Table of Contents

Executive Summary

In recent years, China has expended considerable efforts to build a sea-based nuclear force for the primary purpose of enhancing its overall nuclear deterrent. Although Beijing’s goal is limited and defensive, the practical implications of its efforts for regional stability and security will be significant.

Arms Race Stability

A fleet of survivable nuclear ballistic missile submarines (SSBNs) would reduce China’s concerns about the credibility of its nuclear deterrent and lessen the country’s incentives to further expand its arsenal. Such benefits, however, will be tempered by vulnerabilities associated with Beijing’s current generation of SSBNs. In the near to mid-term, developing an SSBN fleet will require China to substantially enlarge its previously small stockpile of strategic ballistic missiles, possibly exacerbating the threat perceptions of potential adversaries and causing them to take countermeasures that might eventually intensify an emerging arms competition.

China needs to use substantial general-purpose forces to protect its SSBNs in coastal waters. This requirement will become an important driver of a buildup of China’s conventional military assets. Efforts to protect Chinese SSBNs, especially in the South China Sea, could be interpreted by neighboring countries as attempts to undermine others’ freedom of navigation, to expand China’s sphere of influence, and to seek regional dominance. Such concerns could intensify already fraught arms race dynamics in East and Southeast Asia.

Crisis Stability

A sea-based nuclear capability will not make China more inclined to use nuclear weapons during a crisis. Nonetheless, the country’s emerging SSBN force will still have important implications for crisis stability. Beijing may abandon its traditional practice of maintaining a low alert level for its nuclear weapons in peacetime and instead arm its sea-launched ballistic missiles with nuclear warheads during routine SSBN patrols. There is also uncertainty over how reliable China’s SSBN command, control, and communication system is and how Beijing assesses the risk of foreign interference with this system. As a result, China may face a difficult choice between maintaining a highly centralized command and control system and giving SSBN crews some autonomy, including perhaps by pre-delegating launch authority for nuclear weapons under certain circumstances. If China concludes that it must take the latter route, the risk of an accidental and/or unauthorized launch of a sea-based nuclear ballistic missile will be higher.

Tong Zhao
Tong Zhao is a senior fellow in Carnegie’s Nuclear Policy Program.
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Moreover, China’s deployment of SSBNs will, for the first time, make its nuclear weapons vulnerable to foreign military attacks outside of the country’s territory. Foreign countries could use non-nuclear military forces, including unmanned systems, to track, trail, and attack Chinese SSBNs, creating a dilemma over how Beijing should respond if one of its SSBNs faces a conventional military threat during a crisis. As the United States and its allies continue to enhance their anti-submarine warfare (ASW) capabilities in the region, China may feel increasing pressure to reconsider its unconditional no-first-use policy. If that were to happen, Beijing may inadvertently motivate potential adversaries to further intensify their strategic ASW operations against Chinese SSBNs. Moreover, due to the technical difficulty of assessing intentions, the risk of an overreaction would increase, as China may mistake ASW operations against its attack submarines for operations against its SSBNs.

China’s likely reliance on general-purpose forces to protect its SSBNs, especially if Beijing finds it necessary to obtain sea-control capabilities and create SSBN bastions in the South China Sea, would probably heighten the risk of clashes between China’s conventional forces defending its SSBNs and enemy ASW platforms. The likelihood of incidents and inadvertent escalation may be further exacerbated by the technical and logistical difficulties of maintaining effective command, control, and communication systems in a contested maritime environment. The introduction of unmanned systems—whether surface vessels or underwater vehicles—would present further challenges, including the need for effective communication between two camps of hostile forces to avoid incidents.

Risk Reduction

Formal and verifiable arms control agreements are unlikely to be a realistic response to these risks, given the mutual distrust between the two countries and the extreme secrecy over submarine operations. Instead, cooperative and/or unilateral confidence-building measures should be pursued as the first step toward mitigating the negative potential consequences for arms race and crisis stability. At the senior political level, it is time for the United States to clarify its policy toward China’s sea-based nuclear weapons. U.S. decisionmakers should recognize that pursuing ASW capabilities against China’s SSBNs contradicts their commitment to maintaining strategic stability with Beijing. A U.S. declaratory policy that explicitly rejects the option of conducting strategic ASW against China would help mitigate Beijing’s concerns and thus discourage it from adopting a more destabilizing military posture. For its part, China should reassure the international community about the strategic objectives behind its SSBN program by shedding more light on its views about the future development of and operational requirements for its SSBN force. Doing so could help other states better assess for themselves whether China’s SSBN program is guided by the limited objective of ensuring a nuclear second-strike capability, or whether it is a more open-ended effort driven by resource availability and/or expansionist ambitions.

At the operational level, confrontations stemming from China’s efforts to protect its SSBNs and foreign ASW forces are likely to continue for the foreseeable future. It is important to start exploring possible rules of the road to regulate interactions between such forces, including in scenarios in which unmanned vehicles are employed. This process should involve both U.S.-Chinese bilateral efforts and a broader regional overture. To build trust among all relevant parties, greater transparency and voluntary restrictions by China about its SSBN operational principles and deployment postures would be helpful, as would practical steps to reaffirm China’s negative security assurances to regional countries and its early signing and ratification of the Protocol to the Southeast Asia Nuclear-Weapon-Free Zone Treaty.

Looking ahead, China should take a number of unilateral measures to further enhance strategic stability while securing its own interests. Beijing should choose to live with a relatively small SSBN force, which would be sufficient for maintaining the credibility of its sea-based nuclear deterrent. Keeping a moderate alert status for its SSBNs and not rushing to adopt continuous-at-sea SSBN patrols would also help to ensure effective deterrence without creating unnecessary risks.

Finally, there is a need for serious domestic discussions about what development and deployment strategy makes the most sense for China’s sea-based nuclear weapons. Some Chinese analysts and commentators appear to hold major misunderstandings about trends in foreign countries’ development of SSBNs and, as a result, have advocated for risky policy alternatives. More in-depth domestic debate would be useful for enhancing understanding about the costs and benefits of different SSBN development and deployment strategies. Well-informed and prudent policy choices will improve China’s own security interests, contribute to regional stability, and enhance Beijing’s international image as a responsible nuclear power.


Part of this report is based on research published as an essay called “China’s Sea-Based Nuclear Deterrent” in a larger compilation edited by Ashley J. Tellis titled “Regional Voices on the Challenges of Nuclear Deterrence Stability in Southern Asia” (Carnegie Endowment for International Peace, 2016).

This work is made possible by generous financial support from the Carnegie Corporation of New York. I would like to especially thank James Acton for his extensive advice and input throughout the project. I am very grateful to Linton Brooks and Christopher Twomey for providing constructive critiques to earlier drafts. Several Young Ambassadors at the Carnegie-Tsinghua Center for Global Policy, namely David Logan, Cole Landfried, Jason Arterburn, Raymond Wang, and Lynn Lee have provided excellent research assistance for this project. Finally, I wish to thank all the anonymous experts who have shared their insights with me, as well as the Carnegie communications team for their great help with editing and publishing the report. I am especially indebted to Ryan DeVries who has been extremely helpful as the main editor of this report. Of course, responsibility for any errors in the resulting work remains my own.