Armed Conflict in Syria: Overview and U.S. Response

October 13, 2017 (RL33487)
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The Syrian civil war, now in its seventh year, continues to present new challenges for U.S. policymakers. Following a deadly chemical weapons attack in Syria on April 4, 2017, and subsequent U.S. defensive strikes against Syrian military infrastructure and pro-Syrian regime forces, several Members of Congress have called on the President to consult with Congress about Syria strategy. Some Members have questioned the President's authority to launch strikes against Syria in the absence of specific prior authorization from Congress. In the past, some in Congress have expressed concern about the international and domestic authorizations for such strikes in Syria, their potential unintended consequences, and the possibility of undesirable or unavoidable escalation of the Syria conflict.

Since taking office in January 2017, President Trump has stated his intention to "destroy" the Syria- and Iraq-based insurgent terrorist group known as the Islamic State (IS, also known as ISIL, ISIS, or the Arabic acronym Da'esh), and the President has ordered actions to "accelerate" U.S. military efforts against the group in both Syria and Iraq. In late March, senior U.S. officials signaled that the United States would prioritize the fight against the Islamic State and said that Syrian President Bashar al Asad's future would be determined by the Syrian people. Senior members of the Trump Administration have spoken critically of the Syrian president's leadership but call for de-escalation of the underlying conflict and a negotiated settlement, rather than seeking to compel Syrian president Asad's departure from power.

Since late 2015, Syrian president Asad and his government have leveraged military, financial, and diplomatic support from Russia and Iran to improve and consolidate the Syrian government's position relative to the range of antigovernment insurgents arrayed against them. These insurgents include members of the Islamic State, Islamist and secular fighters, and Al Qaeda-linked networks in Syria. While Islamic State forces have lost territory to the Syrian government, to Turkey-backed Syrian opposition groups and to U.S.-backed Syrian Kurdish and Arab fighters since early 2016, they remain capable and dangerous. The IS "capital" at the Syrian provincial capital of Raqqah has been isolated and is being liberated, but large areas of eastern Syria remain under the group's control. The presence and activities of Russian military forces and Iranian personnel in Syria create complications for U.S. officials and military planners, and raise the prospect of inadvertent confrontation inside Syria with possible regional or global implications.

Since March 2011, the conflict has driven nearly 5.2 million Syrians into neighboring countries as refugees (out of a total prewar population of more than 22 million). More than 6.3 million other Syrians are internally displaced and are among more than 13.5 million Syrians in need of humanitarian assistance. The United States is the largest donor of humanitarian assistance to the Syria crisis (which includes assistance to neighboring countries hosting Syrian refugees), and since FY2012 has allocated nearly $7.4 billion to meet Syria-related humanitarian needs. In addition, the United States has allocated more than $500 million to date for bilateral assistance programs in Syria, including the provision of nonlethal equipment to select opposition groups. President Trump has requested $191.5 million in FY2018 funding for such assistance and $500 million in FY2018 defense funds to train and equip anti-IS forces in Syria.

U.S. officials and Members of Congress continue to debate how best to pursue U.S. regional security and counterterrorism goals in Syria without inadvertently strengthening U.S. adversaries or alienating U.S. partners. The Trump Administration and Members of the 115th Congress—like their predecessors—face challenges inherent to the simultaneous pursuit of U.S. nonproliferation, counterterrorism, civilian protection, and stabilization goals in Syria's evolving conflict.

Armed Conflict in Syria: Overview and U.S. Response


After six years of conflict, the challenges posed to U.S. national security by the situation in Syria have multiplied and evolved. Initial unrest and the Syrian government's violent response fueled U.S. concerns about Syria's stability and civilian protection in the midst of the 2011 "Arab Spring." The country's descent into brutal war created a multifaceted regional crisis, marked by the mass displacement of civilians, the emergence and empowerment of violent armed Islamist extremist groups, gross human rights abuses and war crimes, the use of chemical weapons, the proliferation of arms, and the covert and overt intervention of outside actors. Over time, U.S. policymakers have appeared to feel both compelled to respond to these interlocking crises and cautious in considering potentially risky options for doing so, such as the commitment of military forces or the provision of lethal assistance to combatants. The Obama Administration supported various partner forces in Syria, while calling for Asad's ouster through a negotiated transition.

Russia's forceful entrance into the conflict in 2015 bolstered flagging Syrian government forces, but has yet to enable President Bashar al Asad to reassert control over all of Syria. Government forces and their foreign allies (chiefly Russia, Iran, Lebanese Hezbollah, and Iraqi Shia militia groups) have gained at the expense of their various insurgent adversaries since late 2015, but armed opposition groups continue to control territory and durable political and military solutions remain elusive. Progress has been made by various parties in reducing the amount of territory held by the Islamic State, but competition and discord among local, regional, and extraregional actors continues to create complications for U.S. officials. As of 2017, principal U.S. concerns focus on combatting the Islamic State (IS, also known as ISIS/ISIL or by the Arabic acronym Da'esh) and other Syria-based extremists, while seeking a resolution to the underlying conflict.

In Congress, Members have weighed the relative risks and rewards of various proposed courses of action against the Islamic State and the Asad government while conducting oversight of U.S. assistance programs and military operations. To date, the United States has directed nearly $7.4 billion toward Syria-related humanitarian assistance, and Congress has appropriated billions more to support security and stabilization initiatives in Syria and in neighboring countries. The Defense Department has not disaggregated the costs of military operations in Syria from the overall cost of Operation Inherent Resolve (OIR), which has reached over $14.3 billion. Congress has approved the use of more than $1.3 billion to train and equip vetted Syrians as part of a specially authorized program in place since late 2014. Congress also has debated proposals to authorize or restrict the use of military force against the Islamic State and in response to Syrian government chemical weapons attacks, but has not enacted any Syria-specific force authorizations.

An April 2017 chemical weapons attack in Syria, resulting U.S. missile strikes, and defensive strikes on Syrian government and allied forces have rekindled debates in Congress about Syria policy, and these debates may intensify as the Trump Administration considers its options and further articulates its goals and strategy. Operations against the Islamic State are focused on the isolation and recapture of the city of Raqqah. After Raqqah, U.S. military officials and local partners may move against IS strongholds in the eastern Euphrates River valley, including areas adjacent to the Iraqi border. The 115th Congress is considering FY2018 appropriations and authorization legislation related to Syria, and may engage in renewed debate about overall U.S. strategy while considering the Trump Administration's FY2018 funding requests.

Immediate debates and developments notwithstanding, the degree of devastation and displacement already wrought by the conflict in Syria is overwhelming and may take Syrians and their neighbors decades to overcome. This context and the ongoing intersection in Syria of multiple U.S. national security interests suggest that Congress may face tough choices about U.S. Syria policy and related U.S. relief and security assistance programs for years to come.

Figure 1. Syria: Areas of Influence

Source: CRS using area of influence data from IHS Conflict Monitor, last revised September 26, 2017. All areas of influence approximate and subject to change. Other sources include U.N. OCHA, Esri, and social media reports.

Note: U.S. forces are reportedly operating in the vicinity of Ayn Issa and other areas of north central Syria in support of Syrian Democratic Forces (SDF) operations to isolate and recapture Raqqah.

Issues for Congress and Select Pending Legislation

Key issues under consideration in Congress relative to Syria include the following:

These issues are discussed in more detail below (see "U.S. Policy and Assistance").

Presidential Authority to Strike Syria Under U.S. Law1

As noted above, a series of U.S. strikes on targets in Syria during early 2017 reinvigorated debate in Congress over U.S. policy in Syria and the authorization for the use of military force there. In an April 8, 2017, letter to Congress, President Trump stated that he had acted "pursuant to my constitutional authority to conduct foreign relations and as Commander in Chief and Chief Executive" in ordering the April 6, 2017, U.S. missile strikes on Al Shayrat airbase in Syria in response to a chemical weapons attack on Khan Sheikhoun. In the letter, President Trump says that he "acted in the vital national security and foreign policy interests of the United States," and that, "the United States will take additional action, as necessary and appropriate, to further its important national interests." On April 6, the President said he ordered the strikes to protect the "vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons." The April 8 letter expands upon this explanation.2

In the past, Presidents have justified the use of military force by relying on presidential powers they assert are inherent under Article II Commander in Chief and Chief Executive authority. The executive branch has claimed that a President may use military force to defend U.S. national security interests (even when an immediate threat to the United States and its Armed Forces is not necessarily apparent) and to promote U.S. foreign policy.

In 2017, the U.S. military has used force against the Syrian government and their allies on limited occasions for force protection purposes, including for the protection of U.S. partner forces. In an August 2017 letter to Senate Foreign Relations Committee Chairman Senator Bob Corker, the State Department asserted that "the 2001 AUMF also provides authority to use force to defend U.S., Coalition and partner forces engaged in the campaign to defeat ISIS to the extent such use of force is a necessary and appropriate measure in support of counter-ISIS operations." The letter states

The strikes taken by the United States in May and June 2017 against the Syrian Government and pro-Syrian-Government forces were limited and lawful measures to counter immediate threats to U.S. or partner forces engaged in that campaign. The United States does not seek to fight the Syrian Government or pro-Syrian-Government forces However, the United States will not hesitate to use necessary and proportionate force to defend U.S., Coalition, or partner forces engaged in the campaign against ISIS.

Congress has debated Syria-specific and Islamic State-focused authorization for military force proposals intermittently in recent years.

In 2013, the Senate Foreign Relations Committee considered and reported a proposed authorization for the use of military force following a chemical weapons attack in the suburbs of Damascus, Syria (S.J.Res. 21). The Senate did not consider the measure further. Since U.S. military action against the Islamic State began in June 2014, starting in Iraq and then spreading to Syria, Congress also has debated the need for enactment of a new IS-specific authorization for use of military force. President Obama asserted that the campaign against the Islamic State in Iraq and Syria was authorized by both the Authorization for Use of Military Force (2001 AUMF; P.L. 107-40; claiming that the Islamic State was a successor organization of Al Qaeda and that elements of Al Qaeda were present in Syria) and Authorization for Use of Military Force Against Iraq Resolution of 2002 (2002 AUMF; P.L. 107-243; claiming authority to defend Iraq from the Islamic State threat).

Select Proposed Syria-Related Legislation

H.R. 2810/S. 1519, National Defense Authorization Act for FY2018. The House engrossed version of the bill (H.R. 2810) would endorse limits and terms for the use of funds for the transfer of man-portable air defense systems (MANPADs) to the vetted Syrian opposition, preserve oversight reporting on the Syria train and equip program, and require reporting on (1) potential Syria-related agreements with Russia, (2) U.S. strategy in Syria, (3) the implications of the Syria humanitarian crisis for U.S. policy in the region, and (4) the deployment of U.S. combat forces to Syria through FY2020. The Senate version does not contain these provisions and would set terms and limitations for the use of Syria train and equip program monies for construction projects. Neither bill would extend the underlying authority for the train and equip program, which is currently authorized through December 31, 2018.

S.Res. 116, Condemning the Asad regime for its continued use of chemical weapons against the Syrian people. Following the April 4, 2017, chemical weapons attack in Syria, several members of the Senate Foreign Relations Committee submitted a proposed resolution that, inter alia, would condemn Asad and Russia and call on the United Nations Security Council to take immediate, decisive action in response. The proposed resolution "reiterates that Bashar al-Assad has lost legitimacy as Syria's leader" and "insists that Bashar al-Assad must be held accountable for his war crimes and crimes against humanity."

H.R. 1923. Introduced April 5, 2017: would prohibit the President from using members of the Armed Forces "to carry out offensive combat operations in Syria unless Congress has enacted a specific authorization for such use of members of the Armed Forces."

Caesar Syria Civilian Protection Act. H.R. 1677, introduced by Representatives Royce and Engel (and others) on April 6, 2017: was referred to the Committees on Foreign Affairs, Financial Services, and the Judiciary. The bill updates and amends legislation (H.R. 5732) passed by the House in the 114th Congress, incorporating provisions from other proposed legislation and appearing to address some concerns expressed by various Syria policy stakeholders. On May 17, it passed the House and was referred to the Senate Committee on Foreign Relations.

As amended, H.R. 1677 would state that "It is the policy of the United States that all diplomatic and coercive economic means should be utilized to compel the government of Bashar al-Assad to immediately halt the wholesale slaughter of the Syrian people and to support an immediate transition to a democratic government in Syria that respects the rule of law, human rights, and peaceful coexistence with its neighbors." The bill would authorize the imposition of certain sanctions by the President and amend current law to require the President to impose other sanctions on individuals he designates as eligible. The bill would require the President to submit an updated report on individuals alleged to be responsible for "serious human rights abuses" in Syria, which the bill would amend current law to define. In defining "serious human rights abuses" and requiring the Administration to report on the responsibility of dozens of named individuals for such abuses, the bill appears to create a dynamic that would make it more difficult for the executive branch to decline to designate Syrian individuals for human rights-based sanctions.

The bill would expand the potential scope of existing U.S. sanctions on Syria by making eligible for sanctions parties engaged in certain transactions with or the provision of support to the government of Syria. Current executive orders impose such sanctions, in some cases. The sanctions authorized in the bill could be imposed on individuals determined by the President to have met designated criteria because of knowing engagement in actions "on or after" the date of enactment. The sanctions would thus be prospective rather than retrospective. The sanctions authorized could be imposed on U.S. nationals and non-nationals. A large number of individuals are already subject to U.S. Syria-related sanctions, and in some cases individuals may already be subject to U.S. sanctions for engaging in transactions with sanctioned individuals, including entities in Russia and Iran that provide military support to the Syrian government.

The bill would require within 90 days a report that assesses the potential effectiveness, risks, and operational requirements of the establishment and maintenance of a no-fly zone over part or all of Syria and the establishment of one or more safe zones in Syria for internally displaced persons or for the facilitation of humanitarian assistance. It would also codify authorization for certain services in support of nongovernmental organizations' activities in Syria.

The bill includes a national security waiver and negotiation or transition scenario-specific waiver authorities for the President. Its provisions would expire after December 31, 2021.

Preventing Destabilization of Iraq and Syria Act. In January 2017, Senators Rubio and Casey introduced S. 138, known as the Preventing Destabilization of Iraq and Syria Act of 2017. They had previously introduced the bill in December 2016 as S. 3536 (114th Congress), known as the Preventing Destabilization of Iraq and Syria Act of 2016. The bill incorporated many aspects of H.R. 5732 (114th Congress), including the requirement for the imposition of sanctions on the Central Bank of Syria as well as on foreign individuals that provide support for the Syrian government or for the maintenance or expansion of natural gas and petroleum production in Syria. In addition, it would have required the imposition of sanctions on Syrians complicit in the blocking of humanitarian aid. The bill also would have authorized the President to provide enhanced support for humanitarian activities in Syria, including the provision of food, shelter, water, health care, and medical supplies. It would have prohibited the President from imposing sanctions on a foreign financial institution for engaging in a transaction with the Central Bank of Syria for the sale of food, medicine, medical devices, donations intended to relieve human suffering, or nonlethal aid to the people of Syria. It further would have prohibited the President from imposing sanctions on internationally recognized humanitarian organizations for engaging in financial transactions related to the provision of humanitarian assistance, or for having incidental contact (in the course of providing humanitarian aid) with individuals under the control of foreign persons subject to sanctions under the act.

Stop Arming Terrorists Act. In January 2017, Representative Tulsi Gabbard introduced H.R. 608, known as the Stop Arming Terrorists Act. The bill would prohibit funds made available to any federal department or agency from being used to provide covered assistance to Al Qaeda and the Islamic State, or to any individual or group that is affiliated with, associated with, or cooperating with adherents of these groups. It would also prohibit direct or indirect covered assistance to countries that have provided assistance to Al Qaeda or the Islamic State, or to any individuals or groups affiliated with, associated with, or cooperating with adherents of these groups. Covered assistance is defined as defense articles, services, training, logistical support, or any other military assistance. It also includes intelligence sharing and cash assistance. The Director of National Intelligence (DNI) would make the initial determination of which groups have an affiliation or association with Al Qaeda and the Islamic State, and which countries provide assistance to those groups. In March 2017, Senator Rand Paul introduced the bill in the Senate as S. 532.

Conflict Synopsis

2011: Protests Emerge. In March 2011, protests broke out in the southern province of Dar'a. The unrest was sparked by the arrest of a group of school children, but reflected long-standing political and socioeconomic grievances. Largely peaceful protesters called for political and economic reforms rather than the removal of the Asad government. At the same time, a small armed element was also present within some of the protests. As security forces responded with mass arrests and occasionally opened fire on demonstrators, protests became larger and spread to other towns and provinces.

The opposition movement eventually coalesced into two umbrella groups—one political, one armed—and both based primarily in exile. Political groups merged to form the Syrian National Council (SNC), although members struggled to establish trust and develop shared goals. A small number of junior military defectors formed the Free Syrian Army (FSA), which claimed leadership over the armed opposition but whose authority was generally unrecognized by local armed groups. Ongoing violence, primarily but not exclusively on the part of the Syrian government, prompted President Obama in August 2011 to call for Syrian President Asad to step aside. Meanwhile Al Qaeda's affiliate in Iraq tasked some of its members to commence operations in Syria under the banner of a new group known as Jabhat al Nusra (aka the Nusra Front). In December 2011, the first Nusra Front suicide attacks hit government buildings in downtown Damascus.

2012: Insurgency. In 2012, the conflict became increasingly violent, as the government began to use artillery and fixed wing aircraft against opposition targets. Extremist attacks became more frequent—between November 2011 and December 2012, the Nusra Front claimed responsibility for nearly 600 attacks in Syria, ranging from more than 40 suicide attacks to small arms and improvised explosive device operations.3 In February 2012, the United States closed its embassy in Damascus, citing security concerns. Local armed groups began to seize pockets of territory around the country, primarily in rural areas. A July bombing in downtown Damascus killed several senior regime officials, including the then-Minister of Defense. Concerns about regime tactics became more acute, and President Obama in August declared that

We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized.... We have communicated in no uncertain terms with every player in the region that that's a red line for us and that there would be enormous consequences if we start seeing movement on the chemical weapons front or the use of chemical weapons.4

The international community also increased efforts to seek a negotiated solution to the conflict. In June, the United States and Russia signed the Geneva Communiqué, which called for the establishment of a transitional governing body with full executive powers.5 The document, which became the basis of future negotiations between the government and the opposition, did not clarify the role of Asad in any future government. Meanwhile, Syria's political opposition remained divided and in flux. In November, the SNC became part of a larger umbrella group known as the National Coalition of Syrian Revolutionary and Opposition Forces (aka the Syrian Opposition Coalition, SOC), a move which some described as an effort to dilute the influence of Islamist members.

2013: Proxy War and Chemical Weapons. In March 2013, rebels seized the city of Raqqah, which became the first provincial capital to fall out of government control. A series of other opposition victories in the area led the government to effectively concede control of Syria's rural northeast to the opposition. At the same time, the Asad government received military and intelligence support from Iran and Lebanese Hezbollah, as well as political backing from Russia. In turn, the United States, Turkey, and some European and Arab Gulf states increased their support to the Syrian opposition—each prioritizing their own interests and at times working at cross purposes.

In April, the United Kingdom and France reported to the United Nations that there was evidence that the Syrian government had used chemical weapons (CW) on multiple occasions since December 2012.6 In August, the United States attributed a large-scale CW attack on the Damascus suburb of Ghouta to the Syrian government.7 President Obama requested congressional approval of a limited authorization for the use of military force to respond.8 The following month, Russia negotiated an agreement for the Syrian government to dispose of its CW stockpiles and destroy associated facilities in exchange for staving off a U.S. military response.

2014: Caliphate and Operation Inherent Resolve (OIR). In February 2014, Al Qaeda formally disavowed the Islamic State because of the group's interference in Syria and its demands that the Nusra Front recognize IS leadership. After the Nusra Front and other opposition groups forced IS fighters from some areas of northwestern Syria, IS fighters seized vast stretches of territory in central and northeast Syria from local armed groups and in June declared the establishment of a caliphate spanning areas of both Syria and Iraq. Thousands of foreign fighters traveled to Syria and Iraq to join the Islamic State.

In August, the United States began air strikes in neighboring Iraq to stop the group's territorial advance and reduce the threat to U.S. personnel in Iraq. U.S. forces also airdropped humanitarian supplies to members of Iraq's Yazidi religious minority group trapped on Mount Sinjar. In September, the United States expanded air strikes to Syria, with the goal of preventing the Islamic State from using Syria as a base for its operations in Iraq. A subsequent air campaign to lift the IS siege on the Syrian Kurdish town of Kobane brought the United States into partnership with the Kurdish People's Protection Units (YPG), which U.S. officials have come to view as among the United States' most effective partners in the anti-IS campaign. In September 2014, Congress authorized the Administration to begin a train and equip program for select Syrian forces.9

2015: Train & Equip Begins, Russia Enters the Fray. In 2015, the Syrian government faced a number of additional territorial losses. Opposition forces captured the provincial capital of Idlib in northwestern Syria and surrounding areas with the support of Al Qaeda-linked fighters. Islamic State fighters seized territory in central Homs province, and Kurdish fighters expanded their control over areas along the Turkish border. In May, the United States began training the first batch of recruits for the Syria Train and Equip Program. The program was designed to build a local force capable of fighting the Islamic State, protecting opposition-held areas, and "promoting the conditions for a negotiated settlement to end the conflict in Syria."

Over the summer of 2015, Russia began a gradual buildup of Russian personnel, combat aircraft, and military equipment inside Syria, and began air strikes in September. The following month, the United States and Russia signed a memorandum of understanding to establish a safety-of-flight protocol for aircraft operating in the same airspace. Also in October, challenges in implementation led the Administration to modify the Syria Train and Equip program to focus on equipping existing units commanded by vetted leaders. Kurdish YPG forces that had received U.S. support in operations at Kobane merged with a small number of non-Kurdish groups to form the Syrian Democratic Forces (SDF), which began to receive U.S. support.

2016: Failed Cessation of Hostilities, Regime Retakes Aleppo. In 2016, the United States sought to step up diplomatic cooperation with Russia to achieve a reduction in violence. The two countries twice attempted to implement a joint diplomatic initiative for a cessation of hostilities (CoH) between progovernment and opposition forces, yet both initiatives were widely considered unsuccessful. In contrast, the U.S.-led campaign against the Islamic State retook significant territory from the group, severing much of the group's access to the Turkish border—a key supply and foreign fighter transit route. However, the heavy participation of Syrian Kurdish fighters in counter-IS operations triggered Turkish opposition, and in August Turkish forces crossed the Syrian border into the town of Jarabulus, in an operation described by Turkish officials as aimed at neutralizing threats posed by both the Islamic State and Kurdish fighters. Meanwhile, Syrian and Russian forces—backed by Hezbollah, foreign Shia militias, and Iranian forces—increased the intensity of attacks on rebel-held eastern Aleppo, resulting in thousands of deaths. In December 2016, the Syrian government recaptured eastern Aleppo from opposition forces, and Russia and Turkey reached agreement on a proposed cease-fire to be followed by negotiations (see "The Astana Process" below).

2017: U.S. Strikes Syrian Forces, Battle for Raqqah Begins. On April 4, Syrian aircraft operating in rebel-held Idlib province conducted several airstrikes using what U.S. officials assessed to be a chemical nerve agent.10 The strikes killed roughly 80 to 100 people in the town of Khan Sheikhoun (see map, Figure 1). On April 6, the United States fired 59 Tomahawk missiles at Al Shayrat airfield in Homs province, from which U.S. intelligence sources had concluded the Khan Sheikhoun attack was launched. A Defense Department assessment stated that the U.S. strikes resulted in the damage or destruction of fuel and ammunition sites, air defense capabilities, and about 20 Syrian aircraft.11 In a series of incidents in May and June, U.S. forces carried out defensive strikes against Syrian government and allied forces deemed to be threatening U.S. forces and U.S. partners in Syria (see "Syria-Iraq-Jordan Tri-border Area" below).

In June 2017, SDF forces announced the beginning of operations to retake the city of Raqqah, the self-declared capital of the Islamic State. SDF operations in Raqqah province to isolate the city had been ongoing since November 2016. In July, the United States, Russia, and Jordan finalized an agreement for a ceasefire in southwestern Syria to facilitate the delivery of humanitarian aid.

Russia's Military Intervention

Russian military involvement in Syria dates back to the 1950s. Soviet and Russian Federation naval forces have accessed a facility at the Syrian port of Tartus since the early 1970s, using it as a logistical hub to enable longer Mediterranean operations. Syria eventually became the largest Middle East recipient of Russian equipment and training. While Russian personnel have since been based in Syria to maintain Russia military equipment and train Syrians, their numbers have fluctuated over time.

With the onset of unrest in 2011, Russia provided sustained political, economic, and military support to the Syrian government. Russian diplomats blocked action in the U.N. Security Council that would have increased pressure on the Asad regime for its conduct. In 2012, Russia began printing Syrian banknotes after European sanctions prevented Syria's currency from being printed in Austria. After the chemical attacks outside Damascus in 2013, Russia negotiated an agreement whereby the Syrian government relinquished its chemical weapons, avoiding proposed U.S. military strikes. Throughout the conflict, Russia has continued to resupply Syrian military forces, although Russian officials have stated that they are merely fulfilling existing bilateral contracts.

Over the summer of 2015, Russia began a gradual buildup of personnel, combat aircraft, and military equipment inside Syria. In September of that year, Russian forces began air strikes inside Syria, initially focused on opposition targets—including some groups reportedly backed by the United States.12 In 2016, Russia expanded its targeting to include Islamic State forces, although it continued to occasionally target U.S.-backed rebel groups.13

The series of losses suffered by Syrian government forces in 2015 may have contributed to Russia's decision to enter the conflict directly when it did. Russian concerns about U.S. and other third-party security assistance to Syrian opposition groups, and the potential for broader U.S.-led coalition military operations in Syria, also may have been motivating factors. Russia remains an outspoken critic of what it describes as unwarranted external interference aimed at regime change in Syria and elsewhere.

To date, air strikes have constituted Russia's primary military effort in Syria. These strikes have enabled pro-Asad forces to reverse some opposition gains, particularly around Aleppo in 2016. Russia's introduction of advanced air defense systems in Syria (reportedly including the S-300 and S-400) constrains the ability of other aircraft to operate freely in the area. At the same time, Russia has pushed for cooperation between U.S. and Russian military forces in Syria against terrorist groups—which in Russia's view includes any group fighting the Asad government.

Russia also has a limited number of ground forces deployed in Syria. In September 2017, a Russian general was killed by IS artillery fire in Syria's eastern Deir ez Zor province. Russia's chief of general staff stated that the deceased general had been seconded to the Syrian military and served as commander of Syria's Fifth Corps—a volunteer force established in 2016.14

Russia has agreements to maintain a long-term presence at both the Tartus naval facility and the Hmeimim airbase in Latakia province. In July 2017, President Putin signed a law ratifying a deal struck with the Syrian government in January, allowing Russia to keep forces at the Hmeimim airbase for the next 49 years, with the option of extending that arrangement for subsequent 25 year periods.15

De-confliction with Russian Forces

In late 2015, the United States established air safety protocols with Russia to de-conflict air operations over Syria. In 2017, U.S. and Russian ground forces in Syria began to operate in close proximity to one another as part of operations to defeat the Islamic State, requiring additional de-confliction measures. Referencing U.S. de-confliction with Russian forces in areas under IS control, a U.S. military spokesperson stated:'s difficult to link up with someone while in contact with the enemy, and especially in the dark. So it gets even tougher when you have a force that may be something other than friendlynot necessarily an adversary, but something other than friendlyand you don't have great communications with them and you don't have an agreed-upon plan. Well, thenand then you add the enemy there, and it becomes fraught with friction. So we knew we had to have this de-confliction system, and we have now acquired that, at the CJTF headquarters. So now there's two nodes for de-confliction with the Russians. The Air Forcethe air component has their node, and we now have a node here at the CJTF headquarters, so we can do that.

I think that this becomes—this -- it becomes almost a daily fact of life. In fact, we probably talked to the Russians, between the air component and my headquarters, we talk to the Russians—somebody's talking to the Russians multiple times a day to de-conflict our operations.16

As U.S. operations in Syria shifted east to the Islamic State's self-declared capital at Raqqah in June 2017, additional de-confliction measures were put in place to keep respective forces and their allies separate as they operated in the middle Euphrates River valley (sometimes shortened to MERV). 17 According to Defense Secretary Mattis, the de-confliction line runs along the Euphrates River, with pro-Syrian and Russian forces operating to the west and U.S.-backed Syrian Democratic Forces (SDF) operating to the east.18 In August, Secretary Mattis acknowledged that the execution of the de-confliction arrangement is complex, stating, "...every day, it's more and more work, as we come closer and closer together." 19

On September 16, Russian aircraft and Syrian government forces struck an SDF position east of the Euphrates River in Deir ez Zor province.20 Following the strikes, senior Coalition and Russian officers held a face-to-face meeting described by a military spokesperson as the first meeting between ground commanders "at the general officer level on both sides." 21 They reportedly discussed expanded de-confliction measures aimed at avoiding "inadvertent" fire between the respective sides. On September 25, Syrian forces conducted artillery strikes near SDF positions north of Deir ez Zor. Coalition forces were not in the area at the time.22

Recent Developments


SDF Operations in Raqqah

On June 6, 2017, the SDF announced the beginning of operations to retake the provincial capital of Raqqah. SDF operations in Raqqah province have been ongoing since November 2016, when the group first launched its campaign (dubbed "Euphrates Wrath") to isolate Raqqah city, the self-declared capital of the Islamic State. As of late September, U.S. military officials estimated that more than 75 percent of the city was under the control of SDF forces.23 The Raqqa Internal Security Forces (RISF), a majority-Arab local force comprised of about 1,600 trained volunteers, has worked to provide security and prevent IS fighters from returning to cleared neighborhoods, while the Raqqah Civil Council provides food and supplies to returning residents. 24 However, SDF operations in Raqqah continue to face challenges such as vehicle borne IEDs and the use of the remaining population as human shields. As of late September, U.S. military officials estimated that about 400-800 IS fighters remained within a roughly four square kilometer area of Raqqah.25


Syrian Democratic Forces (SDF). The SDF has led the operation to isolate Raqqah city, as well as operations inside the city itself. Established in late 2015 as an umbrella group largely led by and made up of Kurdish YPG fighters, the SDF has adjusted its forces over time to more closely reflect the demographics in its areas of operation. In August, U.S. military officials described the SDF as a force comprised of roughly 50,000 fighters, divided evenly between Syrian Kurds and Syrian Arabs.26 Noting the SDF's limitations, Lieutenant General (LTG) Townsend, then-Commander of Combined Joint Task Force-Operation Inherent Resolve (CJTF-OIR), stated:

You have to remember that the Syrian Democratic Forces are not the Iraqi Security Forces. They do not have tanks, helicopters or fighter jets. They are really an irregular light infantry force with a comparative handful of light armored vehicles and heavy weapons, who, with coalition assistance, are fighting well above the weight class."27

Syrian Arab Coalition (SAC). The Syrian Arab Coalition is a term used by U.S. military officials to describe ethnic Arab elements of the SDF. There are few publicly available details on which individual groups constitute the SAC.28

YPG. U.S. officials and other observers acknowledge that the YPG continues to play a leading role in SDF operations.29 Turkey considers the YPG and its political parent organization (the Democratic Union Party, or PYD) to be the Syrian arm of the Kurdistan Workers Party (PKK), which both Turkey and the United States have designated as a terrorist group. Turkey appears to view the YPG as the top threat to its security, given the operational and moral support YPG military and political success could provide to the PKK's insurgency within Turkey.30 The United States does not view the PYD/YPG as a terrorist organization.31 However, a number of sources point to evidence of close and continuing operational and personnel links between the PKK and PYD/YPG.32

Arming Syrian Kurds

On May 9, the Pentagon released a statement saying that President Trump has authorized it "to equip Kurdish elements of the [SDF] as necessary to ensure a clear victory over ISIS in Raqqa."33 Partly in response to Turkish sensitivities about the possibility for YPG elements to aid PKK operations against government personnel in Turkey, the Pentagon spokesperson for anti-IS operations (aka Operation Inherent Resolve, OIR) indicated in a briefing that U.S. arms transfers to Kurdish forces would be "metered out" for specific operations, with the flow monitored to prevent the arms' diversion.34 While President Erdogan and other Turkish officials responded to the May 9 statement with strong criticism, Secretary of Defense Jim Mattis said on May 10 that U.S. officials would work to address Turkish concerns regarding security at its southern border.35 During an August 2017 visit to Turkey, Mattis reportedly discussed assisting Turkey with intelligence on possible PKK targets in Iraq, including the PKK's longtime safe haven in the Qandil Mountains near the Iranian border, and an outpost in the northwestern area of Sinjar that the PKK has built up over the past two years.36

U.S. Forces. The United States provides wide-ranging support to SDF operations against the Islamic State in Raqqah province. This includes training, air support, small arms, ammunition, supplies, and equipment. Prior to May 2017, U.S. officials stated that weapons had been provided only to the non-Kurdish elements within the SDF,37 although one media report cited a U.S. defense official saying that the YPG had already acquired sophisticated U.S.-origin night-operating gear via "other means by other sources."38

Some U.S. troops have been co-located with SDF forces near Raqqah since late 2015. A small contingent of 50 U.S. Special Operations Forces (SOF) initially deployed to northern Syria in October 2015 to support operations against the Islamic State. In April 2016, their numbers were increased by 250. On December 10, then-Defense Secretary Carter announced that the force management level (FML) for U.S. personnel in Syria would be increased to potentially allow the deployment of up to 500 individuals, including special operations forces trainers, advisors, and explosive ordnance disposal teams.39 In August, LTG Townsend described U.S. operations in Syria as largely "SOF-led" with general purpose forces providing additional support. 40

In March 2017, roughly 300 members of the 11th Marine Expeditionary Unit deployed to Syria to assist SDF operations in Raqqah; an additional 100 Army Ranger forces deployed to the city of Manbij in Aleppo province.41 A U.S. military spokesperson stated that the deployment of the Marines to Raqqah was an example of the ability of coalition leaders to "bring in capabilities on a temporary basis to meet specific objectives."42 The Marines have provided heavy artillery support to SDF operations, such as the successful operation in late March to seize Tabqa airfield.43

U.S. military operations in support of the SDF in Syria fall under Combined Joint Task Force – Operation Inherent Resolve (CJTF-OIR), which leads the international coalition to defeat the Islamic State in Iraq and Syria. In September 2017, LTG Paul Funk assumed command of CJTF-OIR, relieving LTG Stephen Townsend, who had commanded the U.S.-led coalition since August 2016.

Operations in Deir ez Zor

As operations against the Islamic State in Raqqah progressed, IS fighters moved east into neighboring Deir ez Zor, which borders Iraq's Anbar province. Deir ez Zor is rich in oil and gas fields, making it valuable to all sides in the conflict, and it has been a focus of Coalition airstrikes in the broader anti-IS campaign. Both the Syrian government and the Syrian opposition have sought to gain territory lost by the Islamic State in Deir ez Zor, in an apparent push to capture areas before they can be claimed by rival forces.

In September, Syrian and Russian forces advancing east from Homs broke a three-year IS siege on Deir ez Zor military airport, and linked up with Syrian military units previously isolated in the city.44 They cleared the road connecting the central crossroads of Palmyra to Deir ez Zor, connecting the city to regime strongholds in western Syria. As of October, Syrian government operations appeared aimed at re-capturing Syria's primary border crossing with Iraq at Abu Kamal, which U.S.-backed forces based at At Tanf unsuccessfully tried to wrest from IS control in 2016.

Meanwhile, SDF forces in September began operations to clear IS fighters from the Khabur River Valley, northeast of Deir ez Zor city.45 The possible convergence of U.S.- and Russian-backed forces in Deir ez Zor has increased focus on de-confliction processes. A U.S. military spokesperson in mid-September stated, "The de-confliction line that starts south of Tabqa and runs west to east and parallels the Euphrates River is holding as regime forces and SDF forces remain in agreed-upon areas."46

However, on September 18 Syrian government forces—assisted by a Russian pontoon bridge and amphibious vehicles—crossed to the eastern bank of the Euphrates in violation of the de-confliction line. Following the move, U.S. officials stated that Coalition-backed and Russian forces are still operating in largely discrete areas, with the former fighting the Islamic State in Deir ez Zor province and the latter fighting further south in Deir ez Zor city.47

Figure 2. Eastern Syria

Euphrates River Valley

However, officials have since acknowledged the presence of some regime elements on the east side of the river.48 U.S. military officials have stated that SDF forces do not plan to enter Deir ez Zor city, adding that the SDF maintains a line of communication with the Syrian government.49 When asked whether the United States preferred that its local partners, rather than the regime, re-capture key areas of Deir ez Zor, a military spokesperson replied, "The priority is, completing the elimination of ISIS in the Euphrates river valley. I think we're neutral on who actually does that work as long as the work is accomplished."50

Syria-Iraq-Jordan Tri-border Area

In 2016, U.S.-backed forces established a base of operations in southeastern Syria near the At Tanf border crossing with Iraq. At Tanf, also located near the Syria-Jordanian border in what is known as the tri-border area, was captured by Syrian rebels in March 2016 from Islamic State fighters.51 As of June 2017, U.S. military officials stated that Coalition and local partner forces each maintained "a couple hundred" troops in At Tanf.52

OIR officials have described the U.S. presence at At Tanf as helping partnered forces reduce the Islamic State's freedom of movement.53 Partnered forces at At Tanf include groups such as Maghawir al Thawra (previously known as the New Syrian Army), some of whom were trained during the initial phase of the Defense Department's Syria Train and Equip program.54 Describing ongoing coalition operations in the area around At Tanf, an OIR spokesperson in early May stated,

The U.S. and coalition special operations forces continue to advise, assist and accompany vetted Syrian opposition partner forces through the Hamad Desert. Vetted Syrian opposition groups continue to clear ISIS from the towns and villages around the An Tanf border crossing between Iraq and Syria. This secure border facilitates the passage of 500 to 900 people each day, opening up opportunities for local goods to flow in and out of Syria, stimulating the economy for the people.55

In late July, 2017, a U.S. military spokesperson announced that the Coalition would no longer support one of its partner forces, Shuhada al Qaryatayn, part of the Syrian vetted opposition that had received weapons and equipment as part of the Syria Train and Equip Program. Describing the group as "important partners in the fight against ISIS in southern Syria," U.S. military officials stated that the At Tanf-based group had "conducted patrols outside of the agreed upon de-escalation zone and engaged in activities not focused on fighting ISIS."56 According to media sources, the group had conducted attacks against Syrian government forces. Shuhada al Qaryatayn continues to operate in the At Tanf area. U.S. military officials stated that the group had returned the heavy weapons and other equipment provided to them for the counter-IS campaign, but were permitted to keep some small arms and light vehicles.57

Coalition forces have established temporary de-confliction zones in areas where its partner forces are based, including a 55-kilometer zone around At Tanf.58 Since May 2017, U.S. forces have conducted strikes against pro-Asad militia fighters that have infiltrated the de-confliction area around At Tanf, as well as strikes against Syrian government forces that have targeted local U.S. partner forces in other parts of the country. On June 18, a U.S. fighter aircraft shot down a Syrian SU-22 bomber south of the Syrian city of Al Tabqa in Raqqah province. The Syrian aircraft had dropped bombs near SDF forces in the area. The incident, described by U.S. officials as "collective self-defense of Coalition partner forces," was the first time the U.S. military had downed a manned Syrian aircraft during the conflict.59

Chronology of Recent U.S. Defensive Strikes in Syria


U.S. forces strike pro-Syrian government land forces near At Tanf.


U.S. forces strike pro-Syrian government land forces near At Tanf.


U.S. F-15 shoots down an Iranian-made Shahed 129 drone near At Tanf.


U.S. F/A-18E Super Hornet shoots down Syrian SU-22 south of Al Tabqa (near Ja'din).


U.S. F-15 shoots down an Iranian-made Shahed 129 drone north of At Tanf (near Zaqaf).

In September, U.S. military officials announced the closure of the Zaqaf outpost, located roughly 45 miles north of At Tanf, a few miles from the Syria-Iraq border. Opposition sources suggested that the U.S. decision to close Zaqaf was made as part of an agreement with Russia, but a Pentagon spokesperson stated that "the decision to establish and close bases are determined by operational requirements and the progress of the campaign."60

Rukban Camp

According to UN estimates as of early August 2017, roughly 50,000 Syrians remained stranded at the makeshift Rukban camp near the Syrian-Jordanian border (see Figure 2). Rukban is located in a remote desert area along what is known as the Berm—earthen mounds that mark the border between Syria and Jordan. A June 2016 suicide bombing at Rukban led Jordanian authorities to declare the area a closed military zone, barring humanitarian workers from entering the area. The Jordanian government allows small numbers of camp residents to enter Jordan to receive medical treatment; they must then return to Rukban.61

As Syrian government forces advanced in an effort to regain control of southern border areas with Jordan, thousands of Syrians residing at the nearby Hadalat camp fled to Rukban—increasing that camp's population to an estimated 60,000 people.62 At the same time, UN officials have noted that "...the establishment a Government of Syria-controlled corridor from Damascus to Iraq, north of the berm, has effectively trapped the population, restricting the movement of both people and goods to the area."63 Citing security concerns, Jordan's government does not permit Syrians at Rukban to seek asylum inside the kingdom.

Unlike Hadalat, the Rukban camp is located within the 55-kilometer de-confliction area established by Coalition forces around At Tanf. While protecting the Rukban camp is not part of the Coalition's mission, there are concerns about the safety of the camp's population if Coalition forces were to withdraw.64

Ongoing U.S. Presence in Manbij

U.S. military personnel continue to operate in the northern Syrian town of Manbij, located in Aleppo province roughly 40 km from the Turkish border. SDF forces captured Manbij from the Islamic State in August 2016, and coalition forces remained in the city. Following the expulsion of IS forces from Manbij, Turkey expressed concern that Kurdish YPG fighters might retain a permanent presence in the city, putting the group a step closer to establishing a contiguous area of Kurdish control along the Turkish border (see Figure 1). Less than two weeks after the SDF operation in Manbij, Turkish forces crossed into northern Syria in what it termed Operation Euphrates Shield (see "Turkish-Supported Operations in Syria," below).

Governance in Manbij was assumed by the Manbij Military Council, and coalition forces in the city continued to "train, advise, assist and accompany" Manbij Military Council forces as they worked to provide security and restore governance.65 In March 2017, approximately 100 Army Rangers were deployed to Manbij. The visible deployment of additional U.S. forces to Manbij appeared designed to deter conflict between rival groups in the vicinity, which include Kurdish, Turkish, Russian, and Syrian forces. A U.S. military spokesperson stated that the U.S. presence in Manbij "improves transparency and facilitates communication among all parties in the area to avoid misunderstanding and miscalculation."66 He acknowledged that U.S. and Russian forces in Manbij are in close enough proximity that they can visually observe one another's movements, and that communication between the two continues to increase via the de-confliction channel.67

On August 10, an OIR spokesperson stated that small arms fire had been directed at U.S. forces on patrol in Manbij, stating, "...over the course of the last week, there have been clear, direct fire engagements that have not resulted in injury or damage to equipment, but near our forces."68 The official stated that "we do not know who is behind these attacks," but noted that U.S. patrols in Manbij are overt and that "our forces are clearly marked." U.S. forces did not return fire, but the official said that U.S. forces were prepared to defend themselves if required.

In late August, LTG Townsend reported that the situation had stabilized, stating,

...what we were seeing about two weeks ago were some of the Free Syrian Army oppositionSyrian opposition fighters in the area controlled by the Turk military were firing upon the Manbij area there, where there are some U.S. forcescoalition forces there. We identified this to our Turkish alliesour NATO allies, Turkey, and they have, I think, taken the appropriate measures to get that under control ...Turkey's done great work with the coalition, and I think that they've gotten that under control, and I think we had some opposition unitselements there on their side that were kind of acting on their own, and I believe it's gottenit's been put under control now.69

Turkish-Supported Operations in Syria

Turkish operations inside Syria (known as Operation Euphrates Shield) began in August 2016, and were designed to counter both Islamic State and Kurdish forces operating along Turkey's southern border with Syria.70 Since then, Turkish forces have worked with allied Syrian forces (mostly Arabs and Turkmen nominally opposed to the Asad regime) to counter IS fighters, but also have clashed with Syrian Kurdish-led forces. Turkey's operations in northern Syria appear to reflect Turkish concerns that the YPG fighters in Syria could create a contiguous area of Kurdish control along the Turkish border.

In March 2017, Turkish leaders announced that Operation Euphrates Shield had been "successfully completed," but did not specify when or if Turkish troops would withdraw from Syria.71 Turkish Prime Minister Binali Yildirim noted that Turkey could launch further military operations if necessary, under a different name.

On April 25, Turkish aircraft bombed a PYD/YPG outpost in Syria's eastern province of Hasakah as part of a larger operation that also targeted PKK installations in the Sinjar area of northwest Iraq. A YPG spokesperson reported that the Turkish strike killed 20 and wounded 18 others, while Turkey's military stated that the strike's purpose was to prevent the PKK from sending weapons across the border into Turkey.72 A State Department spokesperson stated that

we are very concerned–deeply concerned–that Turkey conducted airstrikes earlier today in northern Syria, as well as northern Iraq, without proper coordination either with the United States or the broader global coalition to defeat ISIS. And we've expressed those concerns to the Government of Turkey directly. These airstrikes were not approved by the coalition and led to the unfortunate loss of life of our partner forces in the fight against ISIS that includes members of the Kurdish Peshmerga.73

One report cited a claim from a Syrian Kurdish official (corroborated by an unnamed coalition official) that some U.S. special forces in Syria had been "uncomfortably close" to the site of the Turkish strike.74 A State Department spokesperson acknowledged Turkey's concerns about the threat posed to it by the PKK, but stated that coordination in the battle space was critical, both to maintain pressure on the Islamic State and to "ensure the safety of all coalition personnel."75 In August, clashes continued between YPG and Turkish-backed forces in northern Syria, particularly around the Kurdish-held canton of Afrin, and Turkish officials suggested that Ankara may expand operations into Afrin and other Kurdish-held parts of Syria.76

Figure 3. Syria-Turkey Border

Source: CRS using area of influence data from IHS Conflict Monitor, last revised September 26, 2017. All areas of influence approximate and subject to change. Other sources include U.N. OCHA, Esri, and social media reports.

On October 7, 2017, Turkish President Recep Tayyip Erdogan announced a new operation in Syria's Idlib province aimed at preventing the expansion of both Kurdish and Al Qaeda-linked forces along the Turkish border. 77 Idlib province is dominated by the Levant Liberation Committee (Hay'a Tahrir al Sham, HTS), which has ties to Al Qaeda and was formerly known as the Nusra Front. According to President Erdogan, the operation would be led by Syrian opposition forces backed by Turkish units and Russian air support. 78 U.S. officials stated that the United States would not be participating in the operation but expressed support for Turkey's efforts to secure its borders and fight terrorism.79 The operation appears to be linked to the Astana negotiations (see "The Astana Process," below) whereby Russia, Turkey, and Iran agreed to create de-escalation areas in Syria—including one in Idlib province. Turkish forces in mid-September bolstered their presence along the Syrian border, and on October 9 Turkey announced that it had moved soldiers into Idlib province to conduct "reconnaissance activities."80

For additional background, see CRS Report R44513, Kurds in Iraq and Syria: U.S. Partners Against the Islamic State, coordinated by [author name scrubbed].

Political Negotiations

The Geneva Process

Since 2012, the Syrian government and opposition have participated in U.N.-brokered negotiations under the framework of the Geneva Communiqué. Endorsed by both the United States and Russia, the Geneva Communiqué calls for the establishment of a transitional governing body with full executive powers. According to the document, such a government "could include members of the present government and the opposition and other groups and shall be formed on the basis of mutual consent."81 The document does not discuss the future of Asad.

Subsequent negotiations have made little progress, as both sides have adopted differing interpretations of the agreement. The opposition has said that any transitional government must exclude Asad. The Syrian government maintains that Asad was reelected (by referendum) in 2014,82 and notes that the Geneva Communiqué does not explicitly require him to step down. In the Syrian government's view, a transitional government can be achieved by simply expanding the existing government to include members of the opposition. Asad has also stated that a political transition cannot occur until "terrorism" has been defeated.

In February, March, and May 2017, representatives from the Syrian government and Syrian opposition groups met for indirect talks in Geneva, facilitated by U.N. Envoy Staffan de Mistura. The talks did not make significant progress. The last round of talks was held in Geneva on July 10-14, and De Mistura has called for the next round to be held in late October or early November.

In September 2017, Acting Assistant Secretary for Near Eastern Affairs David Satterfield stated that there would not be international participation in the reconstruction of Syria without a credible political process. Satterfield added, " the extent that the opposition can focus on Geneva as the venue for advancing their political goals, we think they can be more influential in achieving the results they want for themselves and above all for the Syrian people they represent."83

The Astana Process

In December 2016, the foreign and defense ministers of Russia, Iran, and Turkey met in Moscow to discuss a political resolution to the Syrian conflict. The parties issued a joint statement, which laid out a set of principles for a future peace deal. While acknowledging that the United States was not asked to participate in the talks, a State Department spokesperson characterized the joint statement as "borrowing …from ideas that the United States has led and pushed from the outset."84 On December 29, Russia and Turkey announced a new cease-fire agreement to be followed by peace talks in Kazakhstan within a month, cosponsored by both countries.85 On December 31, the U.N. Security Council unanimously adopted Resolution 2236, welcoming and supporting the Russian-Turkish initiative.

Three rounds of peace talks were subsequently held in the Kazakh capital of Astana, all of which closed with few results. On May 3-4, the fourth round of talks was held at Astana, resulting in the issuance of a memorandum on the creation of de-escalation areas in Syria. Following subsequent rounds of talks in July and September, the parties issued a joint statement on September 15 announcing the establishment of the de-escalation areas per the May 4 memorandum.86 The next round of Astana talks is scheduled for late October.

De-escalation Areas. On May 4, 2017, representatives of Russia, Iran, and Turkey at Astana signed a memorandum on the creation of "de-escalation areas" inside Syria. The areas are to be located in four noncontiguous parts of Syria: Idlib province and its surroundings, some parts of northern Homs province, eastern Ghouta in the Damascus suburbs, and parts of the southern provinces of Dar'a and Quneitra. The memorandum calls for hostilities between the Syrian government and opposition to cease within the de-escalation areas. The memorandum also calls for unhindered humanitarian access within these areas, as well as measures to restore infrastructure and encourage the voluntary return of refugees and internally displaced persons. Neither the Syrian government nor representatives of Syrian opposition groups signed the memorandum. The September memorandum states that maps specifying the boundaries of the de-escalation areas were agreed upon during meeting on September 8th in Ankara.

Security Zones. The May 4 memorandum also states that, "along the lines of the de-escalation areas, security zones shall be established in order to prevent incidents and military confrontations between the conflicting parties." The security zones are to include checkpoints to ensure "unhindered movement of unarmed civilians" and the delivery of humanitarian aid, as well as observation posts to ensure compliance with the ceasefire. The security zones and the checkpoints and observation posts within them are to be administered by "forces of the Guarantors" (Russia, Turkey, and Iran). The agreement also notes that "third parties" might be deployed for this purpose, with the consensus of the guarantors.

Reactions. The agreement, which went into effect on May 5, has reportedly resulted in a reduction—but not cessation—of violence, and clashes have continued in regions expected to form part of the de-escalation areas.87 The Syrian government has said that it will abide by the agreement if the opposition does, adding that Syria will continue to fight what it describes as terrorist groups. The Syrian High Negotiations Committee, which represents a number of Syrian opposition groups in U.N.-brokered talks in Geneva, criticized the agreement as an attempt to "partition the country" and rejected the role of Iran as a guarantor.88 The State Department issued a statement noting that the United States "supports any effort that can genuinely de-escalate the violence in Syria," but expressing concerns about "the involvement of Iran as a so-called 'guarantor.'"89

Next Steps. As part of the September 15 memorandum, Russia, Iran, and Turkey agreed to form a joint coordination center to coordinate the activities of their respective forces in the de-escalation areas. A Russian official stated that the three countries planned to send about 500 observers to Syria's Idlib province, including Russian military police.90 According to one Turkish media report, Idlib province will be divided into three operational zones with Turkish forces and Syrian opposition groups based in the northwest near the Turkish border, Syrian government and Iranian forces deployed to the southeast, and Russian forces stationed in the middle.91

Remaining Questions.

Humanitarian Situation

U.S. Humanitarian Assistance

The United States is the largest donor of humanitarian assistance to the Syria crisis, drawing from existing funding from global humanitarian accounts and some reprogrammed funding.93In September 2017, the State Department announced $697 million in additional humanitarian aid, bringing total U.S. humanitarian assistance for the Syria crisis to nearly $7.4 billion since 2011.94

In December 2016, the Further Continuing and Security Assistance Appropriations Act, 2017 (P.L. 114-254), made funds available at FY2016 levels primarily through the Migration and Refugee Assistance (MRA) and International Disaster Assistance (IDA) accounts. Division B of the act provided an additional $916 million in FY2017 supplemental funding through MRA and IDA for the humanitarian response in Iraq and Syria. The Consolidated Appropriations Act, 2017 (P.L. 115-31) provides funding to several global humanitarian accounts, including $3.058 billion in MRA and $3.811 billion in IDA, some of which will be used to respond to the Iraq-Syria crises.

The Trump Administration's FY2018 appropriations request seeks more than $2.5 billion in enduring and OCO funding for the IDA account, some of which would be used to respond to the Iraq and Syria crises. The Administration also seeks more than $2.7 billion for the MRA account, including $1.2 billion for MRA-funded programs in the Near East region.

In the December 2016 continuing resolution, $1 billion in Economic Support Funds-OCO (ESF-OCO) was appropriated for stabilization and community support in Syria, some of which may be used for humanitarian activities.

In the FY2017 Consolidated Appropriations Act, a Relief and Recovery Fund, established under Section 8004, using ESF, INCLE, Peacekeeping, and FMF accounts provides $169 million for Iraq and Syria on a range of activities, some of which could be considered humanitarian. None of these figures include emergency food aid appropriated to the Food for Peace program (P.L. 480, Title II). Country allocations of funds appropriated in the FY2017 omnibus (P.L. 115-31) will be determined through consultations between Congress and the executive branch.95

International Humanitarian Funding

Multilateral humanitarian assistance in response to the Syria crisis includes both the Regional Refugee and Resilience Plan (3RP) and the Humanitarian Response Plan (HRP). The 3RP is designed to address the impact of the conflict on Syria's neighbors, and encompasses the Lebanon Crisis Response Plan, the Jordan Response Plan, and country chapters in Turkey, Iraq, and Egypt. It includes a refugee/humanitarian response coordinated by UNHCR and a "resilience" response (stabilization-based development assistance) led by UNDP.96

In parallel to the 3RP, the HRP for Syria is designed to address the crisis inside the country through a focus on humanitarian assistance, civilian protection, and increasing resilience and livelihood opportunities, in part by improving access to basic services. This includes the reconstruction of damaged infrastructure (water, sewage, electricity) as well as the restoration of medical and education facilities and infrastructure for the production of inputs for sectors such as agriculture.97 The 2017 3RP appeal seeks $5.6 billion, and the HRP for Syria seeks $3.4 billion. As of October 2017, the two appeals were funded at approximately 45% and 37%, respectively.

For additional details on the humanitarian situation in Syria, see CRS In Focus IF10648, Syria's Humanitarian and Protection Crisis: Current Status, by [author name scrubbed].

U.S. Policy and Assistance

Perceived Threats and Challenges for Policymakers

Syria's descent into chaotic conflict over the past six years has generated several interrelated threats to U.S. national security and challenges for U.S. decisionmakers. Direct threats to U.S. security and interests include the following:

The above threats have challenged U.S. policymakers by

U.S. concerns about these threats and challenges have evolved in relation to developments in the Syria conflict and changes in its international context, with executive branch officials and Members of Congress assigning different priority to different issues over time. Overall, the United States has balanced several basic objectives: securing an end to the conflict, ridding Syria of chemical weapons, and fighting violent Islamist extremist groups active in Syria.

U.S. Strategy and Policy

One central question for U.S. policy toward the Syria conflict since 2011 has been whether or not the United States should support and pursue a resolution of the conflict that would recognize a continuing role for Syrian President Bashar al Asad. Policy proposals over time have reflected various assumptions about whether Asad's continued rule or its end would bring the conflict to a close. Counterterrorism and regional stability concerns became amplified by developments in Syria's underlying conflict and arguably, in the case of the Islamic State, took precedence over U.S. concerns about Asad's future. U.S. and regional policymakers have sought to determine which problem in Syria to confront first—Asad or the Islamic State—and U.S. officials and observers have debated how different approaches and outcomes would affect Syria's short- and long-term stability.

Syria Policy Under the Obama Administration

In 2011, the Obama Administration called for Syrian President Bashar al Asad to step down amid protests in Syria inspired by the "Arab Spring." This call was based in part on concern that, if left unchallenged, the Syrian government's use of force against demonstrators would set a dangerous precedent that political violence against civilians could continue unchecked. Asad refused to leave office, and the conflict intensified. Humanitarian pressures and threats posed by terrorist groups grew.

President Barack Obama and his Administration pursued various policies to protect U.S. interests with regard to Syria, while implementing an overarching regional strategy that prioritized efforts to freeze Iran's nuclear program and reduce the direct involvement of U.S. military forces in combat operations. The Obama Administration engaged from 2012 through 2017 in multilateral efforts to reach a negotiated settlement to the conflict that would result in Asad's departure but preserve some elements of the Syrian government. This approach was informed by parallel U.S concerns about terrorism and efforts to contain and defeat violent Islamist extremist groups active in Syria, principally the Al Qaeda-affiliated Nusra Front and the Islamic State organization.

The Obama Administration sought to bolster its diplomacy and counterterrorism policy toward Syria through the provision of nonlethal U.S. support to select Syrian opposition groups, reported covert assistance to some armed groups, and overt training and lethal assistance to certain vetted Syrian forces. Obama Administration officials often asserted that there was "no military solution to the conflict." That formulation appeared to reflect the Administration's stated preference for the conflict to be brought to a close in a way that would preserve some elements of the Syrian state apparatus rather than allowing military developments to result in state collapse or the outright victory of pro-Asad forces.

As the Trump Administration has begun articulating its approach to Syria in 2017, the underlying conflict in Syria and associated counterterrorism, humanitarian, and international systemic challenges that vexed the Obama Administration have persisted. President Trump and the Administration have identified the defeat of the Islamic State organization as their highest priority in the Middle East, and President Trump directed his Administration in January to develop "a new plan to defeat ISIS."

On April 6, Secretary of State Rex Tillerson outlined the Trump Administration's vision for the sequencing of U.S. efforts, subject to developments in Syria:

Overall, the situation in Syria is one where our approach today and our policy today is first to defeat ISIS. By defeating ISIS, we remove one of the disruptive elements in Syria that exists today. That begins to clarify, for us, opposition forces and regime forces, and working with the coalition—as you know, there is a large coalition of international players and allies who are involved in the future resolution in Syria.

So it's to defeat ISIS; it's to begin to stabilize areas of Syria, stabilize areas in the south of Syria, stabilize areas around Raqqa, through cease-fire agreements between the Syrian regime forces and opposition forces; stabilize those areas, begin to restore some normalcy to them, restore them to local governments—and there are local leaders who are ready to return, some who've left as refugees that are ready to return, to govern these areas; use local forces that will be part of the liberation effort to develop the local security forces—law enforcement, police force; and then use other forces to create outer perimeters of security so that areas like Raqqa, areas in the south, can begin to provide a secure environment so refugees can begin to go home and begin the rebuilding process.

In the midst of that, through the Geneva process, we will start a political process to resolve Syria's future in terms of its governance structure. And that ultimately, in our view, will lead to a resolution of Bashar al-Assad's departure.98

President Trump has discussed the possibility of establishing "safe zones" in Syria, but to date the Administration has not publicly defined what such an initiative might entail or signaled an intent to pursue it imminently. The April 2017 chemical weapons attack, the U.S. military response, and subsequent incidents involving U.S. defensive strikes on Syrian government forces appear to have complicated the Trump Administration's attempts to pursue a more cooperative relationship with the Russian government with regard to the conflict. U.S. efforts to contain or more aggressively curtail Iran's security support for its foreign partners may also affect developments in Syria. Administration officials in August described U.S. policy in Syria as encompassing two phases, with the first focusing on the defeat of the Islamic State and the second on the "de-escalation" of violence in Syria, including through ceasefire agreements.99

Members of Congress may similarly reassess U.S. priorities and strategy in Syria and may consider a range of general and specific questions as the Trump Administration develops and seeks congressional support for its approach.

Congress has directed President Trump to transmit a report describing a strategy for Syria within 90 days of the enactment of the FY2017 Consolidated Appropriations Act (Section 10006 of Division C of P.L. 115-31, which became law May 5, 2017). In his signing statement on the act, President Trump identified this reporting requirement as a provision that would "mandate or regulate the submission of certain executive branch information to the Congress," and said, "I will treat these provisions in a manner consistent with my constitutional authority to withhold information that could impair foreign relations, national security, the deliberative processes of the executive branch, or the performance of my constitutional duties."100

U.S. Assistance to Syrians and the Syrian Opposition

A broad set of bilateral U.S. sanctions on Syria existed prior to the outbreak of conflict, and some, such as those triggered by Syria's designation as a state sponsor of terrorism, initially had a limiting effect on the delivery of U.S. assistance in the country. The FY2014 Consolidated Appropriations Act (Section 7041[i]) of Division K of P.L. 113-76) significantly expanded the Administration's authority to provide nonlethal assistance in Syria for certain purposes using the Economic Support Fund (ESF) account. Such assistance had been restricted by a series of preexisting provisions of law (including some terrorism-related sanctions provisions) that required the President to assert emergency and contingency authorities (i.e., Sections 451 and 614 of the Foreign Assistance Act of 1961, as amended) to provide such assistance to the unarmed Syrian opposition and communities in Syria. Such assistance has been provided to select unarmed opposition groups on a periodic basis since May 2012, although the Administration has not publicly released a detailed accounting or list of recipients. Congressional committees of jurisdiction are notified when the Administration intends to obligate funds for these purposes.

The FY2014 assistance authorities, as expanded and extended by the FY2015 Appropriations Act (Section 7041[h] of P.L. 113-235), made FY2015 and prior year ESF funding available "notwithstanding any other provision of law" for select nonlethal purposes. The FY2016 Appropriations Act (Section 7041[h] of P.L. 114-113) extended this authority further, granting notwithstanding exceptions for FY2016 ESF funds as well as for FY2016 funds in the International Narcotics Control and Law Enforcement (INCLE) and Peacekeeping Operations (PKO) accounts. The Obama Administration used the INCLE and PKO accounts to support justice sector activities in opposition-held areas of Syria and to provide nonlethal assistance to select armed opposition groups.

The FY2017 Consolidated Appropriations Act (Section 7041[j] of Division J of P.L. 115-31) amended and expanded the categories of assistance authorized in FY2016 (changes italicized below) to include "non-lethal assistance for programs to address the needs of civilians affected by conflict in Syria, and for programs that seek to—

(A) establish governance in Syria that is representative, inclusive, and accountable;

(B) empower women through political and economic programs, and address the psychosocial needs of women and their families in Syria and neighboring countries;

(C) develop and implement political processes that are democratic, transparent, and adhere to the rule of law;

(D) further the legitimacy and viability of the Syrian opposition through cross-border programs;

(E) develop and sustain civil society and independent media in Syria;

(F) promote stability and economic development in Syria;

(G) document, investigate, and prosecute human rights violations in Syria, including through transitional justice programs and support for nongovernmental organizations;

(H) expand the role of women in negotiations to end the violence and in any political transition in Syria;

(I) assist Syrian refugees whose education has been interrupted by the ongoing conflict to complete higher education requirements at universities and other academic institutions in the region, and through distance learning;

(J) assist vulnerable populations in Syria and in neighboring countries;

(K) protect and preserve the cultural identity of the people of Syria as a counterbalance to extremism, particularly those living in neighboring countries and among youth;

(L) protect and preserve cultural heritage sites in Syria, particularly those damaged and destroyed by extremists; and

(M) counter extremism in Syria.

The FY2017 act requires the Secretary of State to "take all practicable steps to ensure that mechanisms are in place for the adequate monitoring, oversight, and control of such assistance inside Syria," and requires the Secretary of State to "promptly inform the appropriate congressional committees of each significant instance in which assistance provided pursuant to this subsection has been diverted or destroyed, to include the type and amount of assistance, a description of the incident and parties involved, and an explanation of the response of the Department of State."

The act further requires the Trump Administration to update a previously required comprehensive interagency strategy prior to using the authorities. That strategy must include a "mission statement, achievable objectives and timelines, and a description of inter-agency and donor coordination and implementation of such strategy." The strategy, which may be classified, must also include "a description of oversight and vetting procedures to prevent the misuse of funds." All funds obligated pursuant to the authorities are subject to established congressional notification procedures.

The U.S. Syria Transition Assistance and Response Team operates from Turkey and coordinates U.S. assistance to Syria, including assistance to opposition-held areas. The State Department requested more than $480 million in FY2016 and FY2017 funding to provide nonlethal support to vetted, moderate armed opposition groups, other opposition actors, and communities in opposition-held areas of Syria. Section 7041(j) of Division J of the Consolidated Appropriations Act, 2017, allows certain accounts to fund "non-lethal assistance for programs to address the needs of civilians affected by conflict in Syria" for select purposes.

The Trump Administration has requested $191.5 million in Overseas Contingency Operation funding for State Department-administered programs in Syria for FY2018, including $150 million in Economic Support and Development Fund-OCO monies.

Nonlethal Assistance to Armed Syrian Opposition Elements

Until the creation of the Syria Train and Equip program in 2014 discussed below, overt U.S. assistance to armed opposition forces remained restricted to nonlethal items. Prior to the creation of the program and the extension of the FY2016 foreign assistance authorities discussed above, congressional appropriators and authorizers had not provided the Administration with notwithstanding authority to provide nonlethal assistance to armed opposition groups. For that purpose, the Obama Administration had relied upon special authorities granted by the Foreign Assistance Act of 1961, as amended (Section 552[c] and Section 614).

In 2012, the Administration began to use these special authorities to provide food rations and medical supplies to the National Coalition of Revolutionary and Opposition Forces (SOC) and the Turkey-based Syrian Military Council (SMC). Since then, U.S. assistance has expanded to encompass a range of smaller, local groups. In August 2015, the State Department reported

Non-lethal assistance is being provided to a range of civilian opposition groups, including local councils, civil society organizations, and SOC-affiliated entities to bolster their institutional capacity, create linkages among opposition groups inside and outside Syria, and help counter violent extremism. These efforts enable the delivery of basic goods and essential services to liberated communities as they step in to fill voids in local governance. In addition to civil administration training programs, we have provided opposition groups with a wide array of critical equipment, including generators, ambulances, cranes, dump trucks, fire trucks, water storage units, search and rescue equipment, educational kits for schools, winterization materials, and commodity baskets for needy families in the local community.101

This equipment is used to bolster governance by providing services such as emergency power, sanitation, water, and education services. Other U.S. assistance provided under authorities granted by Congress in FY2014-FY2016 appropriations acts and the FY2017 continuing resolution supports the maintenance of public safety, rule of law, and the documentation of human rights violations.

Obama Administration officials noted that U.S. efforts to deliver and monitor security assistance and other aid inside Syria have been hindered by border closures, ongoing fighting, and risks from extremist groups. Some U.S. nonlethal assistance to armed opposition groups has fallen into the hands of unintended recipients and has led to changes in delivery and oversight mechanisms.102 Infighting among some opposition forces, the empowerment of the Islamic State in Syria, and concerns expressed by other outside actors such as Russia and Turkey have created further complications. Although the Islamic State has lost control of border crossings it formerly held, other anti-U.S. extremist groups control some border crossings in northwestern Syria. As such, access issues may continue to hinder efforts to expand support to anti-IS forces.

In July 2016, the Government Accountability Office released a report examining the delivery of nonlethal assistance to Syria. The report recommended that the Department of State, USAID, and their implementing partners incorporate greater oversight of fraud risk in the delivery of such aid.103

Syria Train and Equip Program104

Congress authorized and funded a train and equip program for vetted Syrians in 2014 for select purposes, including supporting U.S. efforts to combat the Islamic State and other terrorist organizations in Syria and promoting the conditions for a negotiated settlement to Syria's civil war (Section 1209 of H.R. 3979, P.L. 113-291). The program's limited results as of September 2015, Russian military intervention in Syria, and support by some Members of Congress for broader civilian protection missions led the Obama Administration to alter the program beginning in October 2015. Obama Administration officials described their intended overall approach to the redesigned program as "transactional" and performance-based, with Syrian beneficiaries receiving U.S. support as opportunities presented themselves and relative to their effectiveness on the battlefield and the alignment of their actions with U.S. interests.

The revamped train and equip program has since shifted away from training and equipping "New Syrian Force" units of vetted new recruits and toward "equipping and enabling ... a select group of vetted leaders and their units" inside Syria who are fighting the Islamic State organization. Trained and equipped individuals fight under the rubric of a Kurdish-Arab coalition force in northern Syria known as the Syrian Democratic Forces (SDF) and a force known as the "New Syrian Army" (NSA) in the southeast. Equipment, including some weaponry and ammunition, has been provided to SDF and NSA forces, and U.S. special operations personnel have been deployed to Syria to advise and assist the SDF in operations against the Islamic State.

The shift from training and equipping of new vetted units toward equipping existing vetted armed groups has featured some unique risks. While equipment losses have not proven to be a major systemic concern since the change was announced, some Syrian opposition groups that reportedly have received U.S. equipment and weaponry have surrendered or lost these items to other groups, including to the Islamic State.105 The comprehensive training approach under the program's first iteration sought to create unit cohesion, groom and support reliable leaders to serve as U.S. partners, and inculcate a spirit of nationalist motivation among fighters in the place of local, sectarian, or ideological goals. The amended approach appears to have more rapidly and effectively equipped some anti-IS forces in some areas of Syria, but may have fewer direct effects on the internal development and practices of forces, some of whom may influence security in Syria for years to come. Increased reliance on vetted group leaders may also have reduced direct U.S. visibility and influence over which individual fighters receive U.S.-origin weapons or how U.S.-origin equipment is managed and secured.

Related Appropriations and Authorities

The underlying authority for the Department of Defense Syria train and equip program remains Section 1209 of the FY2015 defense authorization act (P.L. 113-291), as amended and extended by subsequent legislation. Congress has not appropriated funds specifically for the Syria train and equip program since the program's inception. Congress has authorized the reprogramming of funds by the Department of Defense to operations and maintenance accounts to fund program activities, subject to the prior approval of the congressional defense committees. In total, as of May 2017 Congress had reviewed and approved Defense Department requests to reprogram more than $1.25 billion in monies from other accounts for the program since 2014.106

Funding transfers to operations and maintenance accounts for Syria train and equip program activities remain subject to the prior approval of congressional defense and appropriations committees pursuant to the terms of the FY2017 NDAA (P.L. 114-328), which extended the authorization for the program through December 31, 2018. President Obama requested $250 million for the Syria train and equip program for FY2017, and in March 2017, the Trump Administration requested an additional $180 million in FY2017 funds for the program.

As noted above, the FY2017 Consolidated Appropriations Act (Division C of P.L. 115-31) provides $980 million for a Counter-ISIL Train and Equip Fund available until September 30, 2018. The act also makes available an additional $626.4 million for the fund that would provide funding requested by President Trump. These additional funds cannot be obligated or expended until 15 days after the President submits a required report "on the United States strategy for the defeat" of the Islamic State organization (Section 10005 of Division C of P.L. 115-31).

Table 1. Syria Train and Equip Program: Appropriations Actions and Requests

$, thousands


FY2015 Approved Transfers

FY2016 Approved Transfers

FY2017 Approved Transfers

FY2017 Requests

FY2018 Syria-Specific Request



(O&M FY15)


(CTPF FY15/16)


(CTPF FY16/17)






(CTPF FY15/16)


(CTPF FY16/17)


(CTPF FY17/17)





(CTPF FY15/16)







(CTPF FY15/16)





Net Total






Source: Executive branch appropriations requests and reprogramming notifications.

Notes: Counterterrorism Partnerships Fund (CTPF). Counter-Islamic State of Iraq and Syria (ISIS) Train and Equip Fund (CTEF). The authority for the Syria Train and Equip Program requires the Department of Defense to submit prior approval notices to transfer funds into various service and department-wide Operations and Maintenance accounts for program activities. Funds listed were approved for transfer by the required congressional defense and appropriations committees during the fiscal years noted.

The Trump Administration has requested $500 million for Syria train and equip program efforts as part of its FY2018 defense appropriations request for the Counter-IS Train and Equip Fund. The House-engrossed version of the FY2018 NDAA (H.R. 2810) would preserve oversight reporting on the Syria train and equip program. The Senate version does not contain this provision and would set terms and limitations for the use of Syria train and equip program monies for construction. Neither bill would extend the program authority past December 31, 2018.

Proposed Restrictions on Man-Portable Air Defense Systems (MANPADS)

Since 2013, Congress has considered and enacted some proposals to restrict or govern the use of authorized and appropriated funds for the procurement or transfer of man-portable air defense systems (MANPADS) to Syria. Proposed MANPADS restrictions have reflected the concerns of some Members of Congress that MANPADS could fall into the hands of hostile parties and threaten civilian aircraft, allied military aircraft, and U.S. aircraft that are conducting air strikes against terrorist groups or that may otherwise be supporting Syrian groups.

In the 113th Congress, proposals sought to define the types of assistance that could be provided and to place conditions or restrictions on the transfer of certain weapons systems to Syrians (S. 960, H.R. 1327). Section 9016 of the FY2015 defense appropriations act (P.L. 113-235) stated that none of the funds used pursuant to the authorities contained in the section for the Syria Train and Equip program "shall be used for the procurement or transfer of man portable air defense systems."107 Parallel authority for the program was established by Section 1209 of the FY2015 defense authorization act (P.L. 113-291) and extended until December 31, 2018, by the FY2017 NDAA. The Section 1209 authority, as subsequently amended, does not restrict the purchase or transfer of MANPADS pursuant to the authority.

In the 114th Congress, for FY2016, the House-proposed version of the FY2016 defense appropriations act (H.R. 2685) would have authorized and appropriated monies for the continuation of the Syria Train and Equip program and was amended to provide that "none of the funds used pursuant to this authority shall be used for the procurement or transfer of man-portable air-defense systems."108 As enacted, the final version of the FY2016 defense appropriations act (Division C of P.L. 114-113) did not include a Syria-related prohibition on MANPADS procurement or transfer, but provided in Section 9013 that "none of the funds made available by this Act under the heading 'Iraq Train and Equip Fund' may be used to procure or transfer man-portable air defense systems." The 114th Congress considered and the House adopted a proposal for FY2017 that would have prohibited the use of certain funds made available by the act to procure or transfer MANPADS (Section 9013 of the House-passed version of the FY2017 defense appropriations act [H.R. 5293]). The House further adopted an en bloc floor amendment during its consideration of the FY2017 defense authorization bill (incorporated as Section 1229 of H.R. 4909) that included an amendment to prohibit the obligation or expenditure of funds authorized to be appropriated for or otherwise available to the Department of Defense for FY2017 "to transfer or facilitate the transfer" of MANPADS to any entity in Syria.109 The Senate-passed versions of the FY2017 defense authorization (S. 2943) and the FY2017 defense appropriation (S. 3000) did not contain similar provisions.

Section 1224 of the FY2017 NDAA provides that funds available to the Department of Defense for FY2017 may not be used to provide MANPADS to vetted Syrian opposition forces until the Secretary of Defense and the Secretary of State jointly submit a report on the determination and 30 days elapse after the date of the report submittal. The House-engrossed version of the FY2018 NDAA would endorse these limits and terms for FY2018. In the 115th Congress, the FY2017 Consolidated Appropriations Act (§9013 of Division C of P.L. 115-31) prohibits the use of funds made available by the act for the Counter-ISIL Train and Equip Fund to procure or transfer MANPADs.

In 2016, some media reports suggested that non-U.S. entities sought to provide MANPADS to entities in Syria as a means of responding to escalating violence against opposition-held areas and empowering certain anti-Asad forces to defend themselves and Syrian civilians from air assaults by Syrian government and Russian air forces.110 Responding to questions about the potential provision of MANPADS to Syrian rebels by Gulf states, State Department Deputy Spokesman Mark Toner stated, "We cannot dictate what other countries—and I'm not naming names—... may or may not decide to do in terms of supporting certain groups within Syria."111 Press reports since 2012 have documented the appearance of MANPADS in limited numbers among some Syrian armed groups.112

Other Reported U.S. Assistance

Then-Secretary of Defense Chuck Hagel said in a September 2013 hearing before the Senate Foreign Relations Committee that the Obama Administration was taking steps to provide arms to some Syrian rebels under covert action authorities.113 Several press accounts citing unnamed U.S. government sources subsequently described details of reported U.S. and partner nation efforts to that effect.114 To date, other U.S. officials have not publicly acknowledged any such efforts or publicly described which elements of the Syrian opposition may have received U.S. training or support via any such channels, what any training may have entailed, what types of weaponry may have been provided, or what safeguards may be in place to monitor the disposition of equipment and the actions of any U.S.-trained or equipped personnel. One June 2015 article discussed differences of opinion among Members of Congress about future funding for the reported program.115 In October 2015, unnamed U.S. officials were cited in press reports that suggested that Russia was actively targeting Syrian opposition groups that had received covert support from the United States.116

U.S.-Origin Weaponry and the Syria Conflict

From 2014 onward, various anti-Asad forces released videos of their operatives loading and firing what appeared to be U.S.-origin antitank weaponry in Syria.117 In April 2014, an official affiliated with the now-defunct opposition group Harakat Hazm told the New York Times that "friendly states" had provided "modest numbers" of the weapons.118 The commander of the group told the Washington Post that those who supplied the missiles had U.S. government approval and said the shipment suggested "a change in the U.S. attitude toward allowing Syria's friends to support the Syrian people."119

Asked in April 2014 about the reported shipments and use of U.S. origin weaponry by Syrian rebels, U.S. National Security Council spokeswoman Bernadette Meehan said, "The United States is committed to building the capacity of the moderate opposition, including through the provision of assistance to vetted members of the moderate armed opposition. As we have consistently said, we are not going to detail every single type of our assistance."120 In May 2014, an unnamed senior Administration official reiterated that formulation to members of the press in a background briefing, while stating that "asymmetry which exists on the ground militarily, unfortunately, between the regime and the moderate opposition is problematic for the emergence of the kinds of political conditions necessary for a serious political process. And we and others are focused on that."121

Specific public information is lacking about the sources of U.S.-origin weaponry and which units or personnel may have continuing access to U.S.-origin weaponry.122 In 2015, a range of opposition groups largely affiliated with the Free Syrian Army movement published videos that purported to depict their personnel firing U.S.-origin antitank weapons. This includes groups targeted by Russian air strikes, some of whom have subsequently posted footage of their fighters using such weaponry to repel follow-on ground attacks by pro-Asad forces.123 Islamist groups also have posted similar videos and images of captured U.S.-origin antitank weapon stocks, including the Ansar al Islam Front,124 Jabhat al Nusra,125 and the Islamic State.126

In June 2016, a joint investigation by the New York Times and Al Jazeera concluded that weapons shipped into Jordan by U.S. and Saudi intelligence services intended for Syrian rebels were instead diverted by Jordanian intelligence officials and sold on the black market.127

Chemical Weapons and Disarmament128

A major policy concern of the United States has been the use of chemical weapons in Syria during the ongoing civil war. The reported use of the nerve agent sarin by aerial bombardment on April 4, 2017, in the town of Khan Sheikhoun in rebel-held Idlib province killed an estimated 80 to 100 people and returned the issue of chemical weapons in Syria to center stage. Secretary of State Tillerson said that the U.S. government had a "very high level of confidence" that the Syrian air force had used the nerve agent sarin in three recent attacks—on March 25, March 30, and April 4.129 In testimony to the Senate Select Committee on Intelligence on May 11, Director of National Intelligence Daniel Coats said that Syria was probably "willing and able" to use chemical weapons again.130 The U.S. Ambassador to the OPCW, Kenneth Ward said on October 10 that, "Syria has produced and continues to possess stocks of nerve agent and its immediate precursor chemicals."131

On April 6, the United States responded with missile strikes against Al Shayrat air base, which Pentagon officials stated is used to store chemical weapons.132 President Trump said that "It is in the vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons."133 Secretary of State Rex Tillerson also said the U.S. strike was aimed at reestablishing the norm against chemical weapons use:

As Assad has continued to use chemical weapons in these attacks with no response—no response from the international community—that he, in effect, is normalizing the use of chemical weapons, which may then be adopted by others. So it's important that some action be taken on behalf of the international community to make clear that the use of chemical weapons continues to be a violation of international norms.134

The World Health Organization said on April 5 that it was alarmed by the use of chemicals in Syria the previous day.135 The Turkish Ministry of Health said on April 6 that it had assessed that victims of the attack were exposed to sarin.136 The Organization for the Prohibition of Chemical Weapons (OPCW) began a Fact-Finding Mission on April 5 to investigate the event, and its inspectors collected samples which were sent to predesignated laboratories. The OPCW Director General said on April 19 that four of its laboratories had "incontrovertible" evidence that sarin or a sarin-like agent was used on April 4:

The bio-medical samples collected from three victims during their autopsy were analysed at two OPCW designated laboratories. The results of the analysis indicate that the victims were exposed to Sarin or a Sarin-like substance. Bio-medical samples from seven individuals undergoing treatment at hospitals were also analysed in two other OPCW designated laboratories. Similarly, the results of these analyses indicate exposure to Sarin or a Sarin-like substance.137

There have been dozens of reports of chemical weapons use in the Syrian conflict over the past several years. The largest-scale use of chemical weapons in Syria to date was an August 21, 2013, nerve gas attack, which the U.S. government estimated killed over 1,400 people.138 In August 2013, the Obama Administration had threatened military action against Syria in response to alleged nerve gas attacks by Syrian government forces. As part of a diplomatic solution to the crisis based on a U.S.-Russian joint proposal, the Administration withdrew the threat of military force and Syria agreed to give up its chemical weapons and join the Chemical Weapons Convention (CWC). U.N. Security Council Resolution 2118 (2013) further mandated that Syria give up all its chemical weapons under Chapter VII provisions of the U.N. Charter.139

After joining the CWC, Syria declared that it possessed 1,308 metric tons of chemical warfare agents and precursor chemicals, including several hundred metric tons of the nerve agents sarin and VX, as well as mustard agent in ready-to-use form. The nerve agents were stored as two separate components that are combined before use, called precursor chemicals, a form that facilitated removal and destruction efforts. The international community oversaw the removal and destruction of the declared chemical weapons agents from Syria, and, as of January 4, 2016, all declared Category 1 and 2 chemicals had been neutralized.140

Verification of the destruction of chemical weapons facilities is still underway. As of September 2017, the OPCW had verified that 25 of the 27 declared chemical weapons production facilities (CWPFs) had been destroyed. The poor security situation had prevented the inspection of the two remaining stationary above-ground facilities.141 For years, the United States, the OPCW Director General and other governments have raised questions over whether Syria declared all of its chemical weapons stocks and facilities. Press reports, nongovernment experts, and U.S. officials have said that the Asad regime used undeclared stocks of nerve agent in the April 4 attack in violation of its commitments under the CWC.142 The Organization for the Prohibition of Chemical Weapons (OPCW) has not been able to verify the completeness of the declaration, part of Syria's obligations under the CWC. The OPCW's Declaration Assessment Team (DAT) continues to investigate "gaps, inconsistencies and discrepancies" through interviews and lab analysis of samples from site visits, but the cooperation of the Syrian government has been limited and little progress has been made according to OPCW Executive Council reports.143

Since the August 2013 attack, reports of chemical weapons use in Syria have consisted primarily of accusations of chlorine use in barrel bombs until the alleged sarin use in the spring of 2017.144 Reports of the use of chlorine gas as a chemical weapon began to surface in April 2014. The OPCW established a fact-finding mission to investigate these allegations. The use of chlorine as a weapon is banned under the Chemical Weapons Convention. Several governments—including the governments of Syria and the United States—have submitted allegations of chemical attacks to the U.N. Secretary-General and/or the OPCW.145 The United States, the United Nations,146 and others have assessed that the Syrian government has used chemical weapons repeatedly against opposition forces and civilians in the country. Expert teams affiliated with the U.N.-OPCW Joint Mission to Investigate Allegations of the Use of Chemical Weapons in the Syrian Arab Republic and the OPCW Fact-Finding Mission in Syria have investigated some of these allegations and have found evidence that in some cases confirms and in others suggests that chemical weapons and/or toxic chemicals have been used in attacks by the Syrian regime and by the Islamic State. Syrian civilians, opposition fighters, and military personnel have been targeted in alleged attacks.147

Earlier U.N. and OPCW investigations had not been tasked with assigning responsibility for alleged attacks but with identifying whether chemical weapons were used. However, on August 7, 2015, the U.N. Security Council unanimously adopted Resolution 2235, which established a new OPCW-U.N. Joint Investigative Mechanism (JIM) tasked with identifying "to the greatest extent feasible" those responsible for or involved in chemical attacks identified by the OPCW fact finding mission.148 In September 2015, the United Nations Security Council adopted the Secretary-General's proposal for the establishment of the OPCW-U.N. JIM, and the Secretary-General appointed Virginia Gamba of Argentina to head the independent three-member panel that leads the JIM.

While Resolution 2235 empowers the JIM to have access anywhere in Syria, the JIM's mission has been complicated by the security situation on the ground. The JIM initially investigated nine attacks alleged to have occurred between April 2014 and August 2015. Of these, three cases lacked sufficient evidence to draw conclusions, three cases require further investigation, and three cases were concluded. Eight of the cases involved chlorine-filled barrel bombs. The JIM reports attributed four cases of chemical weapons use.149 According to the October 2016 report

An additional report is expected in the near future. The Security Council extended the mandate of the JIM through November 2017 despite initial objections by Russia, who argues for a wider regional mandate.151 The JIM's mandate remains limited to investigating alleged incidents of chemical weapons use in Syria, but will also include outreach to the UNSC's nonproliferation committee and neighboring states regarding nonstate use of chemical weapons. In the past, the United States has worked to extend the JIM, in order to "send a clear message that the use of chemical weapons will not be tolerated."152 It is unclear at this time whether the JIM's mandate will be renewed.

The Syrian government continues to deny categorically that it has used chemical weapons or toxic chemicals, while accusing opposition forces of doing so and calling into question the methods and results of some investigations into alleged chemical attacks.153 The Russian Federation supports the Syrian position. The U.N. representatives of the United States, France, and the United Kingdom continue to assert that the Syrian government has been conducting chemical attacks. An effort in February 2017 to pass a Security Council Resolution that would sanction Syria failed to get the votes of Russia or China.154 The latest incidence of use on April 4 elevated these issues again to the U.N. Security Council, where Russia defends the Syrian stance. The United States, United Kingdom, and France proposed a U.N. Security Council Resolution in support of a U.N. investigation into who was responsible for the April 4 attack, but this resolution was vetoed by Russia. Nevertheless, the U.N. and OPCW mechanisms already in place from past Security Council resolutions, the Fact Finding Mission (FFM) and the Joint Investigative Mechanism (JIM), investigated the April 4 attack. The FFM concluded that the April 4 attack used sarin. Another UN body, the Independent International Commission of Inquiry on the Syrian Arab Republic, issued a report attributing sarin use on April 4 to the Syrian military.

Additional press reports have reported on possible use of mustard gas in Syria and Iraq by IS fighters.155 The OPCW's chief has said that the Islamic State has produced and used sulfur mustard in northern Iraq and Syria.156 U.S. forces struck Islamic State sites in Iraq believed to be associated with chemical weapons production in September 2016, and a multilateral effort removed chemical weapons precursors from Libya in August 2016 after Islamic State affiliate forces threatened the area where the materials had been stored in that country. The Pentagon has said that U.S. troops fighting in Iraq are expected to continue to face weaponized mustard gas attacks by the Islamic State.157 April 2017 press reports said that the Islamic State had used chemical weapons against Iraqi forces in Mosul.158


Following the April chemical weapons attack, President Trump and the Administration expressed increased concern about Syrian President Bashar al Asad and skepticism regarding the legitimacy of his continued rule. Speaking on April 7, U.S. Permanent Representative to the United Nations Ambassador Nikki Haley spoke of "a new phase" and "a drive toward a political solution," following Secretary of State Tillerson's outline of U.S. goals for Syria on April 6.159 That outline prioritizes action against the Islamic State in pursuit of a political solution "that ultimately, in our view, will lead to a resolution of Bashar al Asad's departure."160 Since then, the Trump Administration has referred to efforts to deescalate the underlying conflict amid its continuing emphasis on counterterrorism.

Asad and Russia continue to reject calls for what they describe as Western-led regime change in Syria, and argue that counterterrorism cooperation with the Syrian government against its adversaries should precede further discussion of transition arrangements. Efforts to forcefully compel Asad's departure or empower opposition groups to depose Asad may risk direct confrontation with Russian military forces, with potentially broad implications beyond Syria. At the same time, the risk remains that any perceived U.S. acquiescence to or cooperation with Russia's intervention on Asad's behalf risks alienating anti-Asad forces and their regional backers, as well as providing Russia with an opportunity to consolidate a new, active role for itself in regional security arrangements.

Over the longer term, Syria's diversity and the interplay of its conflict and regional sectarian rivalries raise the prospect of continued violence even in the wake of the type of "managed transition" that has at times been identified as a U.S. policy goal. The presence and power in Syria of armed groups directly opposed to the governance models promoted by many Syrians and the United States suggests that the conflict could persist after any negotiated settlement seeking to replace the current Asad-led government with a government of national unity or other inclusive formulation. Political opposition coalitions active internationally appear to lack grassroots support and, because of their lack of material control over the most powerful armed groups, they appear to lack the ability to guarantee security commitments that might presumably be part of a negotiated settlement. Some analysts doubt the Asad government could survive a partial transition and suggest state collapse could accompany efforts to replace it whether by negotiation or by force. Even under relatively favorable circumstances, state weakness may allow extremist and terrorist groups to operate from Syria for years to come.

Observers, U.S. officials, and Members of Congress continue to differ over which incentives and disincentives may prove most effective in influencing combatants and their supporters. Still less defined are the long-term commitments that the United States and others may be willing to make to achieve an inclusive political transition acceptable to Syrians; protect civilians; defend U.S. partners; promote accountability and reconciliation; or contribute to the rebuilding of a country destroyed by years of brutal war.

Author Contact Information

[author name scrubbed], Coordinator, Analyst in Middle Eastern Affairs ([email address scrubbed], [phone number scrubbed])
[author name scrubbed], Specialist in Middle Eastern Affairs ([email address scrubbed], [phone number scrubbed])
[author name scrubbed], Specialist in Nonproliferation ([email address scrubbed], [phone number scrubbed])



Prepared by Matthew Weed, Specialist in Foreign Policy Legislation.


The letter says the strikes were intended "to degrade the Syrian military's ability to conduct further chemical weapons attacks and to dissuade the Syrian regime from using or proliferating chemical weapons, thereby promoting the stability of the region and averting a worsening of the region's current humanitarian catastrophe."


"Terrorist Designations of the al-Nusrah Front as an Alias for al-Qa'ida in Iraq," Press Statement by State Department Spokesperson Victoria Nuland, December 11, 2012.


President Barack Obama, Remarks by the President to the White House Press Corps, August 20, 2012.


Action Group for Syria, Final Communiqué, June 30, 2012.


Letter dated 22 March 2013 from the Secretary-General addressed to the President of the Security Council, U.N. Document S/2013/184, March 22, 2013.


The White House, Government Assessment of the Syrian Government's Use of Chemical Weapons on August 21, 2013, August 30, 2013. United Nations investigations confirmed that a chemical attack took place but its September and December 2013 reports did not address attribution. See U.N. Document A/67/997–S/2013/553, Report of the United Nations Mission to Investigate Allegations of the Use of Chemical Weapons in the Syrian Arab Republic on the alleged use of chemical weapons in the Ghouta area of Damascus on 21 August 2013, September 16, 2013; and, United Nations Mission to Investigate Allegations of the Use of Chemical Weapons in the Syrian Arab Republic, Final Report, December 2013.


President Barack Obama, Remarks by the President Before Meeting with Members of Congress on the Situation in Syria, September 3, 2013.


The FY2015 Continuing Resolution (P.L. 113-164, "the FY2015 CR") contained temporary authorization for the training and equipping of vetted Syrians that differed from the Administration's requests and expired on December 11, 2014. The FY2015 NDAA (Sections 1209, 1510, and 1534 of Division A of P.L. 113-291) and the Consolidated and Further Continuing Appropriations Act, 2015 ("Counterterrorism Partnership Fund" and Section 9016 of P.L. 113-235) provided further authority and funding guidance for the program.


President Trump Statement on Syria, April 6, 2017; and, Statement from Pentagon Spokesman Capt. Jeff Davis on U.S. strike in Syria, Release No: NR-126-17, April 6, 2017.


Statement by Secretary of Defense Jim Mattis on the U.S. Military Response to the Syrian Government's Use of Chemical Weapons, April 10, 2017; Press Conference by Secretary Mattis and Gen. Votel in the Pentagon Briefing Room, April 11, 2017.


"Russians Strike Targets in Syria, but Not ISIS Areas," New York Times, September 30, 2015.


"Russia's attack on U.S.-backed rebels in Syria puzzles, frustrates the Pentagon," Military Times, June 23, 2016.


"Russia says general killed in Syria held senior post in Assad's army," Reuters, September 27, 2017.


"Putin signs Syria base deal, cementing Russia's presence there for half a century," Reuters, July 27, 2017.


Department of Defense Press Briefing by General Townsend via teleconference from Baghdad, August 31, 2017.


Department of Defense Press Briefing by General Townsend via teleconference from Baghdad, August 31, 2017.


Media Availability with Secretary of Defense Jim Mattis; Brett McGurk, Special Presidential Envoy for the Global Coalition to Counter the Islamic State of Iraq and the Levant, August 21, 2017.


Media Availability with Secretary of Defense Jim Mattis; Brett McGurk, Special Presidential Envoy for the Global Coalition to Counter the Islamic State of Iraq and the Levant, August 21, 2017.


"Jets strike U.S.-backed forces in eastern Syria," Reuters, September 16, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, September 21, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, September 28, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, September 28, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, September 28, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, September 28, 2017.


Lieutenant General Stephen Townsend, commander, Combined Joint Task Force-Operation Inherent Resolve; Major Adrian Rankine-Galloway, Pentagon Spokesman, August 31, 2017




See, for example, "Syrian Opposition Figure to Deploy All-Arab Force in Raqqa Offensive," Reuters, February 1, 2017.


Department of Defense Briefing by Gen. Townsend via Telephone from Baghdad, Iraq, March 28, 2017; Amberin Zaman, "Tillerson Leaves Ankara with No New Enemies—or Friends," Al-Monitor Turkey Pulse, March 30, 2017; Suleiman Al-Khalidi, "U.S.-Backed Forces Repel Islamic State Attack near Syrian Dam," Reuters, April 2, 2017.


Aaron Stein and Michelle Foley, "The YPG-PKK Connection," Atlantic Council, January 26, 2016; "Ankara Intensifies Strikes Against YPG, Moves to Arrest PYD Leader," Al Monitor Turkey Pulse, November 22, 2016.


In an April 28, 2016, Senate hearing, Secretary of Defense Ash Carter appeared to answer "yes" to a question on whether the YPG has ties to the PKK, but he later reiterated that the YPG is not a designated terrorist organization.


Stein and Foley, op. cit. One source claims that although the PYD and PKK are officially independent, "in practice, Syrian Kurdish PKK cadres with years of service in Qandil (the organisation's northern Iraqi mountain base) dominate the YPG leadership and are the decision-makers within the self-proclaimed 'autonomous administration'" in Syria.


Pentagon statement quoted in Michael R. Gordon, "Trump to Arm Syrian Kurds, Even as Turkey Strongly Objects," New York Times, May 9, 2017. For information on U.S. authorities to train and equip select armed Syrian groups to fight the Islamic State, see CRS Report R43612, The Islamic State and U.S. Policy, by [author name scrubbed] and [author name scrubbed]. One report said that the Pentagon plan would provide YPG forces with "small arms, ammunition and machine guns." "U.S., Turkey Boost Antiterror Cooperation," Wall Street Journal, May 11, 2017. Another said that weapons would include "heavy machine guns, mortars, anti-tank weapons, armored cars and engineering equipment." "Trump to Arm Syrian Kurds, Even as Turkey Strongly Objects," New York Times, May 9, 2017.


"Turkey Assails U.S. Decision to Arm Syrian Kurds," New York Times, May 11, 2017.


"Turkey furious at US decision to arm Syrian Kurdish group," Hurriyet Daily News, May 10, 2017; "Anti-terror fight should not be carried out with other terror groups: Erdoğan," Hurriyet Daily News, May 10, 2017.


Amberin Zaman, "Mattis pledges Erdogan US support against PKK," Al-Monitor Turkey Pulse, August 23, 2017.


Department of Defense Press Briefing by Col. Dorrian via teleconference from Baghdad, Iraq, February 22, 2017.


Shawn Snow, "Syrian Kurds are now armed with sensitive US weaponry, and the Pentagon denies supplying it," Military Times, May 7, 2017.


Remarks by Secretary Carter at the 2016 IISS Manama Dialogue, Manama, Bahrain, December 10, 2016.


Department of Defense Press Briefing by General Townsend via teleconference from Baghdad, Iraq, August 31, 2017.


"U.S. Is Sending 400 More Troops to Syria," New York Times, March 9, 2017.


Department of Defense Press Briefing by Col. Dorrian via teleconference from Baghdad, Iraq, March 15, 2017.


Department of Defense Briefing by Gen. Townsend via Telephone from Baghdad, Iraq, March 28, 2017.


"Syria army breaks years-long siege of Deir Ezzor airbase," AFP, September 10, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, Iraq, September 14, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, Iraq, September 14, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, Iraq, September 21, 2017.


Department of Defense Press Briefing by Col. Dillon via teleconference from Baghdad, Iraq, September 28, 2017.


Department of Defense Press Briefing by Col. Dillon via teleconference from Baghdad, Iraq, September 14, 2017.


Department of Defense Press Briefing by Pentagon Chief Spokesperson Dana W. White and Joint Staff Director Lt. Gen. Kenneth F. McKenzie Jr. in the Pentagon Briefing Room, October 5, 2017.


"Syrian rebels seize Iraq border crossing from Islamic State: monitor," Reuters, March 4, 2016.


Department of Defense Press Briefing by Col. Dillon via teleconference from Baghdad, Iraq, June 1, 2017.


Department of Defense Press Briefing by Col. Dorrian via teleconference from Baghdad, Iraq, April 12, 2017.


Department of Defense Press Briefing by Col. Garver via Teleconference From Baghdad, Iraq, July 6, 2016.


Department of Defense Press Briefing by Col. Dorrian via teleconference from Baghdad, Iraq, May 3, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, Iraq, July 27, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, Iraq, August 3, 2017.


On May 24, Combined Forces Air Component Commander Lieutenant General Jeffrey Harrington acknowledged the existence of a 55-kilometer deconfliction zone around At Tanf, stating "if the Russians are going to come in there, they're going to call us to give us information about what they would like to do, and we're going to have a discussion about it."


Coalition Defends Partner Forces From Syrian Fighter Jet Attack, Release No: 17-228 June 18, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, Iraq, September 21, 2017.


"Along Syria-Jordan Border, Refugees Struggle At A Camp Aid Workers Can't Visit," NPR, March 20, 2017.


UNHCR, Jordan Operational Update, August 2017.


UNOCHA, Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator, Stephen O'Brien, Statement to the Security Council on Syria, August 30, 2017.


Sam Heller, "Desert Base Is Displaced Syrians' Last Line of Defense," The Century Foundation, September 8, 2017.


Department of Defense Press Briefing by Col. Dorrian via teleconference from Baghdad, Iraq, March 15, 2017.


Department of Defense Press Briefing by Col. Dorrian via teleconference from Baghdad, Iraq, March 15, 2017.


Department of Defense Press Briefing by Col. Dorrian via teleconference from Baghdad, Iraq, March 15, 2017.


Department of Defense Press Briefing by Colonel Dillon via teleconference from Baghdad, Iraq, August 10, 2017.


Department of Defense Press Briefing by General Townsend via teleconference from Baghdad, Iraq, August 31, 2017.


Amberin Zaman, "Turkish Troops Enter Syria to Fight ISIS, May Also Target U.S.-Backed Kurdish Militia," Woodrow Wilson Center, August 24, 2016.


"Turkey Can Start New Operation If Necessary as Euphrates Shield Ends: PM," Hurriyet Daily News, March 30, 2017.


"Turkish jets strike Kurdish fighters in Syria, Iraq's Sinjar," Reuters, April 25, 2017.


State Department Press Briefing, April 25, 2017.




State Department Press Briefing, April 25, 2017.


"Turkey warns new military moves in Syria imminent," Washington Post, August 5, 2017; "After military shake-up, Erdogan says Turkey to tackle Kurds in Syria," Reuters, August 7, 2017.


"Turkey's president announces operation in Syria's Idlib," The Washington Post, October 7, 2017.


"Turkey backs Syrian rebels for 'serious operation' in Idlib," Reuters, October 7, 2017.




"Turkish troops enter Syria in a major operation to support anti-Assad rebels," Independent, October 9, 2017.


Action Group for Syria, Final Communiqué, June 30, 2012,


"Syrian President Bashar al-Assad Wins Third Term," BBC, June 5, 2014.


State Department, "On-the-Record Briefing With Acting Assistant Secretary for Near Eastern Affairs David Satterfield on Syria," September 18, 2017.


State Department Daily Press Briefing, December 20, 2016.


Statement on establishing the cease-fire regime in the Syrian Arab Republic, contained in Annex I to U.N. Document S/2016/1133, December 29, 2016.


Joint statement by Iran, Russia and Turkey on the International Meeting on Syria in Astana 14-15 September 2017, Russian Ministry of Foreign Affairs, September 18, 2017.


"New escalated violations witnessed by the 'de-escalation zones' with the end of the 7th day of the ceasefire agreement," Syrian Observatory for Human Rights, May 13, 2017.


"Syrian opposition HNC group criticizes de-escalation deal," Reuters, May 5, 2017.


U.S. Department of State, "Statement on Russia, Turkey, and Iran's De-Escalation Zones Plan for Syria," May 4, 2017.


"Syria: Turkey, Russia, Iran Agree to Safe Zone Deal," VOA News, September 15, 2017.


"Tehran, Ankara and Moscow Reach Agreement over Syria's Idlib," Middle East Institute, September 15, 2017.


"U.S. Dismisses Russia's Ban on Aircraft Over Syrian Safe Zones," Wall Street Journal, May 5, 2017.


State Department Bureau of Population, Refugees, and Migration, U.S. Humanitarian Assistance in Response to the Syrian Crisis, April 5, 2017. See also USAID, Syria–Complex Emergency, Fact Sheet #4, Fiscal Year (FY) 2017, April 27, 2017.


State Department Fact Sheet, "U.S. Humanitarian Assistance in Response to the Syrian Crisis," September 21, 2017.


The Consolidated Appropriations Act, 2017 provides funding to several global humanitarian accounts, including $3.058 billion to the Migration and Refugee Assistance (MRA) account and $3.811 billion to the International Disaster Assistance (IDA) account, some of which will be used to respond to the Iraq-Syria crises.


For additional details, see UNDP and UNHCR, 3RP Regional Refugee & Resilience Plan 2017 – 2018: In Response to the Syria Crisis: Regional Strategic Overview, December 5, 2016.


For additional details, see UNOCHA, 2017 Syrian Arab Republic Humanitarian Response Plan: January - December 2017.


Secretary of State Rex Tillerson, Remarks with National Security Advisor H.R. McMaster, April 6, 2017.


Briefing by Brett McGurk, Special Presidential Envoy for the Global Coalition To Counter ISIS, Office of the Special Presidential Envoy for the Global Coalition To Counter ISIS, August 4, 2017.


President George W. Bush included this formulation in 10 signing statements from 2003 to 2006.


Office of the State Department Spokesperson, "Syrian Crisis: U.S. Efforts and Assistance," August 7, 2015.


Opposition infighting in late 2013 led to the capture of some nonlethal U.S. assistance by Islamist groups. U.S. officials subsequently revisited some delivery and monitoring mechanisms and worked to improve the reliability and security of delivery channels. Dasha Afanasieva and Humeyra Pamuk, "U.S., Britain suspend aid to north Syria after Islamists seize weapons store," Reuters, December 11, 2013.


Syria Humanitarian Assistance, Government Accountability Office, July 2016.


For background on the origins of this program and related legislation, see CRS Report R43727, Train and Equip Program for Syria: Authorities, Funding, and Issues for Congress, by [author name scrubbed] and [author name scrubbed].


The program came under intense scrutiny in the wake of August and September 2015 reports that some of the small number of U.S. trainees that had completed the program quit and others may have turned over equipment and weaponry to Jabhat al Nusra, the Al Qaeda affiliate that controls much of Idlib Province in northwest Syria. As of October 2015, U.S. officials reported that the program had produced 124 graduates, 70 of whom had returned to Syria in September 2015. Of the other 54, U.S. CENTCOM Commander General Lloyd Austin told the Senate Armed Services Committee that "four or five" then remained "in the fight" against the Islamic State in Syria, after having come under Jabhat al Nusra attack in July 2015.


Prior approval reprogramming request notifications can be reviewed on the website of the Office of the Under Secretary of Defense (Comptroller) under Budget Execution materials for corresponding fiscal years.


In June 2014, the House adopted H.Amdt. 914 to H.R. 4870, which provided that "None of the funds made available by this Act may be obligated or expended to transfer man-portable air defense systems (MANPADS) to any entity in Syria." It was included in the House engrossed version of the bill as Section 10010.


H.Amdt. 487 to H.R. 2685.


See Amendment 81 in H.Rept. 114-571, adopted as part of en bloc amendment H.Amdt. 1046 to H.R. 4909. If enacted, the amendment would provide that, "none of the funds authorized to be appropriated by this Act or otherwise made available for the Department of Defense for fiscal year 2017 may be obligated or expended to transfer or facilitate the transfer of man-portable air defense systems (MANPADS) to any entity in Syria."


Jonathan Landay and Arshad Mohammed, "Gulf may arm rebels now Syria truce is dead - U.S. officials," September 27, 2016.


State Department press briefing by Deputy Spokesperson Mark C. Toner, September 27, 2016.


"Syrian Rebels Get Missiles," Wall Street Journal, October 17, 2012; "Officials: Syrian rebels' arsenal includes up to 40 antiaircraft missile systems," Washington Post, November 28, 2012; "As Russian planes bombard Syrian rebels, debate over anti-aircraft missiles returns," Los Angeles Times, May 1, 2016.


Secretary Hagel said, "it was June of this year that the president made the decision to support lethal assistance to the opposition. As you all know, we have been very supportive with hundreds of millions of dollars of nonlethal assistance. The vetting process that Secretary Kerry noted has been significant, but—I'll ask General Dempsey if he wants to add anything—but we, the Department of Defense, have not been directly involved in this. This is, as you know, a covert action. And, as Secretary Kerry noted, probably to [go] into much more detail would—would require a closed or classified hearing."


Adam Entous, Julian E. Barnes and Siobhan Gorman, "U.S. Begins Shipping Arms for Syrian Rebels," Wall Street Journal, June 26, 2013; Greg Miller, "CIA ramping up covert training program for moderate Syrian rebels," Washington Post, October 2, 2013; Greg Miller and Karen DeYoung, "Secret CIA effort in Syria faces large funding cut," Washington Post, June 12, 2015.


Miller and DeYoung, "Secret CIA effort in Syria faces large funding cut," Washington Post, June 12, 2015.


Adam Entous, "U.S. Sees Russian Drive Against CIA-Backed Rebels in Syria," Wall Street Journal, October 5, 2015.


See Harakat Hazm YouTube Channel, April 15, 2014, at


Ben Hubbard, "Syrian Election Announced; Rebels Report New Weapons," New York Times, April 21, 2014.


Liz Sly, "Syrian rebels who received first U.S. missiles of war see shipment as 'an important first step,'" Washington Post, April 27, 2014.


Tom Bowman and Alice Fordham, "CIA Is Quietly Ramping Up Aid To Syrian Rebels, Sources Say," National Public Radio (Online), April 23, 2014.


Transcript of Background Briefing on Syria by Senior Administration Official, U.S. State Department, May 5, 2014.


Section 3(a)(2) of the Arms Export Control Act (22 U.S.C. 2753 (a)(2)) applies obligations, restrictions, and possible penalties for misuse of U.S.-origin equipment to any retransfer by foreign recipients of U.S.-supplied defense articles, defense services, and related technical data to another nation. If such a retransfer occurred in the absence of prior U.S. approval, then the nation making such a transfer could be determined to be in violation of its agreement with the United States not to take such an action without prior consent from the U.S. government.


See Tajammu al Izza YouTube Channel, October 1, 2015, at


See Ansar al Islam Front YouTube Channel, August 10, 2014, at and


Umberto Bacchi, "Syria: al-Qaeda Nusra Front Shows Off Huge Cache of US Weapons Seized from Moderate Harakat Hazm Rebels," International Business Times, March 4, 2015; Michael Smallwood, "Captured TOW 2A Missiles Employed in Syria," Armament Research Services, 2015.


OSC Report TRR2015062676424947, ISIL Deploys Apparent TOW Missile System Against Regime Forces in Al Hasakah, June 26, 2015.


"C.I.A. Arms for Syrian Rebels Supplied Black Market, Officials Say," New York Times, June 26, 2016.


Prepared by Mary Beth Nikitin, Specialist in Nonproliferation. See also CRS Insight IN10771, Syria's Chemical Weapons: Continuing Challenges, by [author name scrubbed] and CRS Report R43612, The Islamic State and U.S. Policy, by [author name scrubbed] and [author name scrubbed].


The Syrian government in 2013 joined the Chemical Weapons Convention (CWC), which bans the use of any toxic chemicals in warfare and requires—along with U.N. Security Council resolutions—that Syria destroy all of its chemical weapons stocks and production facilities under international supervision.


Hearing on Worldwide Threats, Senate Select Committee on Intelligence, May 11, 2017.


Statement by Kenneth D. Ward, Permanent Representative of the United States of America to the OPCW, at the Eighty-Sixth Session of the Executive Council, October 20, 2007.


"Trump Orders Missile Attack in Retaliation for Syrian Chemical Strikes," DoD News, April 6, 2017.


Statement by President Trump on Syria, April 6, 2017.


Rex Tillerson, Secretary of State, Remarks with National Security Advior H.R. McMaster, April 6, 2017.


World Health Organization, "WHO Alarmed by Use of Highly Toxic Chemicals in Syria," press release, April 5, 2017.


Some victims of the attack were moved to Turkey for treatment, where experts could assess their symptoms and likely causes. Louisa Loveluck, "Deadly Nerve Agent Sarin Used in Deadly Attack," Washington Post, April 6, 2017.


"OPCW Director-General Shares Incontrovertible Laboratory Results Concluding Exposure to Sarin," OPCW Press Release, April 19, 2017.


White House Office of the Press Secretary, Government Assessment of the Syrian Government's Use of Chemical Weapons on August 21, 2013, August 30, 2013.


Chapter VII of the U.N. Charter authorizes the use of punitive measures such as sanctions or military force.


Organization for the Prohibition of Chemical Weapons, "Destruction of Syrian Chemical Weapons Completed," press release, January 4, 2016.


"Note by the Director General: Progress in the Elimination of the Syrian Chemical Weapons Programme," EC-86/DG.23, September 25, 2017.


Joint News Conference with Secretary Mattis and Minister of Defense Lieberman in Tel Aviv, Israel, Department of Defense News Transcript, April 21, 2017; Julian E. Barnes and Maria Abi-Habib, "Syrian Attack Defies 2013 Chemical-Weapons Deal," Wall Street Journal, April 6, 2017.




UN Commission of Inquiry Info Graphic: Chemical Weapons Attacks Documented by the U.N. Commission of Inquiry on the Syrian Arab Republic, as of September 6, 2017; Arms Control Association, "Timeline of Chemical Weapons Attacks in Syria: 2012-2017," fact sheet, 2017.


Reports by U.N. Member States have been made via confidential correspondence, such as letters containing allegations described generally in the December 2013 final report of U.N. Mission to Investigate Allegations of the Use of Chemical Weapons in the Syrian Arab Republic (the U.N. Mission). See U.N. Mission, Final Report, December 12, 2013, pp. 2-6.


The U.N. Mission to investigate Allegations of the Use of Chemical Weapons in the Syrian Arab Republic released its report on September 16, 2013, concluding that surface-to-surface rockets containing the chemical weapons nerve agent sarin were used in the Ghouta area of Damascus against civilians on a "relatively large scale." The 2013 U.N. investigative mission was not tasked with assigning culpability for the attacks.


See U.N. Mission, Final Report, December 12, 2013; and OPCW Fact-Finding Mission (FFM) in Syria, Final Report, December 2015, attached to "Letter dated 27 January 2016 from the Secretary-General addressed to the President of the Security Council," S/2016/85, January 28, 2016.


Resolution 2235 required that the U.N. Secretary-General, in coordination with the OPCW Director-General, submit within 20 days recommendations for its approval on the establishment of a Joint Investigative Mechanism "to identify to the greatest extent feasible individuals, entities, groups, or governments who were perpetrators, organisers [sic], sponsors or otherwise involved in the use of chemicals as weapons, including chlorine or any other toxic chemical, in the Syrian Arab Republic where the OPCW FFM determines or has determined that a specific incident in the Syrian Arab Republic involved or likely involved the use of chemicals as weapons, including chlorine or any other toxic chemical…."


Letter dated 24 August 2016 from the Leadership Panel of the Organization for the Prohibition of Chemical Weapons-United Nations Joint Investigative Mechanism addressed to the Secretary-General, S/2016/738; Letter dated 21 October 2016 from the Leadership Panel of the Organization for the Prohibition of Chemical Weapons-United Nations Joint Investigative Mechanism addressed to the Secretary-General, S/2016/888.


The JIM report states that OPCW experts were able to identify that the sulfur mustard was produced by the Islamic State because of the way it was produced, which was different from Syrian government stocks. "The OPCW confirmed that the sulfur mustard from the Syrian Arab Republic did not contain impurities such as polysulphides, meaning that a different process was used by the Government. The OPCW also reported that the sulfur mustard used by ISIL in northern Iraq on several occasions in 2015 and 2016 was produced through the Levinstein process." Ibid, p. 97.


"Syria: Renewal of the UN-OPCW Joint Investigative Mechanism," What's In Blue, November 17, 2016.


Mark Toner, Deputy State Department Spokesman, "The Fourth Report of the Joint Investigative Mechanism," Press Statement, October 28, 2016.


On August 7, the Permanent Representative of Syria to the United Nations Dr. Bashar Jaafari told the United Nations Security Council that, "the Syrian Government and the Syrian army have never used chemical weapons, and never will. Contrariwise, Syria's army and its civilians have been targeted with toxic chemicals and chemical weapons, including chlorine gas, by armed terrorist groups, such as Daesh [Arabic acronym for ISIL] and the Al-Nusra Front, in many parts of Syria… ." He accused unspecified investigation missions of having "based their work on false, fabricated statements made by parties well known to all. Those missions have carried out partial and biased investigations—outside Syria—without a modicum of coordination with the Syrian authorities." (U.N. Document S/PV.7501.) The U.N. and OPCW investigative missions have worked inside Syria with the permission of the Syrian government. In 2011, the U.N. Human Rights Council established an Independent International Commission of Inquiry on the Syrian Arab Republic that has reported extensively on the conflict, including on alleged chemical attacks. The commission uses a "reasonable grounds to believe" standard of evidence and relies on first-hand accounts from Syrians now in neighboring countries, remote interviews, and other publicly available information.


"Syria Draft Resolution Imposing Sanctions Regarding the Use and Production of Chemical Weapons," What's In Blue, February 25, 2017.


"U.S. Tests Show Mustard Gas Traces in Islamic State Attack," The Washington Post, August 21, 2015.


Slovenia Press Agency, "IS Likely Used Chemical Weapons in Syria, Iraq; Could Use Them Elsewhere, OPCW Head Says," May 11, 2016.


"U.S.: Shell That Hit Iraqi Base Contained Sulfur-Mustard Agent," Associated Press, September 22, 2016; "U.S. Troops Brace for More Mustard Attacks," Military Times, September 27, 2016.


"ISIS Militants Launch Multiple Chemical Weapons Attacks on Iraqi Troops," Newsweek, April 17, 2017; "Chemical Attacks and Narrow Streets Complicate Fight for Mosul's Old City, "Al-Monitor, April 2017; "The Islamic State threatens more chemical attacks in Mosul after loss of senior ISIS commander," SOFREP News, April 20, 2017.


U.S. Permanent Representative to the United Nations Ambassador Nikki Haley, Remarks at a U.N. Security Council Meeting on the Situation in Syria, April 7, 2017.


Secretary of State Rex Tillerson, Remarks with National Security Advisor H.R. McMaster, April 6, 2017.