Updated December 16, 2022
Nuclear-Armed Sea-Launched Cruise Missile (SLCM-N)
In its FY2023 budget request, the Navy eliminated funding
Forces (INF) Treaty and provide Russia with an incentive
for research and development into a new nuclear-armed
to negotiate reductions in its nonstrategic nuclear weapons.
sea-launched cruise missile (SLCM-N). The Navy indicated
that the program was “cost prohibitive and the acquisition
SLCM-N was one of two systems that the 2018 NPR
identified as a way to “strengthen deterrence of regional
schedule would have delivered capability late to need.”
adversaries.”
According to the Navy, this cancellation would save $199.2
The Navy deployed a low-yield version (with
less than 10 kilotons, rather than 100 kilotons, of explosive
million in FY2023 and $2.1 billion over the next five years.
The Biden Administration’s 2022 Nuclear Posture Review
power) of the W76 warhead on its long-range submarine-
launched ballistic missile in 2019 (see CRS In Focus
(NPR) announces the SLCM-N program’s cancelation.
IF11143, A Low-Yield, Submarine-Launched Nuclear
Background
Warhead: Overview of the Expert Debate, by Amy F.
Woolf). The Navy conducted an Analysis of Alternatives in
The United States first deployed a nuclear-armed version of
support of the SLCM-N from 2019-2021, and expected to
the Tomahawk land-attack cruise missile (TLAM-N) in the
begin the development of the missile in 2022 and achieve
mid-1980s. The missiles were deployed on both surface
operational capability late in the 2020s.
ships and attack submarines. With a range of 2,500
kilometers (around 1,550 miles), the missiles were not
In its FY2022 budget request, the Biden Administration
considered part of the U.S. strategic nuclear forces (see
sought $5.2 million in DOD funding for research and
CRS In Focus IF10519, Defense Primer: Strategic Nuclear
development into the missile and $10 million for the
Forces, by Amy F. Woolf) and, therefore, did not count
National Nuclear Security Administration (NNSA) to work
under the limits on warheads or delivery vehicles in U.S.-
on a warhead that would be carried by the SLCM-N. At the
Soviet arms control agreements.
same time, the Administration indicated that it would
review the program as a part of its NPR.
In September 1991, at the end of the Cold War, President
George H.W. Bush announced that the United States would
After the Navy eliminated funding for SLCM-N in its
withdraw all land-based tactical nuclear weapons (those
FY2023 budget request, some Members of Congress asked
that could travel less than 300 miles) from overseas bases
General Milley, the Chairman of the Joint Chiefs of Staff,
and all sea-based tactical nuclear weapons from U.S.
and Secretary of Defense Austin whether they supported the
surface ships, submarines, and naval aircraft. The Navy
decision. General Milley said he continued to support
withdrew the TLAM-N missiles by mid-1992. It eliminated
SLCM-N because the President “deserves to have multiple
the nuclear mission for U.S. surface ships but could have
options to deal with national security situations.” But he
returned TLAM-N to attack submarines. Many viewed the
later noted that the United States has “lots of options and
U.S. ability to return these missiles to deployment on short
we have a significant nuclear capability.” Secretary Austin
notice as a part of the U.S. effort to reassure allies in Asia
also recognized the value of the SLCM-N but stated that
of the U.S. commitment to their security.
“the marginal capability that this provides is far outweighed
by the cost.”
In 2010, the Obama Administration’s NPR recommended
that the Navy retire the TLAM-N missiles. It indicated that
The 2022 NPR explains that the SLCM-N is “no longer
“this system serves a redundant purpose in the U.S. nuclear
necessary” because of the W76-2 low-yield SLBM
stockpile” as one of several weapons the United States
warhead’s “deterrence contribution.” Officials from the
could deploy in support of U.S. allies. It concluded that
Departments of Defense and State subsequently argued that
because “the deterrence and assurance roles of TLAM-N
the capabilities of the W-76-2, as well as other U.S. nuclear
can be adequately substituted by these other means,” the
weapons, obviate the need for the SLCM-N. The Biden
United States could continue to support allies in Asia
Administration’s October 2022 statement on the FY2023
without maintaining the capability to redeploy TLAM-N
National Defense Authorization Act (NDAA) asserts that
missiles. The Navy completed the retirement of these
continuing the SLCM-N program “would divert resources
missiles by 2013.
and focus from higher [U.S. nuclear] modernization
priorities.” The NDAA authorizes $25 million for continued
The Trump Administration, in effect, reversed this decision,
research and development for a SLCM-N.
noting in the 2018 NPR that a nuclear-armed sea-launched
cruise missile (now known as SLCM-N) would provide the
Issues in the SLCM-N Debate
United States with “a needed non-strategic regional
presence” that would address “the increasing need for
Deterrence Rationale
flexible and low-yield options.” This is intended to
According to a 2019 paper prepared by the Office of the
strengthen deterrence of regional adversaries and assure
Undersecretary of Defense for Policy, SLCM-N would
allies of the U.S. commitment to their defense. The NPR
serve as a response to developments in Russian and Chinese
also indicated that SLCM-N could serve as a response to
nuclear forces and doctrine that could undermine regional
Russia’s violation of the 1987 Intermediate-Range Nuclear
deterrence. The paper argued that the SLCM-N would be
“capable of proportional, discriminate response based on
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Nuclear-Armed Sea-Launched Cruise Missile (SLCM-N)
survivable, regionally present platforms, and with the
with a treaty-compliant response to Russia’s violation, but
necessary range, penetration capability, and effectiveness to
also noted that the United States “may reconsider the
hold critical adversary targets at risk.”
pursuit of a SLCM” if Russia “returns to compliance with
its arms control obligations, reduces its non-strategic
The SLCM-N would, the paper asserted, thus bolster
nuclear arsenal, and corrects its other destabilizing
deterrence by providing “additional limited employment
behaviors.”
capabilities that an adversary will have to consider if
contemplating the coercive use of nuclear weapons.” The
While many critics of SLCM-N have supported efforts to
paper argued that such capabilities would “give an
engage Russia in negotiations on its nonstrategic nuclear
adversary pause” and, if a crisis were to nonetheless
weapons, few of these experts believe that the SLCM-N
escalate, U.S. leaders would “have a wider range of options
could affect this process. Because the Navy would deploy
available in the event that the use of nuclear weapons is
the missile in the late 2020s, some argue its development
necessary to restore deterrence.” The paper also emphasized
would be unlikely to affect Russia’s arms control calculus
the benefits a sea-launched cruise missile could provide in
in the near term. In addition, the United States could be
reassuring U.S. allies, noting, “a regional nuclear presence
unwilling to trade the missile for Russian concessions, as
signals a high degree of resolve and readiness in a crisis,”
doing so would be inconsistent with the case made in the
and argued that “restoring that capability with SLCM-N
NPR that the SLCM-N was critical to bolstering U.S.
will bolster allied confidence in U.S. nuclear security
extended deterrence and assurance of allies in Europe and
guarantees.”
Asia.
Critics have argued that the capabilities highlighted by
Operational Concerns
advocates of SLCM-N deployment—regional presence,
Critics of the SLCM-N have questioned whether the
lower yield, and discriminate attack options—would lower
deployment of nuclear armed missiles on multipurpose
the threshold for nuclear use and increase the likelihood of
vessels might strain the Navy’s resources. The Navy would
nuclear war. They argue that by adding those capabilities to
likely have to adopt strict security protocols to protect the
its nuclear force posture, the United States would be
nuclear warheads, possibly diverting time and training
adopting a war-fighting posture rather than pursuing a
resources to maintain nuclear safety and surety standards.
doctrine based on deterrence.
The SLCM-N would also replace conventional missiles,
Some analysts outside government have also argued that the
thus limiting the numbers of conventional weapons
deployment of both nuclear-armed and conventional cruise
available for use in regional conflicts. Since the Navy has
missiles could create misperceptions and increase the risk
employed conventional cruise missiles in the past
of inadvertent nuclear war. Some have noted that nuclear
(including in retaliation for the use of chemical weapons in
and conventional SLCMs could be “virtually
Syria), they argue this could reduce the Navy’s ability to
indistinguishable” when launched and that this ambiguity
deter and respond to challenges in the future.
could “heighten the chance of miscalculation” and increase
Some have also questioned whether nuclear-armed SLCMs
the risk “that a state leader assumes an attack is nuclear and
could interfere with the Navy’s ability to operate in
retaliates with nuclear weapons.”
cooperation with U.S. allies. Several countries ban port
The 2019 paper refuted these concerns, noting the SLCM-N
calls from ships carrying nuclear weapons. Although the
did not “signal a shift toward a strategy emphasizing
U.S. Navy has long refused to confirm or deny the presence
nuclear warfighting or a lower threshold for nuclear
of nuclear weapons on specific naval vessels, it is
employment.” It was, instead, designed to “ensure that
commonly understood that the only U.S. Navy ships that
nuclear war is less rather than more likely by demonstrating
carry nuclear weapons are ballistic missile submarines. The
to adversaries that the United States is fully prepared to
presence of SLCM-N in the Navy could end the
deter nuclear threats at every stage of an escalating crisis or
presumption in the eyes of foreign countries that a visiting
conflict.” Moreover, some supporters have noted that the
Navy ship other than a ballistic missile submarine is not
United States has long employed conventional cruise
carrying nuclear weapons.
missiles in conflict—launched from both aircraft and naval
Supporters of the SLCM-N recognize that the missile could
vessels—without ever creating the misperception that the
affect Navy operations if they replace conventional
attack involved the use of nuclear weapons.
capabilities on Navy vessels. However, they dispute that the
missiles will necessarily detract from Navy operations. The
Arms Control Rationale
Pentagon’s 2019 report noted that DOD expected Navy
Several analysts and officials who support the SLCM-N
platforms to have “the capacity to deploy a large number of
have argued that its development could contribute to U.S.
cruise missiles, and that other naval platforms not assigned
arms control objectives by providing Russia with an
the SLCM-N mission will be able to deliver a significant
incentive to both reverse its development of a new land-
amount of conventional firepower.” The report concluded it
based cruise missile and negotiate limits on other types of
would be difficult to assess the specific tradeoffs between
shorter-range nonstrategic nuclear weapons. In this view,
nuclear and conventional weapons until the Navy
the SLCM-N would provide the United States with
conducted an evaluation of the deployment options for the
negotiating leverage that it lacks now, because it does not
SLCM-N, considering both the concept of operations and
possess any shorter-range nuclear missiles that it could
trade for limits on Russian or Chinese missiles.
the numbers of weapons that would be needed.
The 2018 NPR highlighted the potential arms control
This In Focus was originally authored by Amy F. Woolf,
benefits of the SLCM-N by linking it to U.S. concerns with
Specialist in Nuclear Weapons Policy.
Russia’s violation of the 1987 INF Treaty. Although the
United States has since withdrawn from the treaty, the NPR
Paul K. Kerr, Specialist in Nonproliferation
indicated the SLCM-N not only provided the United States
Mary Beth D. Nikitin, Specialist in Nonproliferation
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Nuclear-Armed Sea-Launched Cruise Missile (SLCM-N)

IF12084


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https://crsreports.congress.gov | IF12084 · VERSION 3 · UPDATED

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