Arms Control and International Security Papers 

Volume 11 Number 4 

Apri I 24, 2020 

Strengthening Deterrence 

and Reducing Nuclear 

Risks: The Supplemental 

Low-Yield U.S. SubmarineLaunched Warhead 

The Arms Control and International Security Papers are produced by the Office of the Under Secretary of State for Arms Control 

and International Security in order to make U.S. State Department policy analysis available in an electronically-accessible 

format compatible with "social distancing" during the COVID-19 crisis. 
Arms Control and International Security Papers 

Strengthening Deterrence and Reducing Nuclear Risks: The Supplemental 

Low-Yield U.S. Submarine-Launched Warhead 

Volume I, Number 4 I April 24, 2020 

Strengthening Deterrence and Reducing Nuclear 

Risks: The Supplemental Low-Yield U.S. 

Submarine-Launched Warhead 

This latest monograph in the Arms Control and International Security Paper 

Series - produced by the State Department's Bureau of Arms Control, 

Verification and Compliance, and with an introduction by Assistant Secretary 

Ford - explains U.S. thinking behind the supplemental low-yield W76-2 

Submarine-Launched Ballistic Missile (SLBM). 

Introduction: 

U.S. Nuclear Innovation for Deterrence 

The 2018 Nuclear Posture Review (NPR) outlined 

several ways in which the U.S. Government is working to 

meet its deterrence needs, and those of its Allies, through 

prudent and thoughtful answers to the challenges 

presented by the rapid deterioration of the global threat 

environment that has occurred since the publication of the 

previous NPR in 2010. Coming as it did at the outset of a 

period in which the United States was beginning to throw 

off a generation of post-Cold War complacency about 

great-power competition and explicitly to embrace 

competitive strategy in reaction to the provocations and 

military build-ups being undertaken by the Russian 

Federation and the People's Republic of China (PRC), the 

2018 NPR was a seminal document. It both highlighted 

some fundamental continuities in nuclear strategy that 

have been shared by successive U.S. administrations, and 

outlined modest innovations that had become necessary by 

these changing circumstances. 

Some of the innovations we announced in the NPR 

took effect immediately, such as the greater clarity we 

brought to U.S. declaratory policy by specifying that the 

"extreme circumstances" under which the United States 

does not a priori rule out the possibility of using nuclear 

weapons include the threat of "significant, non-nuclear 

strategic attacks" (SNNSAs). These attacks, the NPR made 

clear, "include, but are not limited to, attacks on the U.S., 

allied, or partner civilian population or infrastructure, and 

attacks on U.S. or allied nuclear forces, their command and 

control, or warning and attack assessment capabilities." 

This change did not expand the range of circumstances in 

which the United States might use nuclear weapons. 

Rather, it clarified the strategic nature of the adversary 

actions that might elicit an American nuclear response. We 

also made clear that we reserve the right to modify U.S. 

nuclear declaratory policy in any way "that may be 

warranted by the evolution and proliferation of non-nuclear 

strategic attack technologies and U.S. capabilities to 

counter that threat." 
Arms Control and International Security Papers 

Strengthening Deterrence and Reducing Nuclear Risks: The Supplemental 

Low-Yield U.S. Submarine-Launched Warhead 

Volume I, Number 4 I April 24, 2020 

This declaratory policy clarification was necessary 

because ours is an age in which non-nuclear capabilities 

have the potential to wreak havoc in some respects 

comparable to a nuclear attack, or to directly degrade the 

nuclear forces upon which we and our Allies rely in order to 

deter nuclear or large-scale conventional aggression. It is 

also, alas, an age in which both Russia and the PRC are 

developing just the sort of capabilities that such SNNSAs 

would require. To some extent, a commitment to deterring 

SNNSAs may have been de facto U.S. policy for many years 

under prior statements that the United States would only 

consider nuclear weapons use under "extreme 

circumstances." No previous U.S. administration, however, 

had been willing to offer any insight into what such 

longstanding comments about "extreme circumstances" 

actually meant. In a global environment of great power 

competition and accelerating threats in emergent 

battlespace domains, however, we opted for honesty and 

for clarity in order to enhance deterrence and reduce the 

risk of miscalculation. 

Some of the other innovations of the 2018 NPR will not 

materialize for some time. Our development and 

deployment of a "modern, nuclear-armed sea-launched 

cruise missile" as called for in the NPR, for instance - a 

capability needed to sustain deterrence in the face of 

modern threats by replacing the Tomahawk nuclearequipped, sea-launched cruise missile system that was 

unilaterally retired by the Obama administration -will take 

years. Our ongoing modernization of the legacy 

capabilities of the basic U.S. nuclear "Triad" of land-based 

missiles, heavy bombers, and sea-based ballistic missiles is 

now well underway, but it will also take years to complete. 

Other innovations in current U.S. nuclear weaponsrelated policy do not represent adjustments in strategy or 

capability but are instead diplomatic initiatives. These 

include our inauguration of a new, security-focused 

multilateral dialogue aimed at exploring potential realworld answers to future nuclear disarmament challenges -

the "Creating an Environment for Nuclear Disarmament" 

initiative - and President Trump's pathbreaking call for an 

entirely new, trilateral arms control framework involving 

both Moscow and Beijing to head off the nuclear arms race 

that might otherwise be sparked by the Russian and 

Chinese nuclear buildups currently underway. 

In February 2020, however, the United States 

announced that it had completed another piece of the 

nuclear weapons policy agenda spelled out in the 2018 

NPR: the fielding of a low-yield device on U.S. submarines: 

the Wz6-2 warhead. As the NPR made clear, this 

modification of an existing submarine-launched ballistic 

missile (SLBM) warhead had been made necessary by the 

development of new threats - specifically, by Russia's 

fielding of a broad range of non-strategic nuclear 

capabilities in search of coercive advantages at lower levels 

of conflict. (The NPR did not explicitly mention PRC 

capabilities in this context, but a similar point can be made 

about them as well.) 

Both Moscow and Beijing have worked hard in recent 

years to develop the ability to confront the United States in 

a crisis with sub-strategic nuclear threats. By design, these 

capabilities threatened to present us with an insuperable 

problem in the early stages of an escalating conflict. If they 

undertook low-yield nuclear use limited to the theater of 

conflict- something apparently embraced by Russian 

doctrine, for instance, and for which Russian forces train -

we must ensure that we do not have to choose between 

mounting a greatly disproportionate nuclear attack in 

response, or allowing Russian or PRC aggression to 

accomplish its objectives. 

An asymmetry of options would not only present 

potential escalation problems in wartime but, more 

importantly, also pointed to a potential "failure mode" for 

peacetime deterrence. To the degree that either Russia or 

the PRC calculated that the United States would not 

possess assured proportionate response options in such 

circumstances and might thus capitulate out of fear of the 

catastrophic consequences that might follow, the efficacy 

of our nuclear deterrent would be undermined, and 

aggression - and great power war-would become more 

likely. 

This was the dilemma to which the 2018 NPR proposed 

a partial solution, in the form of the supplemental low-yield 

SLBM warhead. And it was, in my view, a sound choice. 

Having gained much experience with small, forwarddeployed nuclear weapons during the Cold War, we knew 

full well how such deployments ultimately tended to be 

more destabilizing than stabilizing. We learned, after much 

study and NATO wargaming in the late 1970s and early 

1980s, that tactical weapons deployed far forward in the 

battlespace turned out to offer little deterrence value, were 

vulnerable to being overrun by the adversary's 

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Strengthening Deterrence and Reducing Nuclear Risks: The Supplemental 

Low-Yield U.S. Submarine-Launched Warhead 

Volume I, Number 4 I April 24, 2020 

conventional forces, and threatened to create terrible 

command-and-control - or loss of control - problems in 

wartime. (That's why we strongly urge other nuclear 

weapons possessors. such as Pakistan and India, not to 

continue down the dangerous path of small, forwarddeployed weapons.) So even as the Russians and the PRC 

built up their non-strategic arsenals, we were determined 

not to return to the days of forward-deployed U.S. groundbased systems such as nuclear artillery, nuclear land mines, 

or the short-range "Davy Crockett" vehicle-mounted 

missile. 

Instead, we opted to give ourselves a low-yield option 

that wasn't forward deployed, and thus demonstrably 

avoided the preemption, command-and-control, and other 

problems presented by Davy Crockett-style weaponry. 

By providing an additional, highly effective low yield 

response option in the event of Russian or Chinese theater 

nuclear use, we make such use both less tempting and less 

likely. This effectively raises the adversary's nuclear 

threshold, as well as making it less likely that deterrence 

will fail in the first place. 

The supplemental low-yield SLBM capability thus 

represents an important step in support of nuclear 

deterrence, and in reducing net nuclear risks. In sharp 

contrast with the provocative and destabilizing Russian and 

Chinese nuclear buildups currently underway, moreover, 

this is a step that the United States has taken without any 

increase in the overall number of U.S. nuclear weapons. 

Additionally, the low-yield SLBM does not circumvent the 

New START Treaty. It is, in short, a success story. 

To further illuminate many of the details of the U.S. 

reasoning behind the W76-2 in a clear public forum, I am 

pleased to offer the reader this paper prepared by the State 

Department's Bureau of Arms Control, Verification and 

Compliance. It is an excellent addition to our Arms Control 

and International Security paper series, and I hope you 

enjoy it. 

- Dr. Christopher Ford 

Assistant Secretary of State 

Performing the Duties of the Under Secretary for Arms 

Control and International Security 

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Strengthening Deterrence and Reducing Nuclear Risks: The Supplemental 

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Volume I, Number 4 I April 24, 2020 

The W76-2 Low-Yield Option 

prepared by the 

Bureau of Arms Control, Verification and Compliance 

U.S. Department of State 

In February 2020, the United States announced the 

deployment of submarine-launched ballistic missiles 

(SLBMs) armed with the low-yield W76-2 warhead. In the 

2018 Nuclear Posture Review (NPR), we identified the lowyield SLBM as a low-cost and expedient means for 

strengthening deterrence and assuring our allies in the face 

of a more threatening strategic landscape. This 

supplemental capability is fully compliant with our arms 

control obligations and does not require building and 

deploying more nuclear weapons or delivery vehicles. In an 

impressive display of strategic adaptability, the United 

States implemented this force structure modification in 

two years. 

Yet the decision to lower the yield on a small portion of 

U.S. SLBMs has generated vociferous opposition in some 

quarters. Critics continue to argue that it makes nuclear 

war more likely and is uniquely dangerous. In other words, 

they assert that the United States is not acting as a 

responsible nuclear-weapon state by deploying the lowyield SLBM. 

These are serious but incorrect allegations. Given our 

unique role in extending nuclear deterrence to over 30 

other countries, our commitment to creating the 

conditions for nuclear disarmament, and our responsibility 

to prevent nuclear war, these allegations merit a thorough 

response. 

In our judgement, the low-yield SLBM reduces the risks 

of nuclear war by reinforcing extended deterrence and 

assurance. To better illuminate why this is case, we need to 

first step back and review U.S. strategy for deterring 

limited nuclear attack, the alternative strategies, and how 

the low-yield SLBM fits into U.S. strategy. This context 

then enables an evaluation of the strategic and operational 

arguments against the low-yield SLBM. 

I. The Risk of Limited Nuclear Attack 

The highest priority of U.S. nuclear policy is to deter 

potential adversaries from nuclear attack of any scale. Any 

use of a nuclear weapon against the United States and its 

allies would fundamentally alter the nature of a conflict. 

This is not solely a U.S. view, but one that NATO shares. 

U.S. strategy for deterring nuclear attack on the United 

States and our allies encompasses much more than nuclear 

weapons and military forces; however, nuclear weapons 

play a critical role, and it is necessary to elaborate on this 

role in more detail to set the context for the low-yield 

SLBM. 

While we continue to posture our forces to deter largescale nuclear attacks, the 2018 NPR also highlighted the 

importance of deterring limited nuclear attacks on allies 

and deployed U.S. forces - something both the Oba ma and 

Trump Administrations considered more likely than a "boltout-of-the-blue" attack. This deterrence requirement is 

not new, but it has taken on greater urgency in light of the 

return of great power competition, our assessment of 

Russian and North Korean nuclear strategy, and China's 

continued military modernization, including the expansion 

of its theater- and strategic-range nuclear forces. China's 

modernization also includes exploration of low-yield 

nuclear weapons. 

For nuclear deterrence to be credible, we must also 

prepare to respond effectively, in ways that would achieve 

U.S. objectives and protect U.S. and allied interests, if 

deterrence were to fail. U.S. nuclear operations would 

adhere to the law of armed conflict. When it comes to 

limited nuclear attacks, the relationship between credible 

deterrence and effective response options is particularly 

important. If an adversary uses several nuclear weapons 

and has hundreds or thousands more ready for use, having 

a strategy to prevent further nuclear use will be an 

overwhelming objective for the United States. While some 

argue that planning for these types of scenarios makes 

them more likely to occur, the United States does not have 

the luxury of putting in place a deterrence strategy that 

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simply ignores the possibility that it may fail -that would 

be the very definition of best-case scenario planning. It 

would be irresponsible for the United States to extend 

global security commitments without accounting for the 

possibility that potential adversaries may resort to nuclear 

coercion in a military crisis. If the United States and its 

allies were unprepared to counter nuclear coercion, 

potential adversaries may conclude that a strategy of 

nuclear brinksmanship would succeed, both encouraging 

aggression and risking nuclear escalation in the ensuing 

conflict. 

Thus, as long as the threat of limited nuclear attacks 

remains, the United States must have an effective strategy 

to deter such attacks. 

U.S. strategy is best described as a counter to a limited 

nuclear war strategy: we aim to convince potential 

adversaries that any limited nuclear attack will 

fundamentally alter the nature of the conflict and fail to 

achieve its objectives. Further, such an attack will result in 

an American response that imposes unacceptable costs, 

risking catastrophic consequences. This strategy is 

intended to reduce potential adversaries' confidence in 

their ability to wage a successful limited nuclear war, 

strengthening deterrence and ensuring no adversary is 

tempted to cross the nuclear threshold. 

To illuminate how the strategy works in practice, it is 

useful to first contrast it with two competing strategies the 

United States has rejected. 

A. Massive Retaliation Strategy 

A massive retaliation strategy relies solely on the 

threat of a massive nuclear response to a nuclear attack of 

any size. Massive retaliation could take the form of either a 

massed response with many nuclear weapons or a response 

with a smaller number of weapons carrying very high-yield 

warheads. This is not a credible strategy for deterring 

Russia or China from employing a limited nuclear attack. 

Because these countries possess sophisticated, diverse and 

survivable strategic-range nuclear forces, there is a risk 

they would conclude that, if the United States only 

possessed massive response options, it would be unlikely to 

use them in response to a limited nuclear attack on allied 

territory, as doing so would invite retaliation against the 

U.S. homeland. 

For example, if Russia used one or two nuclear 

weapons in Europe, the most effective strategy for limiting 

damage against the United States and its allies would be to 

reestablish nuclear deterrence, an objective for which 

massive nuclear retaliation would be disproportionate and 

ineffective. Thus, a massive retaliation strategy does not 

provide effective response options for meeting U.S. 

objectives after deterrence of a limited nuclear attack fails. 

It is not credible, and for that reason the United States has 

not had a massive retaliation strategy since President 

Eisenhower. There is too high a risk that potential 

adversaries would choose to test it in a crisis. 

B. Mirror Image Strategy 

The second road not taken is to mirror the approach 

Russia has adopted. This strategy would essentially try to 

match Russia weapon-for-weapon at the non-strategic or 

theater-level. In other words, we would deploy up to 2,000 

ground-, air-, and sea-based non-strategic nuclear 

weapons, for the purpose of defeating Russian general 

purpose and theater nuclear forces. 

The perils and limitations of this strategy are numerous 

and obvious. Because the United States has taken steps to 

reduce the role of nuclear weapons in its national security 

strategy, we no longer possess the numbers and types of 

short-range nuclear weapons that this approach to 

deterrence calls for, and it would be massively expensive 

and take years to build an arsenal of non-strategic nuclear 

weapons of this scale. Fortunately, the United States has 

no need for a massive build-up. 

Resource requirements to the side, this strategy is still 

flawed. It undermines extended deterrence and assurance 

by suggesting that if Russia uses nuclear weapons against 

U.S. and allied deployed forces, the United States will only 

respond in kind, granting the vast Russian homeland as a 

sanctuary as long as it does not fire nuclear weapons at the 

U.S. homeland. Qualifying extended deterrence in this way 

risks lowering Russia's nuclear threshold. It also evinces a 

dangerous overconfidence in the ability to control nuclear 

escalation, as if somehow the use of nuclear weapons on 

the battlefield, so to speak, reduces the likelihood of 

catastrophic nuclear escalation, making Europe "safe for 

limited nuclear war." Even the use of the term battlefield is 

misleading, a bad euphemism for the national territory of 

U.S. allies. 

II. Deterring Limited Nuclear Attack 

In contrast to these alternatives, our strategy seeks to 

convince potential adversary leadership that it cannot 

predict the course of nuclear escalation because it will not 

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be able to predict where, when, or how the United States 

will respond. They only know that a U.S. response will be 

effective and impose unacceptable costs, the 

consequences severe but ultimately incalculable ahead of 

time. The essence of our strategy is that the United States 

will have options for responding to nuclear attack at a time 

and place of its choosing, against assets that an aggressor 

values, and in a way that reinforces the broader U.S. and 

allied strategy and objectives in the war. 

Too often, public discussion of this issue immediately 

fixates on "strategic" versus "battlefield" weapons and 

targets without sufficient attention to the overarching 

framework that guides how we evaluate nuclear force 

structure and targeting requirements. These excursions 

are typically laden with undefined jargon and miss the 

point of our strategy entirely: The leadership of any 

country that chooses to use nuclear weapons against the 

United States and its allies in a limited way should not feel 

confident that some high-value assets are off limits so long 

as they are not detonating weapons over U.S. territory. 

We do not specify exactly how we would respond in 

standing declaratory policy. Instead, the United States 

would assess all the different elements of a response 

option, including the target or targets, through the prism of 

its objectives and the circumstances at the time. Much of 

this would hinge on the specific situation at hand, but the 

2018 NPR does provide insight into our guiding principles: 

• Reestablish deterrence: If the country that used 

nuclear weapons had many more survivable weapons, 

preventing further nuclear attacks would be an 

objective. A failure to reestablish nuclear deterrence 

would likely result in more nuclear attacks on U.S. 

forces and allies (unless we capitulated). Thus, we 

would consider the adversary's intentions in 

conducting the limited nuclear strike and then 

construct a response option that conveys our resolve 

to the adversary while also signaling restraint in U.S. 

aims and military operations. Demonstrating both 

resolve and restraint would be necessary in order to 

convince the adversary that using nuclear weapons 

again is its worst option. The United States would seek 

to reestablish deterrence at the lowest level of damage 

possible. 

• Integrate nuclear and non-nuclear military operations: 

U.S. nuclear response options would need to avoid 

hindering critical U.S. non-nuclear military operations 

that are underway after an adversary nuclear attack. 

Depending on the military situation in the war, we may 

also respond in a way that reinforces U.S. non-nuclear 

military operations, not to achieve tactical goals that 

conventional weapons could accomplish, but to 

achieve a decisive impact that furthers the politicalmilitary aims of the United States and its allies. 

In this sense, our strategy for deterring limited nuclear 

war is not target-based; it is capacity-based: we deter 

limited nuclear attack by sustaining an effective military 

posture to protect the vital interests of the United States 

and its allies in the face of nuclear-backed aggression. 

A. Nuclear Forces Supporting U.S. Strategy 

In practice, all U.S. military capabilities underpin this 

strategy, but U.S. nuclear forces play a unique and critical 

role. The United States fields forces that hold a variety of 

potential adversary assets at risk with multiple types of 

delivery vehicles and warhead yields. A high degree of 

flexibility in our nuclear forces is essential, otherwise our 

underlying deterrence message would ring hollow. The 

United States does not need thousands of non-strategic 

nuclear weapons for our strategy because we are explicitly 

rejecting the notion of a war of attrition via short-range 

nuclear weapons. It does, however, need credible limited 

nuclear response options: the ability to effectively and 

reliably respond to limited use in an unpredictable variety 

of ways, including responding with a small number of 

weapons with low warhead yields. The need for limited 

response options to demonstrate resolve and restraint is a 

longstanding and bipartisan principle of U.S. nuclear policy 

and strategy. 

Transparency about U.S. nuclear forces during 

peacetime reinforces our strategy for deterring limited 

nuclear attack. The flexibility of U.S. nuclear forces signals 

to allies and potential adversaries that we have the capacity 

and willingness to counter nuclear coercion under any 

circumstances. 

B. Flawed Criticism 

Critiques of limited nuclear options and low-yield 

warheads often take aim at the weapon systems 

themselves instead of the underlying strategy they enable. 

For example, they argue that: 

• limited nuclear options are flawed because there is no 

guarantee that their use in a war would not trigger 

further escalation; 

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Strengthening Deterrence and Reducing Nuclear Risks: The Supplemental 

Low-Yield U.S. Submarine-Launched Warhead 

Volume I, Number 4 I April 24, 2020 

• possessing low-yield nuclear weapons actually 

weakens deterrence by lowering the potential costs of 

nuclear use; and 

• low-yield warheads reflect a deliberate U.S. effort to 

lower the nuclear threshold. 

In isolation, there is an intuitive appeal to each of these 

assertions, yet these arguments in a strategic context are 

unpersuasive and counterintuitive. 

It is certainly true that there is no guarantee a limited 

nuclear option with a low-yield weapon, in response to a 

nuclear attack, would prevent further nuclear attacks. We 

have to be clear eyed that nobody knows what would 

happen in a nuclear war. This uncertainty about the 

potential for further escalation is in fact a part of our 

nuclear deterrence strategy. But we can be confident that, 

while limited response options are not guaranteed to work, 

a massive response to a limited attack is even less likely to 

restore deterrence and more likely to spur further nuclear 

escalation that could devastate the world. Thus, ifwe 

accept that the United States should prepare to prevent 

additional nuclear attacks after an adversary has crossed 

the nuclear threshold, eschewing limited response options 

forecloses that possibility, turning the risk of further 

nuclear escalation into a certainty. 

But the priority of U.S. policy is to deter, not fight, a 

nuclear war. Thus, what about the argument that low-yield 

weapons weaken deterrence by signaling that the United 

States will respond in a limited, perhaps even tactical, 

fashion? 

This critique is flawed because it conflates the 

possession of low-yield weapons with a doctrine of 

responding symmetrically to limited nuclear attacks. The 

United States has no such doctrine. The full spectrum of 

adversary assets would be at risk if an adversary uses 

nuclear weapons first, and the full array of U.S. nuclear 

forces is available to strike those assets if deterrence fails. 

It is important to remember that even though a low-yield 

nuclear weapon is less destructive than a high-yield nuclear 

weapon, it is still capable of inflicting unacceptable costs. 

But because it is capable of providing an effective response 

with less collateral damage than a very high-yield weapon, 

potential adversaries may perceive it as a more credible 

response to a limited attack and thus a more credible 

deterrent to a strategy that seeks to split the United States 

from its allies. This is why we see the low-yield SLBM as 

raising potential adversaries' thresholds for nuclear firstuse. 

The preceding discussion demonstrates that the final 

critique is simply false. U.S. low-yield nuclear weapons do 

not reflect an embrace of nuclear war fighting. We are not 

seeking to make U.S. employment of nuclear weapons 

easier. We are seeking to make our potential adversaries' 

decision-making more complex and less certain when they 

consider the use of nuclear weapons against us and our 

allies. 

Ill. Rationale for the Low-Yield SLBM 

The United States needs to retain effective limited, 

low-yield responses to support its strategy for deterring 

limited nuclear attacks and coercion. Prior to the recent 

deployment of the low-yield SLBM, U.S. low-yield options 

were concentrated in bombers and dual-capable aircraft. 

These systems will continue to play an important and 

unique role. U.S. nuclear-capable bombers provide both 

penetrating and standoff response options; they are 

survivable against counterforce attacks when they are 

armed with weapons, alerted, and dispersed; and we can 

visibly signal with them in peacetime and military crises. 

Dual-capable aircraft are also valuable for signaling and 

their forward deployment in allied territory is a tangible 

demonstration of the extended deterrent link between the 

United States and its allies. 

Yet there are several distinct attributes of SLBMs that 

our air-based nuclear forces do not possess. Ballistic 

missiles are unmatched in their ability to reliably penetrate 

defenses. They are more prompt than air-delivered nuclear 

forces. And because we keep a portion of our ballistic 

missile submarines continuously deployed at sea, the lowyield SLBM provides a response option that is operationally 

survivable day-to-day and always ready. Thus, unlike our 

bombers and dual-capable aircraft, which are not armed, 

alerted, and dispersed day-to-day, we do not need to 

generate the low-yield SLBM in a crisis. 

There is a misconception that we chose to modify the 

W76 warhead to increase the overall number of low-yield 

weapons in the U.S. stockpile. In reality, we judged that 

having a small number of low-yield warheads on delivery 

vehicles with these attributes enhances our deterrence 

strategy in a number of ways, and our judgement rested on 

both near- and longer-term considerations. 

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The low-yield SLBM enabled the United States to 

quickly strengthen its forces for deterring limited nuclear 

attack. The decision to supplement existing forces with the 

low-yield SLBM reflects a qualitative judgement we made 

after an intensive, year-long assessment. We judged that 

enhancing the forces that support our strategy was the 

right and prudent step in light of the more dangerous 

security environment we and our allies now face. Russian 

strategy and its expansive modernization of its nuclear 

arsenal was a key near-term factor in our decision. This 

decision is based on more than simply a narrow analysis of 

weapons on targets. As stated earlier, U.S. deterrence 

strategy requires an effective military posture to protect 

the vital interests of the United States and its allies in the 

face of nuclear-backed aggression. We considered the 

overall capacity of the United States for deterring and 

responding to limited nuclear attacks across peacetime 

through fluid military crises and conflicts. 

The introduction of a low-yield option that is faster, 

less vulnerable to air defenses, and operationally ready 

every day guarantees the United States can respond to a 

limited nuclear attack regardless of the circumstances; as 

examples, if U.S. nuclear-capable bombers and dualcapable aircraft are committed to other missions or have 

been destroyed, or if there is an operational imperative to 

hit a target more quickly than air-based assets are capable 

of carrying out the strike. Fundamentally, this capability 

helps prevent Russia from miscalculating that the United 

States would lack the capacity to achieve its politicalmilitary objectives after a limited nuclear attack against 

NATO, or more precisely, that Russia could deny the 

United States the capacity to achieve its objectives after a 

limited nuclear attack against NATO. 

Further, the low-yield SLBM increases the resiliency of 

U.S. nuclear forces to geopolitical and technological 

challenges. Russian and Chinese air defenses will be more 

lethal in the future, as will their overall suite of capabilities 

for contesting U.S. forces in their respective regions. We 

have confidence that our next-generation air-based nuclear 

forces will be effective, but they will not be available for 

years. Every assessment of offense-defense dynamics 

between future capabilities must account for myriad 

uncertainties. The low-yield SLBM hedges the United 

States against a more demanding combat environment 

emerging in the coming decades. Even if Russian and 

Chinese anti-access and area-denial forces improve beyond 

our current assessments, the United States will have 

effective limited response options to deter limited nuclear 

use. The reason we are hedging is that penetrability is 

essential to deterring limited attacks. If the only way we 

could reliably penetrate defenses is through saturation or 

mass suppression of defenses, the profile of our response 

would be much larger; it would not appear limited to 

potential adversaries, while a more limited response might 

not be deemed credible. 

The United States is only deploying a small number of 

the W76-2 warheads. It is a testament to the wisdom of 

previous administrations that invested in and retained the 

strategic triad of delivery systems, including bombers, 

intercontinental ballistic missiles, and submarine-launched 

ballistic missiles, that the Trump Administration concluded 

only modest supplements were necessary to update the 

U.S. strategic nuclear deterrent despite a significant 

worsening of the security environment. 

IV. Debunking the Critique 

A popular argument against the low-yield SLBM is that 

the system is a uniquely dangerous weapon due to the so 

called "discrimination problem." According to this 

argument, the launch of a U.S low-yield SLBM in a war 

would precipitate a foe's decision to immediately launch a 

massive nuclear attack against the United States before 

the low-yield SLBM reaches its target. The rationale for 

this claim is that a foe's early warning system may be 

incapable of distinguishing between an SLBM carrying a 

low-yield warhead and an SLBM carrying one or several 

high-yield warheads. As a result, the foe's leadership 

would simply assume that it must launch a massive nuclear 

strike upon detection of a single SLBM launch. 

As with the arguments against low-yield nuclear 

weapons, the discrimination problem has an intuitive 

appeal; however, its underlying analysis and subsequent 

risk assessment is unpersuasive for three reasons. 

First, the discrimination problem implies that none of 

the other U.S. strategic nuclear forces possess a flexible 

range of yield options, which is incorrect. As stated in the 

2018 NPR, the gravity bombs carried by B-2A bombers and 

the air-launched cruise missiles carried by B-52H bombers 

also provide multiple yield options. Thus, while a foe's 

early warning system would not be able to determine the 

yield of the warhead on a ballistic missile that it detects, it 

would not be able to determine the yield of the weapons on 

a U.S. bomber or air-launched cruise missile either. In this 

sense, the low-yield SLBM is not unique. For example, 

Russia has long had to account for the fact that not all U.S. 

strategic delivery vehicles only carry high-yield weapons, 

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Strengthening Deterrence and Reducing Nuclear Risks: The Supplemental 

Low-Yield U.S. Submarine-Launched Warhead 

Volume I, Number 4 I April 24, 2020 

and this operational uncertainty reinforces our deterrence 

objective of undermining Russian confidence that it can 

control escalation in a nuclear war. 

Second, foreign leaders now have ample reason to 

conclude that some U.S. SLBMs carry low-yield warheads. 

The United States has been transparent since the release of 

the NPR in 2018 that it will arm a small number of SLBMs 

with the W76-2 warhead. We have actually sat across the 

table from our Russian counterparts in bilateral dialogues 

to explain what we are doing and why. Russia also has 

insight regarding both the total number of warheads 

loaded onto deployed U.S. SLBMs and the number of 

warheads on individual SLBMs through the New START 

Treaty's verification regime. If leaders in Russia or another 

nation adopt a standard operating procedure of assuming 

that every U.S. SLBM is armed with the maximum number 

of high-yield warheads it could carry, they would be 

selectively disregarding additional information about how 

the United States actually operates its SLBM force. 

Third, there is no strategic rationale for an adversary to 

use nuclear weapons in a limited way and then launch a 

massive nuclear attack upon detection of a single SLBM, 

triggering the unlimited war it is trying to avoid. 

In Russia's case, its early warning system would enable 

its leadership to assess the scale of the attack, specifically 

that it is a single ballistic missile and not a multiple missile 

launch, and the probable destination based on its 

trajectory. Therefore, Russia will have data to support the 

conclusion that the attack does not represent an existential 

threat. Moreover, the rationale for launching before the 

U.S. SLBM reached its target would be to use Russian 

nuclear weapons before the bulk of its nuclear forces or its 

nuclear command and control has been destroyed. Yet one 

SLBM, even one armed with as many high-yield warheads 

as it could carry, would not pose a comprehensive 

Arms Control and International Security Papers 

has invested in a modern force with a significant number of 

mobile delivery vehicles, the point of which is to have 

weapons that would survive a dedicated large-scale attack. 

There would be no operational need for Russia to escalate 

to a massive attack on the U.S. homeland upon detection 

of a single SLBM after it had used nuclear weapons first, 

and doing so would result in an unacceptable strategic 

outcome for Russia. 

To be clear, there is no such thing as a safe nuclear war 

or a low-risk nuclear strike, regardless of its magnitude. 

That is why we devote significant attention and effort to 

deterring the use of nuclear weapons and have adopted a 

strategy for deterring, not fighting, limited nuclear war. 

Rather, the point is that there is nothing uniquely 

dangerous about the low-yield SLBM that would preclude 

us from deploying it, given the valuable role it plays in our 

strategy for deterring the use of nuclear weapons in the 

first place. 

V. Conclusion 

Sustaining an effective deterrence strategy is central 

to our goal of ensuring that a nuclear war will not be 

fought. Nuclear deterrence is the least bad option and not 

our first choice. The United States is ready to work 

cooperatively with the international community to reduce 

nuclear dangers through effective arms control, nonproliferation, transparency, and diplomacy. As long as 

nuclear weapons exist, the United States will retain an 

effective nuclear deterrent and be transparent about the 

nuclear weapons it possesses and the reasons for changes 

to its force structure. As a nuclear-weapon state, we have a 

responsibility to do no less, and we encourage Russia and 

China to do the same. 

* * * 

The Arms Control and International Security Papers are produced by the Office of the Under Secretary of State for Arms Control 

and International Security in order to make U.S. State Department policy analysis available in an electronically-accessible 

format compatible with "social distancing" during the COVID-19 crisis.