In June, Republican lawmakers adopted an amendment to the 2024 National Defense Authorization Act to develop a sea-launched nuclear cruise missile and recently included funding in appropriations legislation for the Department of Energy. This would override the Joseph R. Biden administration’s decision to cancel the program, announced in the 2022 Nuclear Posture Review, and it rekindled a debate on its merits.
The new missile would effectively reconstitute a retired Cold War system, the nuclear-armed version of the Tomahawk land attack cruise missile, which could strike targets at ranges of 2,500 kilometers (or roughly 1,550 miles).
While critics have rightly focused on the program costs and timing of delivery, potential operational challenges for the Navy, and redundancy, proponents have countered that the new cruise missile will enhance deterrence and reassure allies facing adversaries with stocks of tactical nuclear weapons. This is an important claim and ultimately central to whether the program is worthy of funding. However, the deterrence and reassurance benefits of a sea-launched nuclear cruise missile are vastly overstated and may actually undermine the ability of the United States to deter adversaries by diverting scarce resources away from investments in more useful conventional platforms and munitions.
The Donald Trump administration’s 2018 Nuclear Posture Review articulated the rationale for the new missile as necessary to “expand the range of credible U.S. options for responding to nuclear or non-nuclear strategic attack; and, enhance deterrence by signaling to potential adversaries that their concepts of coercive, limited nuclear escalation offer no exploitable advantage.” Without such a capability, adversaries possessing tactical — or theater-range — nuclear weapons could be tempted to execute limited strikes against U.S. and allied forces in a future conflict. The deployment of a nuclear cruise missile on naval assets deployed in the region would remove any incentive to consider such limited use because U.S. forces could promptly and proportionately retaliate.
The size and scope of the program remain unclear. The Congressional Budget Office recently assessed the cost savings of cancellation as approximately $10 billion for the development of the missile and low-yield warhead over the next seven years. This represents a substantive program, implying deployment on attack submarines as well as surface vessels. In 2018, then–Strategic Command commander Gen. John Hyten noted that the sea-launched nuclear cruise missile would not be limited to submarines and might also be deployed on Zumwalt class destroyers. With the program’s cancellation, advocates have pressed for limited deployment on attack submarines utilizing an existing warhead — the W84-4 — that is planned for use with an air-launched cruise missile as part of the long-range standoff program.
While such a limited program would be highly vulnerable to claims of redundancy given the deployment of the low-yield W76-2 warhead for the Trident submarine-launched ballistic missile, the confusion around the program underscores the perceived need for a capability without a clear explanation of its potential contributions to regional deterrence and reassurance missions.
Capability Absent Commitment: A Flawed Approach to Deterrence
Estimating the deterrent effect of a specific action on an adversary’s decision-making is inherently speculatory. But the assumption that perceived gaps in capabilities incentivize adversary behavior, and therefore necessitate an offsetting or in-kind response to maintain or enhance deterrence, is dubious. It is far more useful to assess specific policies against alternatives starting with the critical questions “who is being deterred” and “from doing what” in the context of concrete scenarios. Capabilities are important for deterrence, but the perceived will to use those capabilities, based upon the underlying political commitment a country is upholding, is just as important to credibly signal with nuclear weapons.
While Russia’s war in Ukraine and reckless nuclear threats may provide some rationale to enhance existing deployed U.S. tactical nuclear capabilities in Europe, the more relevant target of sea-launched nuclear cruise missiles seems to be China. With the rapid expansion of Chinese conventional military capabilities, coupled with General Secretary Xi Jinping’s more aggressive rhetoric concerning the reunification of Taiwan with the People’s Republic of China, the probability of a crisis or military conflict has increased. Moreover, China’s growing strategic nuclear arsenal and extensive stock of short- and intermediate-range missiles, some of which could carry nuclear warheads, are a threat to U.S. and allied forces and may create a “gap” in the ability of the United States to deter China from taking unwanted military action.
The projected gap would emerge with the Chinese military’s expected deployment of tactical and theater nuclear weapons by Beijing in the next decade, while the United States will not possess an analogous missile capability in the region. This could allow the Chinese government to raise the stakes in a future crisis or conventional conflict by engaging in limited nuclear use, ostensibly forcing a U.S. president to make a stark choice between military escalation or accepting defeat. While the deployment of a sea-launched nuclear cruise missile may ostensibly provide additional options in the event of a conflict — that is, if deterrence fails — the underlying deterrent logic for its deployment is dubious.
Advocates of the sea-launched cruise missile program imply that it will enhance general deterrence. As a result, the probability that an adversary would undertake provocative action in the first place would decrease, making the United States and its allies more secure. But more than the mere presence of the capability, the perceived willingness to use it is of critical importance to deterrent effect. Despite the sea-launched cruise missile’s low-yield warhead (and perceived “usability” in a conflict), it is difficult to envision a scenario in which the United States would resort to the first use of nuclear weapons.
Since the end of the Cold War, the policy of successive U.S. presidential administrations — including the Trump administration — has been to limit the United States’ reliance on nuclear weapons. Today, “the United States would only consider the use of nuclear weapons in extreme circumstances to defend the vital interests of the United States or its Allies and partners.” While the U.S. government maintains close relations with the Taiwanese government, the United States has no formal treaty obligation to defend the country, fostering the “strategic ambiguity” that has defined U.S. policy since the 1979 Taiwan Relations Act. Polling indicates that while a plurality of Americans would support Taiwan in the event of an attack by China, direct military action to defend the island remains unpopular. These are neither the diplomatic nor the domestic political foundations for a credible threat of limited nuclear use in response to conventional aggression by China.
If the Chinese government deliberately targeted U.S. allies early in the conflict, beyond U.S. bases, the U.S. military has the capability and flexibility to retaliate with nuclear weapons if deemed necessary and appropriate. However, the prospect of first use of nuclear weapons by the United States in a conventional conflict involving Taiwan is highly improbable given the fundamental underlying asymmetry of interests. Even in the context of heavy U.S. and allied losses from a highly coordinated, conventional “bolt from the blue” attack on bases in the region (perhaps even targeting Andersen Air Force Base on Guam), U.S. leaders would be pressed to respond with conventional forces.
Deterring What? A Missile in Search of a Mission
This raises the question of whether the presence of sea-launched nuclear cruise missiles in the region would deter China’s limited use of nuclear weapons in a future conflict. Beyond Beijing expressed commitment to a “no first use” doctrine, under almost any imaginable scenario China would have little incentive to use nuclear weapons early in a conflict precisely because of its existing local and growing regional conventional military superiority. If Xi Jinping decided to move against Taiwan, he would likely do so with confidence that Chinese conventional forces could defeat or seriously degrade U.S. forces in the immediate vicinity and achieve initial campaign objectives. In this way, U.S. theater nuclear forces would be “deterring” something that was unlikely to happen.
In considering a scenario of limited nuclear use during a protracted conventional conflict in which both sides have taken significant losses, the question of targets and the potential for escalation become a central concern. Under the stresses of early defeats and the tide of conflict turning against it, or if its strategic nuclear forces came under attack, the Chinese leadership may contemplate using tactical or theater nuclear weapons to avoid a potentially catastrophic outcome. But under these conditions, it is difficult to see how the presence of U.S. tactical nuclear weapons in the region would necessarily prove decisive in shaping China’s calculations. Rather than a “prompt” response that does not require “force generation” from outside the region, the United States may prefer to maintain the tempo of conventional campaign operations and forego immediate escalation, though it would possess assets — the low-yield sea-launched ballistic missile and the long-range standoff cruise missile deployed on bombers — that are suitable for controlled response at a time of the president’s choosing.
Warfighting, without Deterrence
Nuclear cruise missiles could theoretically be used against a Chinese fleet in the Taiwan Straits — something Chinese planners have reportedly considered, according to the Pentagon’s 2023 Report on Chinese Military Power. However, this would seem to be an unrealistic option because it would only have a significant impact early in the conflict and would most likely entail first use by the United States at a much lower level of conflict.
In response to Chinese first use and the prospect of a “limited” nuclear exchange, high-value military targets for sea-launched nuclear cruise missiles would primarily be on the Chinese mainland, confronting the United States with crossing an obvious “red line” and inviting Chinese escalation to further theater and possibly even strategic retaliatory strikes, especially as China’s nuclear forces expand and improve. Precisely because of the perceived asymmetry of interests, and a likely asymmetry of capabilities — despite the deployment of sea-launched nuclear cruise missiles — Beijing will have an incentive to escalate further, placing Washington in an extremely difficult position. Because of the likelihood of sparking unwanted — and possibly uncontrolled — retaliation, the perceived benefits of the sea-launched nuclear cruise missile — proportionality, flexibility, and control —dissolve in such a scenario.
Missing the Mark: Failing to Address the Conventional Balance
Finally, the deployment of nuclear cruise missiles aboard U.S. Navy vessels will do little to address the fundamental source of any perceived decline in the credibility of the U.S. deterrent: the deterioration of the conventional military and naval balance in the western Pacific. Broadly speaking, deployment of nuclear weapons cannot rectify a perceived imbalance in conventional forces in the region. Moreover, as others have noted, the deployment of sea-launched nuclear cruise missiles on surface vessels may create discrimination problems, which are concerns that an adversary cannot discern whether a missile is armed with a conventional or a nuclear warhead. In this scenario, Chinese leaders may overreact during a crisis involving conventionally armed cruise missiles, leading to inadvertent escalation, which may further complicate the U.S. Navy’s ability to execute operations.
Deployment of sea-launched nuclear cruise missiles on nuclear-powered (but conventionally armed) attack submarines may undermine their effectiveness in the event of a crisis or conflict in two important ways. First, the mission to execute a nuclear cruise missile strike will necessarily involve the submarine making its location known to the adversary, and thus vulnerable to counterattack. Second, and perhaps more important, that mission — almost by definition — would distract the attack submarines in the region from their central mission, locating and sinking enemy attack or ballistic missile submarines and surface vessels. This is a highly problematic aspect of the deployment of sea-launched nuclear cruise missiles across the attack submarine fleet, which some naval experts already view as insufficient to address growing threats as currently constituted.
Advocates may believe that the conventional balance has shifted so far in China’s favor that the United States requires a dramatic shift in policy to consider greater reliance upon nuclear weapons to deter and defeat a conventional attack. If so, they should make the case explicitly, because it would represent a departure from U.S. national security thinking and have potentially dramatic political-military and diplomatic implications for U.S. policy in the East Asian region and around the globe. Even with such a shift in policy, sea-launched nuclear cruise missiles are a poor substitute for a decline in conventional military power, and resources are more wisely spent elsewhere.
Reassurance: Even Less than Meets the Eye
In terms of reassurance, the case for sea-launched nuclear cruise missiles is even less compelling. Simply increasing the number of nuclear weapons in the region is not likely to have a meaningful impact on allies’ perceptions of U.S. commitment to their security. In fact, it could have the opposite effect. A dramatic shift to a new reliance on tactical and theater nuclear weapons may signal panic and a lack of confidence in existing and planned conventional capabilities. Deployment of enhanced conventional forces, coupled with extensive diplomatic outreach and intensive, high-level consultations, is likely to be far more effective in responding to allied concerns. More importantly, no weapons program — whether nuclear or conventional — can overcome messaging from Washington that disparages allies or questions the benefits or relevance of existing alliance commitments.
It is also worth recalling that during the Cold War, the presence of dedicated U.S. ballistic missile submarines and surface vessels (some carrying nuclear-armed Tomahawk cruise missiles) were explicitly determined to not constitute a sufficient response to the Soviet deployment of the vaunted SS-20 intermediate-range ballistic missile system in the 1970s. That crisis in NATO confidence precipitated the deployment of the Pershing II intermediate-range ballistic missile and the ground-launched cruise missile on the territory of several European allies. It also precipitated a public backlash across Western Europe; it underscores the high threshold to effectively signal commitment in the face of an acute threat. The deployment of nuclear cruise missiles, while having the benefits of avoiding domestic political challenges of deployment of strike assets on the home territories of nervous allies, is likely to have only marginal reassurance benefits, at best.
Conclusion: Cancellation Was the Right Move
Ultimately, the sea-launched nuclear cruise missile is an unnecessary distraction from addressing the major challenge confronting the United States in deterring unwanted actions by China, reassuring East Asian allies, and supporting long-term strategic competition: the deterioration of U.S. conventional military capabilities. This problem is not new. It has taken decades of neglect, mismanagement, and ineffectual Congressional oversight. At the same time, while conventional needs should demand priority, Washington must also be cognizant of the threats and opportunities arising from emerging technologies, which will shape the ability of the United States to achieve its national security objectives over the long term. The current nuclear modernization program of record provides ample strategic deterrent capabilities and can be adjusted to address specific threats arising from the actions of China, Russia, and regional nuclear powers. But the sea-launched nuclear cruise missile is a costly, redundant program with minimal deterrent or reassurance benefits and thus should remain cancelled.
David W. Kearn, Jr., is a visiting scholar at the Project on Managing the Atom and the International Security Program at the Harvard Kennedy School. He is also an associate professor of government and politics at St. John’s University.
Image: U.S. Navy photo by Mass Communication Specialist 2nd Class William Collins III
