 1995, adding response to "contingencies such as major disasters" and "building a more stable security environment" to the roles of defense.168 This addition was in response to major events such as the 1995 Great Hanshin Earthquake that destroyed much of the city of Kobe, as well as a law passed in 1992 to allow U.N. peacekeeping operations (PKOs). Although Japan began participating in PKOs and rear-area support for the United States in regional contingencies, Japanese strategic culture remained reactive and risk-averse.

In more recent years, Japanese defense policy has become more assertive and flexible as a result of the changing security environment. In response to new threats in the 2000s, including international terrorism and new ballistic missiles threats, the NDPG was again revised in 2004 to allow for the "capability to work independently and proactively on implementing international peace cooperation activities, as well as dealing effectively with new threats and diverse contingencies." In the second Abe administration, in 2013, the NDPG was revised as part of a broader set of defense reforms between 2013 and 2015 that also included the establishment of the National Security Council, passage of a secrecy protection law designed to meet American prerequisites for closer military cooperation, and legal changes to allow for collective self-defense, as well as the revised bilateral defense guidelines. 169Additionally, a central concept in the 2010 NDPG (which was drafted under the DPJ when it was in power for three years, reflecting the widespread support for an expanded SDF role) that helped distinguish it from previous iterations was that of a "Dynamic Defense Force," which was further shifted into a "Dynamic Joint Defense Force" under the 2013 NDPG.170 The most recent 2018 guidelines transformed the concept into that of a "Multi-Domain Defense Force," described in more detail below.171

Although some defense policy changes were sudden and unexpected, the trajectory since the end of the Cold War has consistently been toward a more capable SDF and deeper cooperation with the U.S. military. In addition to an evolving assessment of the security environment, other drivers of this evolution include a growing sense of insecurity among Japanese elites; the gradual erosion of anti-militarist norms under strong, conservative political leaders focused on defense policies; positive experiences of SDF participation in international security and HA/DR missions; and the mutual Japanese and American desire to share the burden of maintaining regional security and stability. The defense reforms initiated by the Abe administration in 2013-2015 have encouraged Japanese officials to be less cautious and more proactive in developing and carrying out Japan's security policies.172

Japan's Pursuit of Offensive Capabilities

The traditional division of labor between the allies, with the United States as the "spear" and Japan as the "shield," appears to be shifting as Japan acquires more offensive military capabilities. Although Japan has interpreted its constitution to permit the maintenance of a military for self-defense purposes only, in recent years it has decided to acquire offensive (or potentially offensive) capabilities, the most consequential—and controversial—of which are conventional offensive strike capabilities (often referred to in Japan as "counterstrike" capabilities). Among the offensive (or potentially offensive) systems that Japan's Medium Term Defense Program (FY2019-FY2023) describes pursuing are stand-off missiles such as Joint Strike Missiles, extended-range Joint Air-to-Surface Standoff Missiles, and Long-Range Anti-Ship Missiles; hypersonic boost-gliders; hypersonic cruise missiles; some cyber capabilities; some counterspace capabilities; as well as the conversion of the Izumo-class destroyer from a "helicopter carrier destroyer" to an aircraft carrier capable of launching F-35Bs.173

Japan has not adopted conventional offensive strike as a mission, though it is exploring the option (and acquiring platforms like stand-off missiles) that would enable a limited strike capability.174 In 2017 and 2018, an LDP research commission comprised of retired high-level defense officials and experts proposed that Japan consider the acquisition of capabilities to hit enemy missile bases for use in retaliatory strikes.175 For the time being, a strict division of labor between the allies remains, with the United States responsible for offensive strike, and Japan responsible for defensive operations. The 2015 U.S.-Japan Defense Cooperation Guidelines delineates these roles thus: "The United States Armed Forces may conduct operations involving the use of strike power, to support and supplement the Self-Defense Forces. When the United States Armed Forces conduct such operations, the Self-Defense Forces may provide support, as necessary."176 Japan's August 2018 defense white paper echoes this, saying the SDF "may provide support, as necessary, for the strike operations of the United States Armed Forces" while the United States may use strike power "to support and supplement SDF."177

2018 National Defense Program Guidelines

With concerns over China and North Korea at its heart, the 2018 NDPG (for Japanese Fiscal Years 2019 and beyond) articulates a continued dual strategy of strengthening Japan's own defense program while strengthening security cooperation with the United States and other countries. Yet, the 2018 NDPG shows stark shifts in content from previous iterations. The guidelines openly acknowledge "Japan's security environment is becoming more testing and uncertain at a remarkably faster speed than expected when the 'National Defense Program Guidelines for FY 2014 and beyond'... was formulated." Suggesting that Japan may be ready to bear more responsibility within the alliance for its own defense, the document newly emphasizes Japan's own defense efforts over the security cooperation with the United States, stating upfront that as a matter of national sovereignty "Japan's defense capability is the ultimate guarantor of its security.... "178 The document calls for enhancing capabilities in the traditional security domains (land, air, and sea), such as with increasing the use of unmanned vehicles and operationally flexible Short Take-Off and Vertical Landing (STOVL) fighter aircraft. At the same time, the guidelines place increasing importance on the "new domains" of defense—space, cyberspace, and the electromagnetic spectrum—and the need for enhanced capabilities in cross-domain operations by building a "multi-domain defense force." The new domains (specifically cyberspace and outer space) had been raised in previous iterations of the guidelines, but not in detail.

The supplementary 2018 Medium Term Defense Program lays out a more detailed picture of intended security activities.179 The program projects a five-year expenditure plan that would cost ¥25,500 billion (or $232 billion) after taking into consideration planned cost-saving measures.180 As previously noted (see "Fiscal Constraints" section) the actual rates of increase have yet to carry the Japanese defense budget outside the Japanese postwar tradition of spending 1% of GDP on defense.

The 2018 Medium Term Defense Program provides indications of where the majority of the increased budget will be spent—mostly on more up-to-date weapons technology, such as through continued upgrades to old F-15 jets, replacement of F-15s with F-35As, and introduction of STOVL F-35Bs. One major expense is the planned procurement of a new type of destroyer and the retrofitting of Izumo-class helicopter carrier destroyers to accommodate F-35B fighters. Further, the program calls for the procurement of a variety of missiles and BMD systems. In this area Japan has already, for example, agreed to expand its Aegis BMD systems at a reported cost of $2.15 billion, announced plans to build new medium- and long-range cruise missiles, and even agreed to a much smaller purchase of joint strike missiles that would give Japan land-attack capabilities from the air for the first time. While the Program does call for "reorganization of the major SDF units," personnel levels are expected to remain largely consistent through FY2023 with levels reported in the 2014 guidelines—up by about 3% since the 2000s.

"Multi-Domain Defense Force" Concept

The 2010 NDPG, as previously noted, signaled a definitive shift away from the Cold War security framework based on countering Soviet threats, particularly in areas around Northern Japan, to a new framework focused on the southwestern islands of the Japanese archipelago, where Japanese forces have encountered Chinese military activities and incursions. The document outlined a new "dynamic defense force" concept that emphasizes operational readiness and mobility to enhance deterrence, as well as cooperation with allies and partners in the Asia-Pacific. The 2010 NDPG also explicitly identified China's military modernization and lack of transparency as concerns for the region. Building on the 2010 NDPG, the 2013 NDPG added jointness—operational cooperation among the air, naval, and ground forces—as a core element. The 2013 NDPG intensified the trend of the SDF toward more mobility and resilience, directing expanded investment in more amphibious capabilities to defend Japan's remote islands as well as in BMD to protect itself from missiles, accelerating reforms to strengthen ISR capabilities, and developing more capabilities in the domains of outer space and cyberspace.

The 2018 NDPG expands the SDF's emphasis on increasing jointness to the concept of "Multi-Domain Defense," based on the "increasingly uncertain security environment" and the need for Japan to "improve quality and quantity of capabilities that support sustainability and resiliency of various activities; and develop a defense capability that enables sustained conduct of flexible and strategic activities commensurate with the character of given situations." The NDPG asserts that developing multi-domain defense will "generate synergy and amplify the overall strength, so that even when inferiority exists in individual domains such inferiority will be overcome and national defense accomplished."181 At the April 2019 SCC meetings, the United States and Japan jointly acknowledged that conducting cross-domain operations was one of the core objectives to advancing the defense relationship, and that space, cyberspace, and the electromagnetic spectrum were "priority areas to better prepare the Alliance" for such operations.182 Some observers have pointed out that jointness is still a major challenge for the SDF, despite the rhetoric about it since the 2013 NDPG.183

Separately, as part of its efforts to improve its own capabilities and to work more closely with U.S. forces, Japan established in 2007 a Joint Staff Office that puts all the ground, maritime, and air self-defense forces under a single command. Under the previous organization, a joint command was authorized only if operations required multiple service participation, which had never occurred in the history of the SDF. The need for smoother coordination with the U.S. joint command was one of the primary reasons for adopting the new organization. However, a 2016 study by CSIS found that Japanese command and control mechanisms were insufficient for waging complex, high-intensity warfare alongside U.S. forces.184

Preparation for "Gray Zone" Contingencies

Japanese leaders have been concerned that China could attempt to act on its claim to the disputed Senkaku Islands by using nonmilitary forces, such as the China Coast Guard or maritime militia, to wrest control of the islets. To address this type of "gray zone" contingency—meaning the use of force between a state of war and a state of peace—the United States and Japan have sought to develop more responsive and coordinated alliance functions for scenarios short of war, and Japan has boosted its own rapid response capabilities. One focus for bilateral cooperation has been improving ISR in volatile areas during peacetime, to prevent an adversary from surprising U.S. and Japanese leaders and achieving a fait accompli. Japanese strategists also are discussing gray zone challenges beyond the maritime realm, such as adversaries' exploitation of social media to manipulate public opinion and use of hybrid warfare.185

Attention to the Space Domain

Japan has made strides in extending its defense policies to activity in the space, cyber, and electromagnetic domains, but it lags behind the United States and East Asian neighbors in various ways. Space was the first new domain Japan started addressing. For decades, Japan has had a capable civilian and commercial space program, which currently is headed by its national space agency, the Japan Aerospace Exploration Agency. Japan's 2008 Basic Space Law permitted use of outer space (and associated technologies) for defense purposes.186 Prior to that, Japanese law confined Japan's space activities to "peace purposes," which was interpreted to mean "non-military."187 Despite this, Japan began launching reconnaissance satellites in the early 2000s in response the 1998 North Korean rocket that flew over Japan.188 As of 2018, Japan was operating four radar and two optical reconnaissance satellites.189 It was also operating two advanced communications satellites, the Kirameki 1 and 2, which were reported to allow the SDF to move away from old voice and fax information sharing methods and into larger data exchanges.190 These types of satellite upgrades allow the SDF to better monitor regional military activity, as well as respond to disasters.

In March 2013 the United States and Japan launched an annual "Japan-U.S. Comprehensive Dialogue on Space" involving multiple departments in both countries, including defense. During that first meeting they agreed to pursue a bilateral agreement on space situational awareness,191 which was signed in May of the same year.192 The revised bilateral guidelines create a framework for the two allies to cooperate on resilience of space assets. More recently it has been reported that the SDF has begun building its first space situational awareness systems with technical assistance purchased through DOD's FMS program, and the countries reportedly intend to connect systems in the future.193 At the April 2019 SCC talks, both sides jointly emphasized "the integral role of space in full spectrum cross-domain operations" and "stressed the importance of deepening cooperation on space capabilities to strengthen mission assurance, interoperability, and operational cooperation."194

Attention to the Cyber Domain

The emphasis on cyberspace has been a newer development for Japan, having become a particular concern in the early 2010s (Japan's annual defense white papers contained no reference to cybersecurity until 2010).195 Long a U.S. priority, cybersecurity now increasingly is communicated as an alliance priority as well, and Japan is taking a whole-of-government approach in its cybersecurity efforts. The first Japanese governmental efforts on cybersecurity date back to the 2000s, including with the "Action Plan to Protect Information Systems against Cyber-attacks" in 2000 and the establishment of the "Information Security Policy Council" and the "National Information Security Center"—now called the "National Center of Incident readiness and Strategy for Cybersecurity"—in 2005.196 However, these efforts were seen as weak, particularly in their lack of official power to enforce coordination across the Japanese government.

Several high-profile cyberattacks that affected Japan, the United States, and South Korea between 2009 and 2013 raised awareness of the issue, and eventually paved the way for the 2014 Basic Act on Cybersecurity (amended in December 2018), as well as the 2013 Protection of Specially Designated Secrets Law.197 Based on the Cybersecurity Act, the Japanese Cabinet Secretariat in November 2014 established a Cybersecurity Strategic Headquarters to take a central role in policy coordination and response to cybersecurity incidents. The headquarters issued a National Cybersecurity Strategy, first in 2015 and then in 2018, that bridges efforts across the Japanese government. While the 2015 strategy was formulated around the "emergence of interconnected and converged information society," the 2018 strategy focuses on the "unification of cyberspace and real space," emphasizing the threat that actions taken in cyberspace can now pose to outer space.198

The 2018 Medium Term Defense Program calls for the establishment of one joint cyber defense squadron to "fundamentally strengthen cyber defense capabilities, including capability to disrupt, in the event of attack against Japan, opponent's use of cyberspace for the attack as well as to conduct persistent monitoring of SDF's information and communications networks."199 At the same time, constitutional and legal barriers prevent SDF cyber personnel from offensive and certain defense cyber actions.200

Cybersecurity is an increasingly high-ranking priority for the alliance. In 2011 the SCC put cybersecurity, along with space, as a "common strategic objective," and agreed to a bilateral cybersecurity dialogue. Inaugurated in 2013 and led by the State Department and the Ministry of Foreign Affairs, the dialogue provides a forum for the two sides to exchange information on cyber threats and align international cyber policies.201 In 2017, Japan announced it would join the U.S. Department of Homeland Security's Automated Indicator Sharing (AIS) program.202 Most significantly, the two countries announced at the 2019 SCC meeting that "international law applies in cyberspace and that a cyber attack could, in certain circumstances, constitute an armed attack for the purposes of Article 5 of the U.S.-Japan Security Treaty"—a major clarification on the general applicably of the alliance treaty to a new domain, although which specific circumstances would fall in the category of an armed attacked were not clarified.203

Attention to the Electromagnetic Spectrum

The electromagnetic spectrum is the newest addition to the list of priority domains for Japan and the alliance; that priority largely is a response to Chinese activity and investment in the area.204 The electromagnetic spectrum is often referred to in military contexts as electronic warfare, which DOD defines as "military action involving the use of electromagnetic and directed energy to control the electromagnetic spectrum or to attack the enemy."205 The 2018 NDPG emphasizes China's "rapidly advancing capabilities ... with which to disrupt opponent's command and control." As with activities in the other new domains, developing capabilities in this area may be included in the general debate over Japan's stance as an exclusively defense-oriented nation.206

Attention to Amphibious Capabilities

While the new domains of warfare have become a priority, amphibious warfare (projecting military force from the sea onto land) has been a major emphasis of the SDF over the past decade. Prior to the 2010s, amphibious capabilities were not considered important for defending Japan and were negatively associated with offensive strategies. The territorial dispute over the Senkaku Islands now presents a plausible scenario in which Japan, possibly as part of an alliance operation, would want to retake its outlying islands from an occupying force. The challenge of delivering disaster relief to devastated areas after the March 2011 earthquake and tsunami provided another motivation for developing these capabilities.207

Japan has increased Ground Self-Defense Forces (GSDF) training exercises with the U.S. Marine Corps as it begins to develop a Marine Corps-like function within the GSDF.208 The SDF has sent warships, combat helicopters and fixed-wing aircraft, and thousands of infantry to the annual Dawn Blitz Exercise held in California. In March 2018 the GSDF launched an Amphibious Rapid Deployment Brigade in southwestern Japan with approximately 2,100 personnel (anticipated to grow to 3,000) who specialize in operating equipment such as AAV-7 amphibious vehicles and V-22 Ospreys to be the main response force for attacks on Japan's remote islands, as well as assist with disaster relief.209 Japan also recognizes the need to improve interservice jointness in order to carry out amphibious operations. As noted above, the newest MSDF flat-top destroyers, the Izumo-class, which carry up to 14 helicopters, will be converted to aircraft carriers capable of launching F-35B STOVL fighters, allowing the ships to be multipurpose in defense of Japan's southwestern islands.210

Appendix. Historical Review of the Alliance

Post-World War II Occupation

Following Japan's defeat in World War II, the Allied Powers, led by the United States, occupied the archipelago from 1945 to 1952. Occupation officials initially intended to thoroughly demilitarize Japan. The Japanese constitution, drafted by U.S. occupation officials and adopted by the Japanese legislature in 1947, renounced the use of war in Article 9, stating that "land, sea, and air forces, as well as other war potential, will never be maintained." However, as the Cold War confrontation with the Soviet Union grew, the goals of the occupation shifted to building Japan up as a strategic bulwark against the perceived Communist threat. After the outbreak of the Korean War in 1950, U.S. officials pressed for the establishment of a Japanese national paramilitary force, which in 1954 became the Self-Defense Forces (SDF). Debate about whether the existence of the SDF, which evolved in practice into a well-funded and well-equipped military, violates Article 9 continues today. Japan regained its sovereignty in 1952 after the signing of the San Francisco Peace Treaty, which officially ended the conflict and allocated compensation to Allied victims of Japanese war crimes.

Bilateral Alliance Establishment

During the Cold War, the United States increasingly viewed Japan as a strategically important ally to counter the Soviet threat in the Pacific. A Mutual Security Assistance Pact signed in 1952 was replaced by the 1960 Treaty of Mutual Cooperation and Security, in which Japan grants the United States military basing rights on its territory in return for a U.S. pledge to protect Japan's security. Unlike other defense treaties with allies, this pledge is not mutual: Japan is not obligated to defend the United States if it is attacked. A military aid program during the 1950s provided equipment deemed to be necessary for Japan's self-defense, and Japan continued to expand the SDF and contribute more money to host nation support (HNS) for U.S. forces. Under Prime Minister Shigeru Yoshida's leadership (1946-1947 and 1948-1954), Japan followed U.S. leadership on foreign and security policies and focused on economic development, a strategy that became known as the "Yoshida Doctrine."

The Yoshida Doctrine was controversial in Japan. Yoshida himself resisted U.S. officials' push for a full-scale Japanese rearmament (i.e., the establishment of a full-fledged military in name and in fact). In addition, many elements of Japanese society rejected the arrangement. For much of the 1950s, the political right tried unsuccessfully to revise or even abrogate the Constitution's Article 9 and portions of the treaty. When one of their number, Prime Minister Nobusuke Kishi, negotiated a revision to the treaty in 1960, the political left mobilized opposition to the changes. Although Kishi rammed the revisions through parliament, hundreds of thousands of protestors took to the streets in Tokyo, causing the cancellation of a visit by President Dwight Eisenhower and the resignation of Kishi and his government. (Current Prime Minister Abe is Kishi's grandson, and sees his efforts to revise Japan's Constitution, including Article 9, in part as carrying on Kishi's legacy.)

U.S.-Japan defense relations again entered a period of uncertainty because of U.S. President Richard Nixon's so-called Guam Doctrine of 1969 (which called on U.S. allies in Asia to provide for their own defense), the normalization of relations between China and the United States, and the U.S. withdrawal from Vietnam. One major irritant was resolved when Prime Minister Eisaku Sato and Nixon signed a joint communiqué that returned administrative control of the Okinawa islands to Japan in 1972, although the United States continues to maintain large military bases on the territory. The establishment of the bilateral Security Consultative Committee in 1976 led to greater defense cooperation, including joint planning for response to an attack on Japan.

Post-Cold War Adjustments

In the post-Cold War period, Japan was criticized by some in the international community for its failure to provide direct military assistance to the United Nations coalition during the Persian Gulf War in 1990-1991. Because of constitutional and policy restrictions on SDF activities abroad and domestic opposition to the war, Japan only provided financial assistance, providing over $13 billion toward U.S. military costs and humanitarian assistance. Following Japan's passage of a bill in 1992 to allow for its participation in U.N. peacekeeping operations, the SDF has been dispatched to several peacekeeping missions. Tensions over North Korea and the Taiwan Strait contributed to a revision of the U.S.-Japan Defense Guidelines in 1996-1997 by President Bill Clinton and Prime Minister Ryutaro Hashimoto that granted the U.S. military greater use of Japanese installations in time of crisis and vaguely referred to a possible, limited Japanese military role in "situations in areas surrounding Japan." That was assumed to be referring to potential U.S. conflicts in the Taiwan Strait and the Korean peninsula, although military officials insisted that the phrase was "situational" rather than geographic. North Korea's launch of a long-range Taepodong rocket over Japan in 1998 galvanized political support for undertaking joint research with the United States on ballistic missile defense.

Post-9/11 Changes

U.S. policy toward East Asia under the George W. Bush Administration took a decidedly pro-Japan approach from the outset. Several senior foreign policy advisors with extensive background in Japan took their cues from the so-called Armitage-Nye report (the lead authors were Richard Armitage, who served as Deputy Secretary of State in George W. Bush's first term, and Joseph Nye), the final paper produced by a bipartisan study group before the 2000 U.S. presidential election.211 The report called for a more equal partnership with Japan and enhanced defense cooperation in a number of specific areas.

With this orientation in place, Japan's response to the terrorist attacks of September 11, 2001, reinforced the notion of the U.S.-Japan alliance as one of the central partnerships of U.S. foreign policy, particularly in Asia. Under the leadership of Prime Minister Junichiro Koizumi, the Japanese legislature passed legislation that allowed Japan to dispatch refueling tankers to the Indian Ocean to support U.S.-led operations in Afghanistan. In February 2004, Japan sent over 600 noncombat military personnel to Iraq to assist in reconstruction activities—the first time since World War II that Japan dispatched soldiers to a country where conflict was ongoing.212 The ground troops were withdrawn in 2006. A Japanese SDF air division remained until 2008, when U.N. authorization for multinational forces in Iraq expired.

After a period of rejuvenated defense ties in the first years of the George W. Bush Administration, expectations of a transformed alliance with a more forward-leaning defense posture from Japan diminished. Koizumi's successors—Shinzo Abe, Yasuo Fukuda, and Taro Aso—each survived less than a year in office and struggled to govern effectively. Abe succeeded in upgrading the Defense Agency to a full-fledged ministry, but faltered on his pledges to create Japanese versions of the National Security Council and to pass a permanent deployment law to allow the government to dispatch SDF troops without a U.N. resolution. Fukuda, elected in September 2007, was considered a friend of the alliance, but more cautious in his security outlook than his predecessors. He also faced an empowered opposition party—the Democratic Party of Japan (DPJ)—that temporarily forced Japan to end its naval deployment of refueling ships to support U.S.-led operations in Afghanistan. Aso, who served as foreign minister in the Abe cabinet, was largely unable to pursue a more active military role for Japan due to his precarious political position. In the final years of the decade, political paralysis and budgetary constraints in Tokyo, Japan's minimal progress in implementing base realignment agreements, Japanese disappointment in Bush's policy on North Korea, and a series of smaller concerns over burden-sharing arrangements led to reduced cooperation and a general sense of unease about the partnership.

U.S.-Japan Relations Under the Obama and DPJ Administrations

The Obama Administration came into power in 2009 indicating a policy of broad continuity in its relations with Japan, although some Japanese commentators initially fretted that Washington's overtures to Beijing would marginalize Tokyo. It was changes in leadership in Tokyo, however, that destabilized the relationship for a period. In fall 2009, when the Democratic Party of Japan came into power under Yukio Hatoyama's leadership, relations with Washington got off to a rocky start because of his emphasis on lessening Japan's reliance on the United States and differences over the relocation of the Futenma Marine base (see "U.S. Military Presence in Japan and Futenma Controversy" section above). Stalemate on the Okinawa agreement had existed for several years under previous LDP governments, but the more public airing of the dispute raised concern that the alliance was eroding. In addition, the DPJ initially advocated a more Asia-centric foreign policy, which some observers interpreted as a move away from the United States.

After months of intense deliberation with the United States and within his government, Hatoyama eventually agreed to move ahead with the relocation. However, the political controversy surrounding the Futenma issue played a major role in his decision to resign in June 2010. The fall of Hatoyama demonstrated to Japanese leaders the political risks of crossing the United States on a key alliance issue. His successor, Prime Minister Naoto Kan, looked to mend frayed relations and stated that his administration supported the agreement. The overwhelming allied response to the March 2011 disaster in Tohoku buoyed alliance relations. By the time that Yoshihiko Noda, Kan's successor finished his term in December 2012, American policymakers had regained confidence in Tokyo's alliance management approach. After Hatoyama, DPJ leaders appeared to adopt a more hawkish stance, and instituted defense reforms that reflected a growing comfort with expanding the SDF's capabilities. A series of alarming provocations from North Korea and China's increased maritime assertiveness also played a role in reinforcing the sense that the U.S.-Japan alliance remained relevant and essential.

Author Contact Information

Emma Chanlett-Avery, Coordinator, Specialist in Asian Affairs ([email address scrubbed], [phone number scrubbed])
Caitlin Campbell, Analyst in Asian Affairs ([email address scrubbed], [phone number scrubbed])
Joshua A. Williams, Research Associate ([email address scrubbed], [phone number scrubbed])



The phrase "U.S.-Japan alliance" can describe a wide range of cooperative activities and programs, but this report focuses on the political and military partnership between the United States and Japan. For information and analysis on the broader relationship, see CRS Report RL33436, Japan-U.S. Relations: Issues for Congress, coordinated by Emma Chanlett-Avery.


U.S. Department of Defense, Indo-Pacific Strategy Report: Preparedness, Partnerships, and Promoting a Networked Region, June 1, 2019, p. 23.


Of the approximately 54,000 U.S. military personnel based in Japan, about 11,000 are afloat in nearby waters. Source: U.S. Forces Japan.


For example, Congress inserted in the FY2013 National Defense Authorization Act (H.R. 4310, P.L. 112-239) a resolution stating, among other items, that "the unilateral action of a third party will not affect the United States' acknowledgment of the administration of Japan over the Senkaku Islands," language that since 2012 has reappeared in a number of bills and resolutions concerning U.S. interests in the East China Sea. The implication of asserting that Japan administers the disputed islets, which China claims and calls the Diaoyu, is that the U.S.-Japan Treaty covers the islets. Subsequent legislation supporting Japan's claims in the East China Sea include §114 of S. 1635, the FY2016 Department of State Operations Authorization and Embassy Security Act, which the Senate passed by unanimous consent on April 28, 2016; §104 and of the Asia-Pacific Maritime Security Initiative Act of 2016 (S. 2865 in the Senate and H.R. 5890 in the House); and multiple provisions of S. 659, introduced in the 115th Congress, including sections that proposed sanctioning countries that recognize China's claim to the Senkakus.


U.S.-Japan Congressional Caucus, "About," at


"Top Senators Call U.S. Military Plans in Japan Unworkable, Unaffordable," Stars and Stripes, May 12, 2011.


For more on ARIA, see CRS In Focus IF11148, The Asia Reassurance Initiative Act (ARIA) of 2018, coordinated by Michael F. Martin.


The White House, "Joint Statement from President Donald J. Trump and Prime Minister Shinzo Abe," February 10, 2017,


Japan Ministry of Foreign Affairs, "Japan-U.S. Security Treaty," at


The White House, "Remarks by President Trump at APEC CEO Summit/Da Nang, Vietnam," November 10, 2017.


"Trump, Abe Friendship Remains on Par," CNN News, November 4, 2017.


Jesse Johnson, "More in Japan see U.S. as 'Major Threat,' While Cyberattacks and Climate Change Top Concerns, Survey Says," Japan Times, February 12, 2019, at; John Grady, "Panel: Trump's 'America First' Pledge Shocked Japan," USNI News, January 25, 2017, at


"U.S. Allies in Asia-Pacific Region Rattled After Mattis Quits," Reuters, December 21, 2018.


"READ: James Mattis' Resignation Letter," CNN Politics, December 21, 2018.


Ryo Sahashi, "The Indo-Pacific in Japan's Foreign Policy," Strategic Japan Working Papers, Center for Strategic and International Studies, 2019.


See CRS Report R42448, Pivot to the Pacific? The Obama Administration's "Rebalancing" Toward Asia, coordinated by Mark E. Manyin.


U.S. Department of Defense, Indo-Pacific Strategy Report: Preparedness, Partnerships, and Promoting a Networked Region, June 1, 2019.


U.S.-Japan Security Consultative Committee, "Joint Statement of the Security Consultative Committee," April 19, 2019, at


The White House, National Security Strategy of the United States of America, December 2017, pp. 2, 27.


U.S. Department of Defense, Summary of the 2018 National Defense Strategy of the United States of America: Sharpening the American Military's Competitive Edge, January 2018.


Japan Ministry of Defense, National Defense Program Guidelines for FY2019 and Beyond, December 18, 2018 (provisional English translation), p. 5, at


U.S.-Japan Security Consultative Committee, "Joint Statement of the Security Consultative Committee," April 19, 2019, at


Jeffrey Hornung and Kenneth McElwain, "Abe's Victory and Constitutional Revision," Foreign Affairs, October 31, 2017.


See, for example, Michael O'Hanlon, The Senkaku Paradox. Brookings Institution Press, April 30, 2019.


Sheila Smith, Japan Rearmed, Harvard University Press, 2019.


Jeffrey W. Hornung and Mike Mochizuki, "Japan: Still an Exceptional U.S. Ally," Washington Quarterly, Issue 39, No. 1 (Spring 2016), pp. 95-116.


Full text of the Constitution of Japan found at


Jeffrey W. Hornung, "With Little Fanfare, Japan Just Changed the Way It Uses Its Military," Foriegn Policy, May 3, 2019, at


Reiji Yoshida, "Abe's Route to Revising Article 9 Crosses Minefield of Legalese," Japan Times, March 12, 2018.


"Amending Japan's Pacifist Constitution," Institute for Security and Development Policy (Sweden), April 2018.


Steve Holland, Kiyoshi Takenaka, "Trump Says U.S. Committed to Japan Security, in Change from Campaign Rhetoric," Reuters, February 10, 2017, at; Phil Stewart, Nobuhiro Kubo, "Mattis Reaffirms U.S. Alliance with Japan 'For Years to Come,'" Reuters, February 3, 2017.


Stockholm International Peace Research Institute, "SIPRI Military Expenditure Database," at Access April 25, 2019.


Japan Ministry of Defense, "National Defense Program Guidelines for FY 2019 and beyond," December 18, 2018, at


Amanda Macias, "Trump vows to bolster the military by boosting the Pentagon's budget and reassessing foreign alliances," CNBC, February 5, 2019, at


"Testimony of USPACOM Commander, Adm. Harry B. Harris, Jr., in U.S. Congress, House Committee on Armed Services, The Military Posture and Security Challenges in the Indo-Asia-Pacific Region, hearings, 115th Cong., 2nd sess., February 14, 2018, H.A.S.C. No. 115-70 (Washington, DC: GPO, 2018).


Motoko Rich, "A Pacifist Japan Starts to Embrace the Military," New York Times, August 29, 2017; Paul Midford, Rethinking Japanese Public Opinion and Security: From Pacifism to Realism? (Stanford, CA: Stanford University Press, 2011).


Adam Liff and Ko Maeda, "Why Shinzo Abe Faces an Uphill Battle to Revise Japan's Constitution," Order From Chaos, Brookings Institution, December 15, 2018.


Kyodo, "Poll Shows 54% Oppose Revision of Japan's Pacifist Constitution Under Abe's Watch," April 11, 2019.


Council on Foreign Relations, "Constitutional Change in Japan," at


Sheila Smith, Japan Rearmed, Harvard University Press, 2019.


"Joint Statement of the Security Consultative Committee: A Stronger Alliance for a Dynamic Security Environment," April 27, 2015 and "Joint Statement of the Security Consultative Committee," April 19, 2019. ASEAN members include Indonesia, Thailand, Singapore, Malaysia, the Philippines, Vietnam, Brunei, Cambodia, Myanmar (Burma), and Laos.


"The Emerging Asia Power Web: The Rise of Bilateral Intra-Asian Security Ties," Center for a New American Security, June 2013,


Rare earth elements, a category of minerals that are essential components in many high-tech goods, are crucial inputs to many products manufactured in Japan. The export ban was particularly potent because China mines and exports more than 90% of the world's rare earth elements. Martin Fackler and Ian Johnson, "Arrest in Disputed Seas Riles China and Japan," New York Times, September 19, 2010, at; Keith Bradsher, "Amid Tension, China Blocks Vital Exports to Japan," New York Times, September 22, 2010, at


In April 2012, Tokyo governor Shintaro Ishihara announced that he intended to have the metropolitan government purchase three of the eight land features from their private Japanese owner. Ishihara, who is known for expressing nationalist views, called for demonstrating Japan's control over the islets by building installations on the island and raised nearly $20 million in private donations for the purchase. In September, the central government purchased the three islets for ¥2.05 billion (about $26 million at the then-prevailing exchange rate of ¥78:$1) to block Ishihara's move and reduce tension with China.


"Japan to Shoot Down Foreign Drones That Invade Its Airspace," Kyodo News Service, October 20, 2013.


Japanese Ministry of Defense; Open Source Enterprise, "China-Japan: Reported Air, Maritime Activity Near Senkaku Islands in 2018," February 12, 2019. JPW2019020625820498; Open Source Enterprise, "China-Japan Reported air, Maritime, Activity Near Senkaku Islands January to March 2019," April 25, 2019. JPW2019042518677959.


An ADIZ is a designated area of airspace over land or water within which a country requires the immediate and positive identification, location, and air traffic control of aircraft in the interest of the country's national security. While many countries have established one or more ADIZs in the interest of national security, no international agreement or consensus exists regarding the establishment of or the flight operations and air traffic procedures related to such airspace. ADIZs are located primarily over waters off coastal nations and often include large swaths of airspace beyond the boundaries of territorial lands and waters. CRS Report R43894, China's Air Defense Identification Zone (ADIZ), by Ian E. Rinehart and Bart Elias; Federal Aviation Administration, Pilot/Controller Glossary (P/CG), an addendum to the Aeronautical Information Manual, Order JO 7110.10, Flight Services, and Order JO 7110.65, Air Traffic Control, July 24, 2014.


Mark R. Cozad, Nathan Beauchamp-Mustafaga, "People's Liberation Army Air Force Operations over Water: Maintaining Relevance in China's Changing Security Environment," RAND Corporation, 2017, pp. 21-24; Michael Pilger, "ADIZ Update: Enforcement in the East China Sea, Prospects for the South China Sea, and Implications for the United States," U.S.-China Economic and Security Review Commission, March 2, 2016. In January 2019, a Chinese state media outlet reportedly released a video clip featuring a Chinese pilot engaging a foreign aircraft, with the pilot saying, "You have entered the Chinese ADIZ. Report your nationality ID and purpose of the flight." The report did not note how or whether the other aircraft responded. These kinds of reports are infrequent and often include limited information; it is unclear whether media reporting of these incidents is representative of the frequency and nature of engagements between aircraft in China's ADIZ. Teddy Ng, "Chinese Fighter Pilot Issues Warning to Foreign Aircraft in East China Sea Air Identification Zone," South China Morning Post, January 5, 2019, at


Atsuko Matsumoto, "Obama: Senkakus 'Within Scope' of U.S.-Japan Treaty," Yomiuri Shimbun, April 23, 2014.


Seth Cropsey, Jun Isomura, and James Conway, "U.S.-Japan Cooperation on Strategic Islands Defense," Hudson Institute, September 2018, pp. 15-17. For more information and analysis, see CRS Report R42761, The Senkakus (Diaoyu/Diaoyutai) Dispute: U.S. Treaty Obligations, by Mark E. Manyin.


Adam P. Liff, "China and the US Alliance System" China Quarterly, No. 233, March 2018, pp. 144-148.


U.S. Department of Defense, Military and Security Developments Involving the People's Republic of China 2019, May 2, 2019, pp. 44, 55, 62; Evan Heginbotham et al., "The U.S-China Military Scorecard: Forces, Geography, and the Evolving Balance of Power 1996-2017," RAND Corporation, 2015, pp. 56-57.


Japan Ministry of Defense, "Prime Minister Abe Visits China," October 26, 2018, at; Shutaro Sano, "Japan Buckles Up to Join China's Belt and Road," East Asia Forum, March 20, 2018, at


Jonathan D. Pollack, "Abe in Beijing: The Quiet Accommodation in China-Japan Relations," Brookings Institution, October 25, 2018, at; Duan Fengyuan et al., "Can China, Japan Maintain the Trend of Détente?" CGTN (China Global Television Network), August 12, 2018, at


The Japanese Government has asserted at least 17 were abducted, but some sources claim up to 900 individuals were abducted. See Headquarters for the Abduction Issue, Government of Japan, "Abductions of Japanese Citizens by North Korea: For Their Immediate Return!," October 2018, at


David Albright, "North Korean Miniaturization," 38North blog, US-Korea Institute at SAIS, February 22, 2013, at


AFP, "Japan's Defence Minister Says US-South Korea Military Drills 'Vital,'" June 13, 2018, at


Kyodo, "Abe Sends Ritual Tree Offering to War-Linked Yasakuni Shrine for Spring Festival," April 21, 2019, at


Kim Bo-eun, "Controversy Rises over GSOMIA amid Radar Spat," Korea Times, January 18, 2019, at; Yeo Jun-suk, "South Korea Refuses to Share Military Intelligence with Japan: Report," Korea Herald, November 19, 2017, at


"Australia and Japan to Strengthen Defence Ties on Shinzo Abe's Historic Darwin Visit," Financial Review, November 11, 2018.


"Japan's Death Penalty Hinders Defense Talks with Australia," Asahi Shimbun, March 25, 2019.


"Remarks By Prime Minister Abe to the Australian Parliament," July 8, 2014, Prime Minister and his Cabinet website.


Thomas S. Wilkins, "From Strategic Partnership to Strategic Alliance? Australia-Japan Security Ties and the Asia-Pacific," Asia Policy 20, National Bureau of Asia Research, July 2015.


Mina Pollmann, "US-Japan-Australia Security Cooperation: Beyond Containment," The Diplomat. April 21, 2015.


Ankit Panda, "A First: Leaders of US, Japan, India to Meet on 2018 G20 Sidelines for Trilateral," The Diplomat, November 28, 2018, at; Josh Rogin, "Inside the First Ever U.S.-Japan-India Trilateral Meeting," Foreign Policy, December 23, 2011, at


"Russia and Japan: No Closer to a Kuril Islands Breakthrough," The Diplomat, January 23, 2019.


"Ensuring no Future U.S. Military Presence on Disputed Isles is Key for Russia in Talks with Japan," Japan Times, November 29, 2018.


In the first half of FY2017, for example, the ASDF reports 287 scrambles in response to Chinese aircraft and 267 scrambles in response to Russian aircraft. See


U.S. Department of Defense, Indo-Pacific Strategy Report: Preparedness, Partnerships, and Promoting a Networked Region, June 1, 2019, p. 31; Japan Ministry of Foreign Affairs, "The Result of the Presidential Election in Taiwan (Statement of Foreign Minister Fumio Kishida)," January 16, 2016, at; Nikkei Asian Review, "Japan's Abe Calls Taiwan 'Important Partner,'" March 30, 2017, at


Joseph Yeh, "Japanese Foreign Minister Voices Support for Taiwan's WHA Bid," Focus Taiwan News Channel, May 8, 2019; "Japan Welcomes Taiwan's Bid to Joint Trade Pact," Channel News Asia, February 15, 2019.


Yasuto Tanaka, "Exclusive Interview: Taiwan's President Tsai Ing-wen Seeks Security Talks with Japanese Government," Japan Forward, March 3, 2019.


Testimony of Daniel R. Russel, then Assistant Secretary of State for East Asian and Pacific Affairs, in U.S. Congress, Senate Committee on Foreign Relations Subcommittee on East Asian and Pacific Affairs, Evaluating U.S. Policy on Taiwan on the 35th Anniversary of the Taiwan Relations Act, hearings, 113th Cong., 2nd sess., April 3, 2014.


Jeffrey Hornung, "Strong but Constrained Japan-Taiwan Ties," Brookings Op-ed, March 13, 2018.


Testimony of U.S. INDOPACOM Commander Philip S. Davidson, in U.S. Congress, Senate Armed Services Committee, United States Indo-Pacific Command and United States Forces Korea, hearings, 116th Cong., 1st sess., February 12, 2019.


The SDF deployed three CH-47 helicopters, three UH-1 helicopters, the amphibious transport vessel Osumi, helicopter carrier Ise, supply vessel Towada, two KC-767 supply aircraft, seven C-130 supply aircraft, and one U-4 aircraft. Source: Embassy of Japan in the United States, November 2013.


North Atlantic Treaty Organization, "Joint Political Declaration between Japan and the North Atlantic Treaty Organisation," April 12, 2013, at


North Atlantic Treaty Organization, "Partnership Interoperability Initiative," June 7, 2017, at


"Relations with Japan," North Atlantic Treaty Organization website news, September 12, 2018, at


"NATO and Japan Conduct Exercise in the Baltic Sea," North Atlantic Treaty Organization website news, August 27, 2018.


Monavar Khalaj et al., "Japan's PM Shinzo Abe Makes Diplomatic Push in Iran," Financial Times, June 12, 2019, at; Amir Vahdat et al., "Japan Premier Warns US, Iran 'Accidental Conflict' Possible," Stars and Stripes, June 12, 2019, at


For example, in response to the question "Would you be willing to withdraw U.S. forces from places like Japan and South Korea if they don't increase their contribution significantly?" Trump responded, "Yes, I would. I would not do so happily, but I would be willing to do it." "Transcript: Donald Trump Expounds on His Foreign Policy Views," New York Times, March 26, 2016; "Transcript: Donald Trump on NATO, Turkey's Coup Attempt and the World," New York Times, July 21, 2016. See also Hikotani Takako, "Trump's Gift to Japan," Foreign Affairs, September/October 2017 and "Trump Rips U.S. Defense of Japan as One-sided, Too Expensive," Japan Times, August 6, 2016.


"2004 Statistical Compendium on Allied Contributions to the Common Defense." See


"How Much Does Japan Pay to Host U.S. Forces? Depends on Who You Ask," Japan Times. January 31, 2017.

"Zainichi-mai-gun chūryū keihi , nippon futan wa 86 % bōei-shō shisan" 在日米軍駐留経費、日本負担は86% 防衛省試算 [Cost for the stationing of USFJ, Japanese Share is 86%, Ministry of Defense Calculations] 日本経済新聞 Nippon Keizai Shimbun, January 25, 2017,


Michael J. Lostumbo et al., "Host-Nation Support and U.S. Payments to Other Countries," in Overseas Basing of U.S. Military Forces: An Assessment of Relative Costs and Strategic Benefits, 131-66. RAND Corporation, 2013, at


Office of the Under Secretary of Defense, Comptroller, Operation and Maintenance Overview: Fiscal Year 2019 Budget Estimates, Washington, DC, March 2018, pp. 200-203; Office of the Under Secretary of Defense, Comptroller, Operation and Maintenance Overview: Fiscal Year 2017 Budget Estimates, Washington, DC, February 2016, pp. 225-228; Office of the Under Secretary of Defense, Comptroller, Operation and Maintenance Overview: Fiscal Year 2015 Budget Estimates, Washington, DC, March 2014, pp. 192-195.


Estimate based on an exchange rate of 110 JPY to 1 USD.


Japanese Ministry of Foreign Affairs, "U.S. Forces in Japan-Related Costs Borne by Japan (JFY2015),"


Figures provided by U.S. officials at the Office of the Secretary of Defense, January 2017.


Treaty of Mutual Cooperation and Security between Japan and the United States of America, 1960, at The 1960 Treaty replaced a 1952 bilateral Security Treaty.


The SCC released 13 joint statements between 2000 and 2017. The joint statements generally are issued at the conclusion of a 2+2 meeting, although joint statements have been released without the 2+2 convening. A record of joint statements is available at


Japan Ministry of Foreign Affairs, "Joint Statement of the Security Consultative Committee," August 17, 2017, at A Chinese Ministry of Foreign Affairs spokesperson responded to the SCC's reference to the South and East China Seas by saying, "As the US and Japan are not the directly concerned parties of the South China Sea issue, they ought to speak and act in a cautious manner and respect the efforts of regional countries to peacefully resolve the relevant disputes through consultation and negotiation, rather than the opposite. The Chinese side strongly urges the US and Japan to adopt a responsible attitude on the relevant issue, stop make erroneous remarks and do more things that are conducive to regional peace and stability." China's Ministry of Foreign Affairs, "Foreign Ministry Spokesperson Hua Chunying's Regular Press Conference on August 18, 2017," August 18, 2017, at


Japan Ministry of Foreign Affairs, "Joint Statement of the Security Consultative Committee," August 17, 2017, at


U.S. Department of State, "Joint Statement of the Security Consultative Committee," April 19, 2019, at This development brings the U.S.-Japan alliance in line with NATO doctrine on matters of cyber defense. NATO declared in 2014 that a cyber attack "could lead to the invocation of [NATO's] collective defense clause." Japan's constitutional constraints on the use of offensive force likely will uniquely shape a U.S.-Japan alliance response to a cyber attack. NATO Review Magazine, "NATO's Role in Cyberspace," February 12, 2019, at


U.S. Department of State, "U.S.-Japan Security Consultative Committee 2019 Fact Sheet," April 19, 2019, at


U.S. Department of State, "Joint Statement of the Security Consultative Committee," April 19, 2019, at; U.S. Department of State, "Remarks with Acting Secretary of Defense Patrick Shanahan, Japanese Foreign Minister Taro Kono, and Japanese Defense Minister Takeshi Awaya at a Joint Press Availability for the U.S.-Japan 2+2 Ministerial," April 19, 2019, at


U.S. Department of State, "Remarks with Acting Secretary of Defense Patrick Shanahan, Japanese Foreign Minister Taro Kono, and Japanese Defense Minister Takeshi Awaya at a Joint Press Availability for the U.S.-Japan 2+2 Ministerial," April 19, 2019, at


James L. Schoff, "Uncommon Alliance for the Common Good: The United States and Japan after the Cold War," Carnegie Endowment for International Peace, 2017, p. 30.


Jeffrey W. Horning, "Managing the U.S.-Japan Alliance: An Examination of Structural Linkages in the Security Relationship," Sasakawa USA, 2017, pp. 50-51.


Jeffrey W. Horning, "Managing the U.S.-Japan Alliance: An Examination of Structural Linkages in the Security Relationship," Sasakawa USA, 2017, pp. 50-52.


Center for Strategic and International Studies, "Asia-Pacific Rebalance 2025: Capabilities, Presence, and Partnerships," January 2016, p. 58.


Japan Ministry of Foreign Affairs, "United States-Japan Roadmap for Realignment Implementation," May 1, 2006,; U.S.-Japan Security Consultative Committee, "Joint Statement of the Security Consultative Committee," April 27, 2012.


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, pp. 285, 288.


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 285.


Tyler Hlavac, "Carrier Air Wing 5 Fighter Squadrons Moving to Iwakuni this Week," Stars and Stripes, March 28, 2018, at


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 285.


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 285.


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 300.


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 285.


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 285.


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 285.


Many of these assessed deficiencies are related to insufficient or nonexistent training facilities in locations to which Marines have been or are being relocated. Government Accountability Office, "Marine Corps Asia Pacific Realignment: DOD Should Resolve Capability Deficiencies and Infrastructure Risks and Revise Cost Estimates," Report to Congressional Committees, April 2017, pp. 17, 19-25.


Jim McNerny, Michael Green, Kiyoaki Aburaki, and Nicholas Szechenyi, "Partnership for Recovery and a Stronger Future; Standing with Japan after 3-11," Center for Strategic and International Studies, October 2011, at


Japan Times, "Japan Approves Plan to Send SDF Officers to Sinai, on First Non-U.N. Peacekeeping Mission," April 2, 2019, at


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 380.


Association of Southeast Asian Nations, "Overview of ASEAN-Japan Dialogue Relations," August 16, 2018.


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 349; Japan Ministry of Defense, "Vientiane Vision: Japan's Defense Cooperation Initiative with ASEAN."


Japan Ministry of Defense, Defense of Japan 2018, White paper, August 2018, p. 349.


"India Keeps Australia Out of the Malabar Exercise – Again," The Diplomat, May 8, 2018.


U.S. Department of State, "Australia-India-Japan-U.S. Consultations on the Indo-Pacific," November 12, 2017, at; U.S. Department of State, "U.S.-Australia-India-Japan Consultations," June 7, 2018, at; U.S. Department of State, "U.S.-Australia-India-Japan Consultations," November 15, 2018, at


Elizabeth Shim, "Report: Japan Increased Protection of U.S. Military Assets after 2016," UPI, March 29, 2019, at


Unlike the U.S. Coast Guard, which is considered an "Armed Force," the Japanese constitution states that the Japan Coast Guard does not take on responsibilities of an armed force or military organization. Lyle J. Morris, "Blunt Defenders of Sovereignty – The Rise of Coast Guards in East and Southeast Asia," Naval War College Review, vol. 70, no. 2 (Spring 2017), pp. 15-16.


Japan Coast Guard, "Mission of the JCG," at


Richard J. Samuels, "'New Fighting Power!' for Japan?" MIT Center for International Studies, September 2007.


Lyle J. Morris, "Crossing Interagency Lines: Enhancing Navy-Coast Guard Cooperation to Combat Gray Zone Conflicts of East Asia," Asia-Pacific Journal of Ocean Law and Policy, vol. 3 (2018), pp. 286-288.


U.S. Coast Guard, "U.S. Coast Guard Enforces North Korea Sanctions in the East China Sea," March 18, 2019, at


Walter T. Ham IV, "Japan Coast Guard Marks 150th Marine Aids to Navigation Anniversary," Coast Guard Compass, December 3, 2018, at; Prashanth Parameswaran, "ASEAN-Japan Coast Guard Cooperation in the Spotlight with Philippines Exercise," Diplomat, November 25, 2017, at


Bryan Clark and Jesse Sloman, Deploying Beyond Their Means: America's Navy and Marine Corps at a Tipping Point, Center for Strategic and Budgetary Assessments, November 18, 2015.


Michael Green, Kathleen Hicks, and Mark Cancian, et al., Asia-Pacific Rebalance 2025: Capabilities, Presence, and Partnerships, Center for Strategic and International Studies, January 2016, p. 203.


See CRS Report 92-744 F, Aircraft Carrier Forward Homeporting, October 2, 1992, by Ronald O'Rourke, and CRS Report 91-516 F, Aircraft Carrier Force Levels and Deployment Patterns: Issues and Options, June 28, 1991, by Ronald O'Rourke. See also CRS Report 92-803 F, Naval Forward Deployments and the Size of the Navy, November 13, 1992, by Ronald O'Rourke. These reports are available to congressional clients from the author upon request.


For more information and analysis, see CRS Report R43116, Ballistic Missile Defense in the Asia-Pacific Region: Cooperation and Opposition, by Ian E. Rinehart, Steven A. Hildreth, and Susan V. Lawrence.


U.S. Department of Defense, 2019 Missile Defense Review, January 17, 2019, p. 67.


Thomas Karako, "Shield of the Pacific: Japan as a Giant Aegis Destroyer," Center for Strategic and International Studies, May 23, 2018.


Japan Ministry of Defense, Defense of Japan 2018, White Paper, August 2018, p. 324.


Japan Ministry of Defense, Defense of Japan 2018, White Paper, August 2018, p. 324.


Japan Ministry of Defense, Defense of Japan 2018, White Paper, August 2018, p. 324.


Jim Garamone, "Trilateral Cooperation Needed to Combat North Korean Threat," DoD News, October 31, 2017, at


Testimony of Lt. Gen. Samuel A. Greaves, Director, U.S. Missile Defense Agency, in U.S. Congress, Senate Armed Services Subcommittee on Strategic Forces, Missile Defense Policies and Programs, hearings, 116th Cong., 2nd sess., April 3, 2019; Jim Garamone, "Trilateral Cooperation Needed to Combat North Korean Threat," DoD News, October 31, 2017, at


Brad Roberts, "Extended Deterrence and Strategic Stability in Northeast Asia," National Institute of Defense Studies (Japan), Visiting Scholar Paper Series, No. 1, August 9, 2013, p. 24.


Japan Ministry of Foreign Affairs, "The Release of the U.S. Nuclear Posture Review (NPR) (Statement by Foreign Minister Taro Kono)," February 3, 2018, at


For example, Trump stated, "And, would I rather have North Korea have [nuclear weapons] with Japan sitting there having them also? You may very well be better off if that's the case. In other words, where Japan is defending itself against North Korea, which is a real problem." "Transcript: Donald Trump Expounds on His Foreign Policy Views," New York Times, March 26, 2016.


See, for example, Robert Manning, "Trump's 'Sopranos' Worldview Would Undo Asian Alliances," New Atlanticist blog post, March 29, 2016.


Japan Ministry of Defense, National Defense Program Guidelines for FY2019 and Beyond, December 18, 2018, p. 8 (provisional translation); Sugio Takahashi, "Ballistic Missile Defense in Japan: Deterrence and Military Transformation," Institut Français des Relations Internationales, December 2012, pp. 20-22.


Ibid., p. 20.


With NATO Plus-Five status, a country may bid on certain DOD contracts; engage in certain research and development programs with DOD and the Department of State; receive certain DOD loan guarantees; receive preferential treatment for U.S. exports of excess defense articles; and participate in certain NATO-related training programs. The other NATO Plus-Five countries are Australia, Israel, New Zealand, and South Korea.


Stockholm International Peace Research Institute, "Importer/Exporter TIV Tables," accessed April 17, 2019, at SIPRI's methodology for calculating the value of arms transfers is available at


Emi Nobuhiro and Emi Urabe, "Japan Snubs Homegrown Weaponry to Buy From the U.S.," Bloomberg, July 10, 2018, at


Jane's All the World's Aircraft 2001-2002, Edited by Paul Jackson, p. 299.


Jon Grevatt, "Japan steps back from F-35 assembly," Jane's Defence Industry, January 20, 2019, at


Japan Ministry of Defense, "Speech by Minister of Defense Iwaya at Center for Strategic and International Studies (CSIS)," January 17, 2019, at


Based on CRS analysis of data on major arms sales by the Defense Security Cooperation Agency, available at


U.S. Department of State, "U.S. Security Cooperation With Japan," May 21, 2018, at


U.S. Department of Defense, "The Guidelines for Japan-U.S. Defense Cooperation," April 27, 2015.


Gabriel Dominguez, "SM-3 Block IIA successfully completes intercept test," Jane's Defence Weekly, October 29, 2018, at


Ministry of Foreign Affairs of Japan, "Japan's Policies on the Control of Arms Exports," at


Ministry of Foreign Affairs of Japan, "The Three Principles on Transfer of Defense Equipment and Technology," at


Japan Ministry of Defense, Defense of Japan 2018, White Paper, August 2018, pp. 426-428


Jonathan Soble, "Japan Consortium Misses Out on $38.5 Billion Australian Submarine Deal," The New York Times, April 26, 2016, at; The Mainichi, "Australia signs multi-billion dollar submarine deal with French firm," February 11, 2019, at


Mike Mochizuki and Michael O'Hanlon, "Refocusing the U.S.-Japan Alliance: It's Not Just About an Air Base," Brookings Op-ed, December 18, 2009.


For more information and analysis, see CRS Report R42645, The U.S. Military Presence in Okinawa and the Futenma Base Controversy, by Emma Chanlett-Avery and Ian E. Rinehart, and CRS In Focus IF10672, U.S. Military Presence on Okinawa and Realignment to Guam, by Emma Chanlett-Avery, Christopher T. Mann, and Joshua A. Williams.


"Okinawa Says New Base to Cost 10 Times What Tokyo Estimated," Asahi News, December 12, 2018 and Gavin McCormack, "The Henoko Base Project: Okinawa's Tamaki Government at the Brink," The Asia Pacific Journal, December 15, 2018.


Testimony of USPACOM Commander Harry B. Harris, in U.S. Congress, House Committee on Armed Services, The Military Posture and Security Challenges in the Indo-Asia-Pacific Region, hearings, 115th Cong., 2nd sess., February 14, 2018, H.A.S.C. No. 115-70 (Washington, DC: GPO, 2018).


See, for example, "Nye Suggests Rotating U.S. Forces in Japan Around SDF Bases," Jiji Wire Service, December 25, 2014.


Dennis C. Blair and James R. Kendall, "U.S. Bases in Okinawa: What Must Be Done, And Quickly," Sasakawa Peace Foundation Report, January 14, 2016.


Jeffrey W. Hornung, "Modeling a Stronger U.S.-Japan Alliance: Assessing U.S. Alliance Structures," Center for Strategic and International Studies, November 2015.


U.S. Department of State, "Remarks With Acting Secretary of Defense Patrick Shanahan, Japanese Foreign Minister Taro Kono, and Japanese Defense Minister Takeshi Iwaya at a Joint Press Availability for the U.S.-Japan 2+2 Ministerial," April 19, 2019, at; Sasakawa Peace Foundation USA, "Sixth Annual Sasakawa USA Security Forum Focused on New Security Challenges for the U.S.-Japan Alliance," April 30, 2019, at


Japan Ministry of Defense, "Medium Term Defense Program (FY 2019 - FY 2023)," December 18, 2018, at; Japan Ministry of Defense, "National Defense Program Guidelines for FY 2019 and beyond," December 18, 2018, at


Japan Ministry of Defense, Defense of Japan 2018,White Paper, August 2018, p. 218.


Japan Ministry of Defense, Defense of Japan 2018, White Paper, August 2018, p. 218.


Sheila A. Smith, Japan's New Politics and the U.S.-Japan Alliance, Council on Foreign Relations, July 2014; Christopher W. Hughes, "Japan's Strategic Trajectory and Collective Self-Defense: Essential Continuity or Radical Shift?" The Journal of Japanese Studies, 43:1, Winter 2017, 93-126.


Japan Ministry of Defense, Defense of Japan 2018, White Paper, August 2018, p. 218.


Japan Ministry of Defense, "National Defense Program Guidelines for FY 2015 and Beyond," December 10, 2014, at


CRS interview with senior official in the Japanese Cabinet Office, June 2016.


Japan Ministry of Defense, "Medium Term Defense Program (FY2019-FY2023)," December 18, 2019 (Provisional translation), pp. 3, 10, 12. See also Franz-Stefan Gady, "Japan to Convert Izumo-class into F-35-Carrying Aircraft Carrier," The Diplomat, December 12, 2018, at; Jenevieve Molenda, "Japan to Acquire Two New Long-range Missiles," CSIS Missile Threat, March 18, 2019, at; Monica Montgomery, "Japan Looks to Purchase Cruise Missiles," Arms Control Association, July/August 2018, at


Debates among Japanese defense professionals over the adoption of offensive strike capabilities have been ongoing for decades and accelerated in 2005 upon the public revelation that in 1994 the military had conducted a study on strikes against enemy missile bases. James L. Schoff and David Song, "Five Things to Know about Japan's Possible Acquisition of Strike Capability," Carnegie Endowment for International Peace, August 14, 2017, at


Sheila Smith, Japan Rearmed: The Politics of Military Power (Cambridge, MA: Harvard University Press, 2019), p. 125; Yuki Tatsumi, "Japan Eyes 'Counter-Attack' Capability Against North Korea Missile Threat," The Diplomat, March 31, 2017, at; Michael Bosack, "The LDP Weighs in on Japan's Defense Posture," Tokyo Review, March 29, 2018, at


"The Guidelines for U.S.-Japan Defense Cooperation," April 27, 2015.


Japan Ministry of Defense, Defense of Japan 2018, White Paper, August 2018, p. 264.


Japan Ministry of Defense, "National Defense Program Guidelines for FY 2019 and beyond," December 18, 2018, at


Japan Ministry of Defense, "Medium Term Defense Program (FY 2019 - FY 2023)," December 18, 2018, at


These calculations are based on an exchange rate of 110 JPY to 1 USD, which reflects average exchange rates over the past 2-3 years.


Japan Ministry of Defense, "National Defense Program Guidelines for FY 2019 and beyond," December 18, 2018, at


U.S.-Japan Security Consultative Committee, "Joint Statement of the Security Consultative Committee," April 19, 2019, at


John Wright, "Solving Japan's Joint Operations Problem," The Diplomat, January 31, 2018, at


Michael Green, Kathleen Hicks, and Mark Cancian, et al., Asia-Pacific Rebalance 2025: Capabilities, Presence, and Partnerships, Center for Strategic and International Studies, January 2016, p. 200.


Japan Ministry of Defense, "National Defense Program Guidelines for FY 2019 and Beyond," December 18, 2018, at


Saadia M. Pekkanen and Paul Kallender-Umezu, "In Defense of Japan: From the Market to the Military in Space Policy," (Stanford University Press, 2010).


Nobuaki Hashimoto, "Briefing Memo: Establishment of the Basic Space Law – Japan's Space Security Policy," The National Institute for Defense Studies News, July 2008 (No. 123), at


Paul Kallender-Umezu, "Japan Launches Spare IGS Radar Recon Satellite on H-2A," Spacenews, February 1, 2015, at


"Japan launches H-IIA rocket carrying intelligence-gathering satellite," The Japan Times, June 12, 2018,


"Japan Launches Satellite to Modernise Military Communications,", January 24, 2017,; "Results of the launch of Defense Communication Satellite-1(Kirameki 1) in association with the Program to Upgrade and Operate X-Band Satellite Communications Functions, etc.," SKY Perfect JSAT Corporation, April 6, 2018,


"Joint Statement: The First Meeting of the Japan-U.S. Comprehensive Dialogue on Space," March 11, 2013, at


"Space Situational Awareness, Services and Information, Agreement Between the United States of America and Japan," May 28, 2013, at


"Japan, US to Collaborate on Space Surveillance," The Mainichi, March 30, 2019, at


"U.S.-Japan Security Consultative Committee 2019 Fact Sheet," April 19, 2019, at


Paul Kallender and Christopher W. Hughes, 2017, "Japan's Emerging Trajectory as a 'Cyber Power': From Securitization to Militarization of Cyberspace," Journal of Strategic Studies, 40:1-2, 118-145.


NISC, "Japanese Government's Efforts to Address Information Security Issues," November 2008, at


Library of Congress Global Legal Monitor, "Japan: Cybersecurity Basic Act Adopted," December 10, 2018, at

Library of Congress Global Legal Monitor, "Japan: Basic Act on Cybersecurity Amended," December 26, 2018, at; Paul Kallender and Christopher W. Hughes, 2017, "Japan's Emerging Trajectory as a 'Cyber Power': From Securitization to Militarization of Cyberspace," Journal of Strategic Studies, 40:1-2, 118-145.


NISC, "Summary of the Japan's Cybersecurity Strategy (July 27, 2018 Cabinet Decision)," at


Japan Ministry of Defense, Medium Term Defense Program (FY2019-FY2023), December 18, 2018, provisional translation, p. 3.


Taketsugu Sato, "Japan Faces Legal Snags in Building Defense against Cyber-attacks," The Asahi Shimbun, December 2, 2018, at


Paul Kallender and Christopher W. Hughes, 2017, "Japan's Emerging Trajectory as a 'Cyber Power': From Securitization to Militarization of Cyberspace," Journal of Strategic Studies, 40:1-2, 118-145.


U.S. Department of State, "Joint Statement of the Japan-U.S. Cyber Dialogue," July 24, 2017, at


"Joint Statement of the Security Consultative Committee," April 19, 2019, at; Daniel Hurst, "Japan, US Beef up Their Cyber Alliance," The Diplomat, April 26, 2019, at


Aki Nakai, "Japan Gears up for Electronic Warfare," The Diplomat, September 5, 2018, at a


U.S. Department of Defense, "DOD Dictionary of Military and Associated Terms," April 2019, at


Aki Nakai, "Japan Gears up for Electronic Warfare," The Diplomat, September 5, 2018, at


Scott W. Harold, Koichiro Bansho, Jeffrey W. Hornung, Koichi Isobe, Richard L. Simcock II, "U.S.-Japan Alliance Conference: Meeting the Challenge of Amphibious Operations," Rand Corporation, 2018, at


Gidget Fuentes, "U.S. Marines Teach Japanese Forces How to Fight From the Sea in Expanded Iron Fist Exercise," USNI News, January 25, 2016.


"Japanese Self-Defense Forces launch 1st amphibious fighting unit," Kyodo News, April 7, 2018, at


Justin McCurry, "Japan to get First Aircraft Carrier since Second World War amid China Concerns," The Guardian, November 28, 2018, at


"The United States and Japan: Advancing Toward a Mature Partnership," Institute for National Strategic Studies, National Defense University, INSS Special Report, October 11, 2000.


The SDF operated under restrictions in Iraq: no combat unless fired upon and no offensive operations. Protection was provided by Dutch and Australian forces.