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Updated May 31, 2024
Nuclear-Armed Sea-Launched Cruise Missile (SLCM-N)
Congress and the executive branch have debated the merits
SLBM in 2019. At the same time, the Navy conducted an
of a new nuclear-armed sea-launched cruise missile
Analysis of Alternatives on the SLCM-N.
(SLCM-N) since the weapon was first proposed by the
Trump Administration in 2018. The Biden Administration
In its FY2022 budget request, the Biden Administration
sought $5.2 million for Department of Defense (DOD)
proposed cancelling the SLCM-N program following its
2022 Nuclear Posture Review (NPR), a periodic assessment
research and development work on the SLCM-N. It also
requested $10 million for the National Nuclear Security
of U.S. nuclear policy. Congress has provided continued
funding for the SLCM-N and its warhead; the FY2024
Administration (NNSA) to study adapting the W80-4
nuclear warhead, intended for the Long-Range Standoff
National Defense Authorization Act (NDAA) requires the
executive branch to ensure SLCM-N initial operational
Weapon (LRSO) air-launched cruise missile, for delivery
carried by the SLCM-N. The Administration also stated that
capability (IOC). Since the FY2024 NDAA, the
Administration has taken steps to begin SLCM-N program
it would review the program in the 2022 NPR.
implementation.
The Biden Administration proposed cancelling the SLCM-
Background
N in the 2022 NPR, arguing that the missile was “no longer
necessary” because of the W76-2 SLBM warhead’s
The U.S. Navy first deployed a nuclear-armed sea-launched
“deterrence contribution.” The Navy’s FY2023 budget
cruise missile in the mid-1980s, when it placed the TLAM-
request eliminated funding for the SLCM-N, stating that the
N—a nuclear-armed version of the Tomahawk land-attack
missile was “cost prohibitive and the acquisition schedule
cruise missile—on surface ships and attack submarines.
would have delivered capability late to need.”
With a range of 2,500 kilometers (about 1,550 miles), the
missiles were not included in the limits in U.S.-Soviet arms
Current Status
control agreements.
The Biden Administration did not include the SLCM-N in
In 1991, at the end of the Cold War, President George H.W.
its FY2023, FY2024, or FY2025 budget requests. The
Bush announced that the United States would withdraw all
Administration’s policy statements on the FY2023 and
land-based tactical nuclear weapons (those that could travel
FY2024 NDAAs asserted that continuing the SLCM-N
less than 300 miles) from overseas bases and all sea-based
program “would divert resources and focus from higher
tactical nuclear weapons from surface ships, submarines,
modernization priorities.” Despite the Administration’s
and naval aircraft. The Navy withdrew the TLAM-N
objections, Congress has provided continued funding for
missiles by mid-1992 and eliminated the nuclear mission
the missile and the associated warhead (see Table 1).
for U.S. surface ships, but retained the option to return the
Table 1. Funding for SLCM-N
TLAM-N to attack submarines. Some observers
characterized this redeployment ability as demonstrating the
($ in millions)
credibility of U.S. defense commitments to allies in Asia.
Authorizations and
In 2010, the Obama Administration recommended that the
Appropriations
FY2023 FY2024
Navy retire the TLAM-N missiles. The 2010 NPR stated
Authorized for SLCM-N
25.0
190.0
that “this system serves a redundant purpose,” as it was one
of several weapons the United States could deploy in
Appropriated for SLCM-N
45.0
130.0
support of U.S. allies. The Navy completed the retirement
Authorized for SLCM-N warhead
20.0
70.0
of these missiles in 2013.
Appropriated for SLCM-N warhead
20.0
70.0
The Trump Administration reversed this decision, arguing
Source: P.L. 117-263; P.L. 118-31; P.L. 117-328; P.L. 118-47; P.L.
in the 2018 NPR that a nuclear-armed sea-launched cruise
118-42.
missile (now known as SLCM-N) would provide the United
States with a “non-strategic regional presence” that would
Section 1640 of the FY2024 NDAA (P.L. 118-31 of
address the “need for flexible and low-yield options.”
December 22, 2023) directs DOD to establish within 90
SLCM-N was one of two systems that the 2018 NPR
days a “major defense acquisition program” for the SLCM-
characterized as “modest supplements” that would
N under the Undersecretary of Defense for Acquisition and
“strengthen deterrence of regional adversaries” and assure
Sustainment (USD A&S), initiate a program to alter the
U.S. allies. The other 2018 NPR-recommended system was
W80-4 warhead for delivery via SLCM-N, and “ensure”
a low-yield version of the W76 nuclear warhead (known as
that the system achieves IOC no later than September 30,
the W76-2) for the Trident D5 long-range submarine-
2034. Section 1640 also mandates recurring DOD and
launched ballistic missile (SLBM). The 2018 NPR stated
NNSA briefings on SLCM-N program progress and a report
that the W76-2 was an option for the “near-term,” while
due in June 2024 on the “actions required to effectively
SLCM-N would be an option implemented over “the longer
term.”
deploy … [SLCM-N] from a Virginia class submarine and
The Navy deployed the W76-2 on the Trident D5
such other platforms as the Secretary [of the Navy]
determines appropriate,” as well as potential platform
https://crsreports.congress.gov
Nuclear-Armed Sea-Launched Cruise Missile (SLCM-N)
changes, modifications to port facilities, implications for
STRATCOM Commander General Anthony Cotton
manning, and associated costs.
reportedly wrote in 2023 that “a low-yield, non-ballistic
nuclear capability to deter, assure and respond without
While the Biden Administration did not include the SLCM-
visible generation” could provide the President with
N in its FY2025 budget request, USD A&S William
additional signaling and response options in a crisis. In
LaPlante testified in April 2024 that in March 2024 he had
April 2022 testimony, General Mark Milley, then-Chairman
directed the “Navy to establish a [SLCM-N] program office
of the Joint Chiefs of Staff, also expressed support for the
and to begin the analysis phase.” He also stated that the
SLCM-N, arguing that the President “deserves to have
Nuclear Weapons Council, a joint DOD-NNSA
multiple options.” The 2023 final consensus report of the
coordination group, is “leading a review of options to
Congressional Commission on the Strategic Posture of the
execute the SLCM-N program in a manner that balances
United States did not explicitly endorse the SLCM-N, but
cost, deterrence value, and risk to the [nuclear
called for a prompt system that is “forward deployed or
modernization] program of record and the Joint Force.”
deployable”; “survivable against preemptive attack without
Finally, he advocated balancing “SLCM-N programmatic
force generation day-to-day”; possesses “a range of
manning with on-going Navy and NNSA programs”
explosive yield options, including low yield”; and is able to
because they “draw from a limited pool of experienced
penetrate adversary integrated air and missile defenses.
government personnel and the same nuclear weapons
Observers have debated whether a nuclear posture that
industrial base and production enterprise.”
includes low-yield capabilities like the SLCM-N and the
Vice Admiral Johnny Wolfe, Director of the Navy’s
W76-2 and demonstrates a willingness to use nuclear
Strategic Plans and Programs, testified in April 2024 that
weapons improves deterrence or increases the risk of
funding appropriated for the SLCM-N in FY2023 “enabled
nuclear war. (See CRS In Focus IF11143, A Low-Yield,
initial development of a Concept of Operations” and other
Submarine-Launched Nuclear Warhead: Overview of the
activities to prepare for the first of three milestones in
Expert Debate.)
DOD’s acquisition process. Wolfe stated in a May 2024
hearing that the Navy had asked Congress for “flexibility”
Arms Control
to assess various options “that will give us that [SLCM-N]
Policymakers have debated the potential role of SLCM-N in
capability with minimum impact” on other Navy and
arms control. The 2018 NPR linked the missile to U.S.
NNSA modernization priorities.
concerns about a new missile that Russia has deployed in
violation of the 1987 Intermediate-Range Nuclear Forces
NNSA Administrator Jill Hruby testified in April 2024 that
(INF) Treaty. Although the United States withdrew from
NNSA had established a program office that has been
the treaty in 2018, the 2018 NPR stated that SLCM-N could
working with the Navy and also examining the W80-4 and
provide a treaty-compliant U.S. response to Russia’s
“potentially, other warheads that will be least disruptive” to
violation and incentivize Russia to engage in arms control
NNSA’s warhead programs. She stated in May 2024
negotiations concerning nonstrategic nuclear weapons. In
testimony that NNSA’s FY2025 unfunded priorities list
contrast, the 2022 NPR argued that there is “uncertainty
includes $70 million in funding for the SLCM-N warhead.
regarding whether SLCM-N on its own would provide
leverage” in such negotiations. Russia has rejected
Issues in the SLCM-N Debate
negotiations concerning its nonstrategic nuclear weapons,
citing these capabilities as necessary to offset to U.S. and
Deterrence Credibility and Flexibility of Options
NATO conventional superiority.
A key issue in the SLCM-N debate is whether adding the
missile to U.S. nuclear forces is necessary to credibly deter
Operational Tradeoffs and Costs
limited nuclear use by adversaries and assure allies in
The Biden Administration argued in a July 2023 policy
Europe and the Asia-Pacific that the United States would
statement that “deploying SLCM-N on Navy attack
protect them from nuclear coercion. The Biden
submarines or surface combatants would reduce capacity
Administration has stated that the United States has the
for conventional strike munitions, create additional burdens
ability in its “current and planned capabilities for deterring
on naval training, maintenance, and operations, and could
an adversary’s limited nuclear use through conventional
create additional risks to the Navy’s ability to operate in
and nuclear armaments,” including the W76-2 SLBM and
key regions.” In May 2024 testimony, Navy Secretary
air-delivered weapons such as the “Air-launched Cruise
Carlos Del Toro expressed concerns about the tactical and
Missile, its successor… [the LRSO], and F-35A dual-
operational tradeoffs and costs of SLCM-N for the Navy.
capable aircraft that can be equipped with B61-12 nuclear
gravity bombs.”
The 2022 NPR also cited the SLCM-N’s “estimated cost”
as a tradeoff. The Navy stated in 2022 that SLCM-N
SLCM-N proponents have argued that SLCM-N’s attributes
cancellation would save $199.2 million in FY2023 and $2.1
are different from low-yield capabilities delivered by other
billion over the next five years. Secretary of Defense Lloyd
means. They say that aircraft that deliver weapons would
Austin III testified in April 2022 that “the marginal
need to either be “generated” (fueled, weapons-loaded, and
capability that [the SLCM-N] provides is far outweighed by
flown) from the United States, which takes time, or else
the cost.” A July 2023 Congressional Budget Office (CBO)
placed in regional bases, where they could be vulnerable to
report estimated the costs of the SLCM-N and its warhead
adversary strikes. SLCM-N proponents also argue that
at $10 billion from 2023-2032 “if the program began in
deploying the missile on surface vessels or attack
2024.” This amount, the CBO noted, does not include
submarines provides advantages, such as greater
production costs beyond 2032, or cost for system
availability and regional presence, over deploying the W76-
integration, storage, or operations. SLCM-N supporters
2 SLBM on ballistic missile submarines.
argue that the deterrence and assurance benefits of SLCM-
N outweigh these operational tradeoffs and costs.
https://crsreports.congress.gov
Nuclear-Armed Sea-Launched Cruise Missile (SLCM-N)
This In Focus was originally authored by Amy F. Woolf,
Anya L. Fink, Analyst in U.S. Defense Policy
Specialist in Nuclear Weapons Policy.
IF12084
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https://crsreports.congress.gov | IF12084 · VERSION 4 · UPDATED