Over the Brink

Executive Summary

A new era of nuclear deterrence is taking shape in the Indo-Pacific theater. As the People’s Republic of China (PRC) dramatically expands and modernizes its nuclear arsenal, the risks of PRC nuclear coercion and escalation are evolving. Building on the authors’ prior work on U.S.-PRC nuclear escalation risks and protracted U.S.-PRC conflict, this report examines the United States’ ability to manage nuclear coercion in a hypothetical protracted conflict over Taiwan. To this end, the authors conducted two tabletop exercises (TTXs) and supplementary research to better understand the challenges of U.S.-PRC intrawar deterrence.

Findings Summary

This study finds that a hypothetical, protracted U.S.-PRC conflict creates conditions under which nonstrategic nuclear weapons use is both appealing to the PRC and difficult to manage for the United States. Moreover, once nuclear escalation in the Indo-Pacific occurs, reciprocal tactical nuclear exchanges may continue, but not necessarily lead to general nuclear war. These findings reflect the fundamental differences of deterrence in the emerging Indo-Pacific era, where distinct geography, targets, and capabilities make limited nuclear escalation potentially more tolerable than in the Cold War era.

The authors further found that the United States is currently ill-equipped in doctrine, capabilities, and concepts to manage this nuclear future. Relying on submarines and dual-capable fighters and bombers for signaling and employment, the United States may encounter issues related to platform vulnerability, signaling visibility, and conventional warfighting. Additionally, the TTXs highlighted major divergences of opinion on nuclear retaliation that will likely challenge U.S. decision-makers and that may result in capitulation, compromises, or ineffective counter-coercion approaches.

This report also illuminates a critical area for future study: the role of allies and partners within a broader U.S. escalation management strategy. The United States needs to maintain alliance cohesion and the credibility of extended deterrence represents a logical target for PRC nuclear coercion, particularly when facing a disadvantageous conventional balance. Across the TTXs, nuclear strikes on U.S. allies were viewed as key strategic turning points. For these reasons, strengthening extended deterrence and improving escalation management coordination are crucial areas for future study.

Methodology

The authors developed and executed two TTXs, conducted supplemental research, and crafted a novel escalation model linking conventional warfighting to nuclear deterrence.

The study’s TTXs each posited a hypothetical nuclear employment logic in which China sought to achieve favorable conflict termination through limited nuclear escalation. The first case, Spike the Ball, posited PRC limited nuclear use when China was marginally advantaged. The second, Cold Stop, posited limited PRC nuclear use when China was marginally disadvantaged. Following a scripted Red nuclear strike against multiple U.S. military targets at the conclusion of the first move, both games moved into traditional free play for two to three turns to test U.S. ability to manage and respond to Chinese nuclear escalation.

Building on analysis of the TTXs and supplemental research, the authors subsequently developed a novel escalation model. This “conventional-nuclear crossfade” framework underscores how nuclear escalation risks are nonlinear and how, in a protracted Sino-American conflict in the Indo-Pacific, an inversion of conventional and nuclear escalation risks may render limited nuclear exchanges both more credible and more tolerable. The escalation risks associated with conventional and nuclear actions are likely to blur, lending nonstrategic nuclear weapons an uncomfortable yet plausible logic for employment.

Key Findings and Recommendations

FINDING

Protracted conventional conflict with the PRC heightens the potential for nonstrategic nuclear weapons use due to decreasing conventional capabilities, increasing nuclear signaling and use options, and the nature of the theater. Protraction’s reduction of preferred conventional munitions increases the perceived utility of higher-efficiency nuclear weapons. Additionally, the Indo-Pacific’s archipelagic and maritime nature lends itself to small numbers of air-bursted weapons compared to the Cold War confrontation in central Europe. These differences increase the perceived tolerability of nuclear use.

RECOMMENDATIONS

• Educate senior U.S. decision-makers on the troubling logic of theater nuclear use and corresponding limits on U.S. responses. Senior decision-makers must look beyond the PRC’s longstanding declaratory policy and understand both the dangerous potential branches of Chinese nuclear futures and corresponding limitations on U.S. responses.
• Pursue dialogue and confidence-building measures where possible with the PRC, even when there is a perception of limited movement. The United States and its allies should continue to engage with PRC interlocuters wherever possible to create pathways for dialogue and understanding. In doing so, U.S. diplomats may be able to achieve real progress on sensitive, nuclear-adjacent issues.

FINDING

U.S. regional allies are a clear strength and potential vulnerability. U.S. allies and partners are key in deterring China and maintaining a “free and open Indo-Pacific.” China may use nuclear arms to undermine or break U.S. extended deterrence commitments and thus the underlying alliances.

RECOMMENDATION

• Hold detailed planning conversations with Japan and Australia on responses to nuclear use. U.S. diplomats and senior military officials must begin forthright discussions on the implications of PRC nuclear expansion for U.S. allies and partners. This level of coordination must include plans for resilience, redundancy, and forces operating in contaminated environments.

FINDING

The United States lacks the doctrine, capabilities, and concepts to manage the conventional-nuclear crossfade. U.S. nuclear thinking and systems remain tied to the Cold War, and current capabilities suffer from a lack clear of signaling tools and employment difficulties.

RECOMMENDATIONS

• Fully integrate nuclear activities into U.S. planning and exercises, not just as a “last day” or stand-alone exercise. Reviving this skill for great power competition and potential U.S.-PRC conflict generates a powerful signal that U.S. forces are alert to the threat of nuclear escalation and lessens the operational advantages that an adversary may seek to gain through limited nuclear use.
• Develop and exercise operational concepts for visible theater nuclear generation. Given the inherent signaling limitations of ballistic missile submarines, the U.S. Air Force must develop the tactics, techniques, and procedures to move nonstrategic nuclear weapons quickly and safely to theater and mate with forward-deployed aircraft.
• Improve both the capabilities and capacities of conventional munitions. To avoid a dangerous dependence on theater nuclear arms, the United States must fund expanded conventional munitions capabilities to include area-effects weapons, “good enough” weapons that can be produced en masse, and a substantially higher capacity of preferred conventional munitions.
• Consider expanded theater nuclear weapons capabilities. The United States likely lacks the theater nuclear capabilities necessary to engage in effective conflict management and forestall successful nuclear coercion. For this reason, the United States should consider the development of a small number of nuclear-tipped antiship capabilities to increase the flexibility of U.S. theater nuclear capabilities and better align legacy Cold War capabilities with the Indo-Pacific age.

Introduction

During the Cold War, Western scholars labored to develop theories and approaches for managing escalation and gaining advantage in the competition between the United States and the Soviet Union.¹ While most of these theorists focused on preventing conflict, a smaller subset of scholars considered more pernicious questions: how might a conventional war escalate to the nuclear level—and would nuclear war be controllable?² Thankfully, these theories were never put into action and this line of inquiry was truncated by the fall of the Berlin Wall and the end of the Cold War era.

Strategists in the United States are currently asking many of these same questions about competition and potential conventional conflict with the People’s Republic of China (PRC).³ While a variety of experts have studied the PRC’s conventional modernization for over a decade, consideration of the nuclear dimensions of the PRC’s evolving military capabilities has, until recently, been largely relegated to a small community of specialists. This relegation can be attributed in part to China’s minimalist nuclear strategy, which emphasizes assured deterrence and no first use, and to its relative lack of nuclear warfighting capabilities.⁴

Over the past five years, it has become clear that the PRC is dramatically expanding both the quantity and quality of its strategic nuclear forces. This includes new mobile missile systems (DF-31AG and DF-41), enhancements to submarine-launched ballistic missiles (JL-3), modernization of the air leg (H-6N), and most dramatically, construction of over 300 hardened intercontinental ballistic missile (ICBM) silos.⁵ The 2023 China Military Power Report suggests that the PRC will have 1,000 operational warheads by 2030.⁶ As recently as 2020, the U.S. Department of Defense (DoD) estimated that the PRC’s operational stockpile was “in the low 200s,” and claimed that it grew to 500 warheads in 2023.⁷

PRC leadership has clearly decided on markedly increasing their nuclear capabilities but has failed to explain the overarching strategic rationale for this expansion. Many U.S. analysts view this lack of strategic clarity with alarm.⁸ At a minimum, it increases the chances of misunderstanding and misperception. While the exact rationale behind the PRC’s qualitative and quantitative nuclear expansion is unclear, these efforts will enable China to potentially change its current nuclear strategy of assured deterrence. There are signs that the People’s Liberation Army (PLA) is moving toward a launch-on-warning posture, and increased capability and capacity creates previously unavailable strategic options for PRC leadership.⁹ Regardless of the state of PRC nuclear strategy today, presently observed changes in its arsenal create the possibility of future changes in its strategy. The Indo-Pacific era thus requires a revaluation of the strategic tools built during the Cold War.

It is this uncertainty that compels U.S. strategic analysts to ask uncomfortable “what if” questions about PRC nuclear strategy. These questions are most concerning when considering how relative strategic parity influences the stability-instability paradox and opens the window for discrete, nonstrategic nuclear strikes.¹⁰ The PRC’s nonstrategic nuclear capabilities are particularly opaque. Much has been written about the dual-capable nature of the DF-26 IRBM and the potential to quickly “hot swap” the payload between conventional and nuclear warheads.¹¹ There is very little to no publicly available information on the quantity of PRC tactical warheads. It is apparent that the PRC has dramatically expanded the quantity of DF-26 launchers over the past five years.¹² While details on PLA thinking remain sparse, small-yield, precise nonstrategic nuclear arms neatly fit into the PLA’s conventional warfighting approaches and are being discussed in Chinese military writings.¹³