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

IF12084
Amy F. Woolf, Specialist in Nuclear Weapons Policy


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https://crsreports.congress.gov | IF12084 · VERSION 1 · NEW

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