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.
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.
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.
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.