Amid rapid geopolitical change at the start of the 2020s, unfolding now in the Covid-19 crisis, nuclear weapons manifest grim continuity with the previous century. Especially persistent is a capability that has existed since the 1960s: the deployment of nuclear weapons on submarines. The ungainly acronym SSBN represents nuclear-powered ballistic missile submarines: the most destructive armaments carried on a supposedly undetectable, and thus invulnerable, platform. Over several articles, this series will illuminate new technologies and potential risks relating to undersea warfare and nuclear deterrence in the Indo-Pacific over a 20-year timeframe.

The various undersea nuclear deterrence programs ^[1] in the Indo-Pacific region can’t be considered in isolation or solely in relation to one another. There’s a large and complex strategic context to the decisions by China, India, Pakistan and North Korea to invest in submarine-launched nuclear weapons programs, by the United States and Russia to modernise their own, and by the United States and its allies—notably Japan and Australia—to double down on their advantages in anti-submarine warfare.

Nuclear strategy can’t be divorced from multi-layered maritime competition involving everything from territorial disputes to resource exploitation to conventional naval operations. The contest for authority and control in the South China Sea ^[2] isn’t simply about fish, energy resources, nationalism and history, but has a bearing on the balance of military power and prospects for coercion or deterrence in a crisis, right up to the nuclear level. Meanwhile, Chinese and American investments in disruptive technologies ^[3]—such as quantum computing, artificial intelligence, autonomous systems and new sensing techniques—are part of a broader strategic competition related in part to deterrence in the maritime domain.

Serious complications arise, however, given the increased assertiveness ^[4] of China’s wider strategic activity. Even if the Pentagon’s warnings of China’s hegemonistic ambitions are less than fully substantiated, it is clear that China under President Xi Jinping has set for itself strategic objectives that run counter to interests that other nations, and of course Taiwan, are willing to defend. Several of the region’s long-standing ‘flashpoints’ involve these clashes of interests, including territorial disputes in the South China Sea and in the East China Sea. The most obvious flashpoint involves Beijing’s insistence, enshrined in the so-called Anti-Secession Law, that it will use force to prevent Taiwan from formalising its independence.

Most of the many tensions that accompany China’s strategic assertiveness are in themselves unlikely to lead to armed conflict, let alone escalation to nuclear threats. In the South China Sea, Beijing has often been careful to rely on paramilitary coastguard units and militias to bully Vietnam and the Philippines, rather than resorting to direct application of naval force, but that may be changing. That said, Vietnam in particular has the emerging military capability to put Chinese forces at risk, at least in the early stages of a clash. More profoundly with regard to the nuclear issue, one credible explanation for China’s campaign of building and militarising islands in recent years has been its wish to secure control of the South China Sea to make that area an SSBN bastion. Disturbingly, the global shock of Covid-19 has barely interrupted China’s efforts to dominate the South China Sea.

In the East China Sea, China has for the moment backed away from high-risk confrontations with capable (and now reinforced) Japanese forces, not least following clarification that the US considers its security treaty to apply to clashes over the islands in question. In the Indian Ocean, it’s difficult to imagine a China–India confrontation—for instance, over the fate of a small island state such as the Maldives—escalating to war, although reports have surfaced that even the land-border clash at Doklam led Delhi to look for ways to remind Beijing of the nuclear factor. In North Asia, crisis scenarios involving the Korean peninsula could lead to US–China confrontation, but they could also lead to a degree of US–China cooperation, with the principal nuclear threat being the regime in Pyongyang, not each other.

In the end, however, the clearest prospect of armed confrontation between China and the US leading to nuclear threats continues to revolve around the status of Taiwan. There is a strategic logic to the PRC gaining military control over Taiwan, to break through China’s geographic constraint by way of the ‘island chains’ and secure access to the open Pacific. It would be an oversimplification to argue that a Taiwan crisis would escalate quickly to the nuclear level. There would be several ways for Chinese forces to initiate coercion, include economic blockade and cyberattacks. And the subsequent conflict could drag out on multiple levels, including international economic and diplomatic pressure on China.

Nonetheless, a Taiwan crisis—or indeed another conflict, such as one arising from a US–China skirmish in the South China Sea—could lead to a wider mobilisation of forces, including Chinese SSBNs and US and allied anti-submarine warfare assets, perhaps with nations pre-empting each other rather than necessarily planning to attack.

The role of China’s immature SSBN fleet in such a situation is unclear, but a few credible possibilities exist. It seems highly unlikely that China would threaten nuclear attack on Taiwan: it claims, after all, to be liberating its misguided compatriots. Nonetheless, wanting to reserve the right to retaliate to a future US nuclear attack, and thus seeking to discourage US conventional military intervention as well, Beijing could well choose to take precautions to protect its nuclear forces at an early stage. In the case of the SSBN fleet, this could involve putting boats to sea as soon as possible rather than keeping them inside their hardened ‘dens’ on Hainan.

Will future ‘game-changing’ detection technologies ^[5] render the oceans transparent? Such a breakthrough threatens the assumption that SSBNs are invulnerable—core to the concept of strategic stability. Amid this uncertainty, it’s clear that undersea nuclear deterrence in the Indo-Pacific is increasingly complex, as both established and emerging players deploy more of their nuclear arsenals underwater. We know that strategy, geography ^[6] and technology in relation to undersea nuclear deterrence had profound implications for stability during the Cold War, and can safely surmise that they will again in the future of the Indo-Pacific.

This piece was produced as part of the Indo-Pacific Strategy: Undersea Deterrence Project ^[7], undertaken by the ANU National Security College ^[8]. This article is a shortened version of chapter 1, ‘Undersea deterrence and strategic competition in the Indo-Pacific ^[9]’, as published in the 2020 edited volume The future of the undersea deterrent: a global survey ^[10]. Support for this project was provided by a grant from Carnegie Corporation of New York.