Losing Escalation Dominance: The United States, the First Island Chain and Japan’s Nuclear Outlook

CSDS POLICY BRIEF • 32/2024

By Kristin Lerfald Grostad

12.11.2024

Key issues

• The loss of the United States’ (US) escalation dominance in the East China Sea has accelerated the integration of deterrence and defence within the US-Japan alliance.
• Japan’s new defence reform seeks to strengthen resilience, boost Japan’s ability to retaliate in case of an attack and avoid being put on the sidelines of a regional conflict through a fait accompli.
• Nuclear weapons are set to play a greater part in US extended deterrence in the future. For Japan, the loss of US conventional superiority and discussions on tactical nuclear deployment represent a grave development.

Introduction

Japan’s defence reform, established through its three 2022 strategic documents – the National Security Strategy, National Defense Strategy and Defense Buildup Program –, signals a new era for the US-Japan security alliance. Much has been written about Japan’s new outlook on defence, including issues concerning Japan’s “strategic future”. Analysts have debated Tokyo’s commitment to its non-nuclear principles, discussed the likelihood of an indigenous Japanese nuclear capability and nuclear sharing with Washington, as well as how Japan can continue to uphold principles on nuclear non-proliferation and promote disarmament in an increasingly volatile security environment. Indeed, Japan’s particular position as the only country to have suffered a nuclear attack, and strong supporter of disarmament policies, create a nuclear dilemma when faced with the reality of its continued dependence on US nuclear deterrence. At the same time, Tokyo has demonstrated strong resolve in the matter of the US nuclear umbrella. For instance, Obama’s proclamations on “a world without nuclear weapons” in 2010 spurred great concern in Japan and prompted the establishment of the Extended Deterrence Dialogue (EDD).

This CSDS Policy Brief will contribute to the debate on the nuclear aspects of US extended deterrence over Japan post-2022. It considers the evolving superpower rivalry between the United States and China and the role of nuclear weapons within this dynamic. China’s nuclear and conventional expansion is challenging US extended deterrence both on the conventional and nuclear level. China’s A2/AD capabilities put US forces at risk, thus changing the strategic calculus of US military operations in the area. Likewise, Beijing’s quest for nuclear parity leads to a changed nuclear outlook for the United States. Together, China’s military modernisation efforts has resulted in a loss of US escalation dominance in the East China Sea, necessitating new deterrence concepts within the US-Japan alliance. The policy brief investigates how Japan’s defence reform fits into this picture, and how developments in US extended deterrence affects Japan’s nuclear outlook.

Loss of escalation dominance and the integration of deterrence and defence

Japan’s defence and security calculations have been intrinsically linked to US extended deterrence since the end of the Second World War. To understand Japan’s view on nuclear deterrence, it is therefore necessary to look at the development of US deterrence efforts in the region. For decades, analysts have debated a predicted decline of US power due to changes in the international environment and what some saw as an inevitable “imperial overstretch”. Others have warned of “fiscal overstretch” and overstretch of military capabilities. Despite the debate, however, US military power remained arguably unchallenged from the end of the Cold War well into the 21^st century. The role as a sole superpower has in the last few years been challenged by China, whose military power has grown to contest US dominance in the East China Sea.

Two factors have contributed to the change of power distribution between the US and China. First, Chinese A2/AD capabilities have eroded conventional US military dominance in the First Island Chain. China was recognised as a “strategic competitor” in the US National Security Strategy in 2017. Around the same time, analysts began writing about the false allure of a dominance strategy vis-à-vis China, arguing that the conventional capability balance has evened out. Since 2017, the capability gap between China and the US has shrunk even further. A Navy Admiral warned of the dangers of the eroding conventional deterrence capabilities in the Indo-Pacific in 2021. In 2023, a US Congressional reportadmitted that the Chinese military can impose costs on US operations in the East and South China Seas in a manner that affects US interests in the region. In other words, the United States no longer has the option to rely on military superiority in the East China Sea. As evidenced by new wargaming scenarios involving Taiwan, predictions of the outcome of a conflict between the two superpowers can no longer be made with certainty.

Second, although not at nuclear parity with the United States yet, China’s nuclear build-up, and persistent goal of establishing a nuclear triad, puts pressure on the US nuclear umbrella. According to the 2022 Nuclear Posture Review,China is considered an overall “pacing challenge” for the Unites States and a “growing factor” in the US nuclear deterrent. Escalation dominance against China in the nuclear sphere is therefore not viable in the long term. As explained by Aaron Miles, China has the capacity to outpace any attempts by the United States to dominate the escalation chain at the nuclear level. By 2020, Chinese nuclear modernisation had undergone considerable change, and analysts now argue for the inescapable fact of mutual vulnerability on the nuclear level between the United States and China.

Many scholars agree that we are on the verge of a third nuclear age. Although a controversial term, its definition and distinction from the second nuclear age is a useful tool to understand modern deterrence dynamics. The second nuclear age was characterised by nuclear proliferation in states more cost-tolerant than the US and its allies, and the subsequent integration of deterrence and defence. Throughout the 2000s, the United States reinforced the threat of “punishment” – embodied in nuclear weapons –, with a strategy of “denial” through conventional capabilities such as ballistic missile defence and Prompt Global Strike. These weapons were meant to decrease the risks involved in deterring smaller nuclear powers.

The dynamics of the third nuclear age follows in the footsteps of the second nuclear age by continuing the integration of deterrence and defence. Yet, it distinguishes itself in two ways. First, the third nuclear age is characterised by a return of nuclear superpower competition, this time between the United States and China. The trilateral dynamic between the three major nuclear powers, the United States, China and Russia, makes upholding non-proliferation and disarmament regimes more difficult. Second, information technology and increased computing processing power are blurring the lines between conventional and nuclear capabilities. An article by Futter and Zala on strategic non-nuclear weaponry describes the situation well. They argue that strategic non-nuclear weaponry is increasingly believed to protect against nuclear attack through missile defence and threaten an adversary’s nuclear and associated systems. Furthermore, new capabilities in the cyber realm can provide means to both defend against and attack an adversary’s nuclear forces. Lastly, Artificial Intelligence (AI) can provide improved abilities to target and monitor an adversary’s nuclear capabilities.

Japan’s defence reform and the consequences of new escalation dynamics

How do these changes impact Japan? Japan’s defence reform bears witness to the acceptance of the loss of US escalation dominance in the East China Sea, which has spurred a necessity for new deterrence concepts. In its 2022 defence reform, Japan vows to take “primary responsibility for its own defense”, invest in strike capabilities and increase resilience of its military structures and forces. Adding Japanese capabilities to the aggregate alliance capabilities will not enable the US-Japan alliance to maintain superiority over China in the East China Sea. For that, China’s military build-up has gone too far. Instead, Japan is investing in capabilities to underpin a denial strategy, hindering China’s operational capabilities. For instance, Japan is developing capabilities to retake remote islands, increase resilience in face of an attack and obtain the ability to put Chinese interest at mutual risk. The United States and Japan are moving the escalation control framework away from escalation dominance towards flexible response. As Aaron Miles puts it ‘flexible response discourages escalation by muddying the path to victory the adversary might envision’. By investing in conventional capabilities, the goal is to avoid a fait accompli in which Japan is put on the sidelines of a regional conflict involving the Unites States. This strengthens deterrence as it changes Beijing’s calculations – with high probability of Japanese involvement, US forces will have a more stable support system, for instance in terms of refueling and repairs.

What, then, for the nuclear level? The 2022 Japan National Security Strategy mentions nuclear issues 21 times, referring to security challenges in the Indo-Pacific region, reaffirming Japan’s non-nuclear principles, disarmament, nuclear power plants and strengthening extended deterrence by the United States that is ‘backed by its full range of capabilities, including nuclear’. Understandably, Japan’s three strategic documents do not openly discuss issues of nuclear deterrence. A debate on nuclear sharing emerged shortly after the release of the 2022 documents, but it was short-lived and did not lead to a broader discussion on nuclear issues in Japan. However, Tokyo has a long history of deliberating nuclear issues with counterparts in Washington, especially during changes to the security environment or to the US nuclear posture, as explained by Schoff and Samuels. For instance, they write, China’s successful entry into the nuclear club in 1964 exacerbated a fear in Japan that the presence of nuclear weapons on Japanese soil would expose the country to nuclear attacks. Debates on whether Japan was sufficiently covered by the American nuclear umbrella intensified. When looking into Japanese perceptions on nuclear weapons, therefore, it is necessary to look at how alterations to US extended deterrence affects Japan.

For Japan, the altered conventional balance between the United States and China gives nuclear weapons a greater role in deterrence in the future. Just like during the Cold War, when the United States was conventionally inferior to the USSR, the loss of conventional superiority increases the importance of the role of nuclear weapons in deterrence. Yet, there are considerable differences between the US-Soviet rivalry and the US-China rivalry.

When considering the character of the superpower rivalry between the United States and China, some scholars advocate for the importance of geographical conditions in the Asian theatre. In his book from 2018, Tunsjø argues that the “stopping body of water” will keep conflict from escalating. At the same time, because the spheres of influence in the East Asian theatre are opaque, the chance for miscalculation between the United States and China is greater than when the United States and the Soviet Union confronted one another in continental Europe. Moreover, the East and South China Seas are riddled with sovereignty disputes that were not present during the Cold War. Thus, there is an increased risk of conventional war because the role of nuclear weapons differs in maritime compared to land theatres. This makes the challenge of deterring China more difficult than deterring the Soviet Union. In such an environment, we can expect nuclear weapons to feature less prominently, while the importance of conventional capabilities in lower levels of conflict increase.

Tunsjø’s analysis of an increased likelihood of conflict between the United States and China remains valid. However, Tunsjø’s hypotheses remain underdeveloped when it comes to escalation dynamics. The emergence of a third nuclear age blurring the lines between the conventional and nuclear may impact the risk involved in a US-China war. In an article in International Security, Hiim, Fravel and Trøan point to US conventional military developments as a driver for Chinese nuclear investments. US deterrence policy in the East China Sea increasingly focuses on conventional means of deterrence. For instance, the 2018 and 2022 Nuclear Posture Reviews both stated that nuclear use, which is only considered under “extreme circumstances”, could also include a significant non-nuclear strike. Furthermore, the United States has in the past couple of years fielded long-range strike weapons to the Indo-Pacific to bolster deterrence and “address China’s military advances”.

The escalation dynamics between the United States and China are further muddled by the return of the concept of limited nuclear use. Analysts are discussing whether China is acquiring a so-called “tactical nuclear weapon” through its DF-26 missile. The DF-26 can be equipped with both nuclear and conventional warheads, which can be swiftly interchanged. Similarly, the United States fielded the low-yield W76-2 submarine-launched ballistic missile warhead to the Indo-Pacific theatre to retain flexibility in its deterrence posture against China. The US Congress has also provided continued fundingfor the Nuclear-Armed Sea-Launched Cruise Missile (SLCM-N) programme. Furthermore, the Strategic Posture Commission has advocated for the deployment of a theatre-range system of low-yield weapons to reduce China’s threshold for using nuclear weapons. Although the purpose of these developments is to ensure credible deterrence of limited nuclear use, they also end up fuelling a spiral of low-yield weapons deployment, creating a more precarious security environment for US allies such as Japan.

Nuclear deterrence considerations in East Asia are fundamentally altered, and it is not yet certain what the future holds. The need to retain the possibility of flexible response throughout the escalation ladder does not diminish the role of nuclear weapons in the US-Japan deterrence posture. Quite the contrary. For Japan, altered escalation dynamics between the United States and China further exacerbates the already grave security environment it finds itself in. Japan is set to become more dependent on the US nuclear deterrent in the future. Despite its continued push for disarmament, we should therefore expect a Japan that is increasingly persistent on nuclear issues and in its demands for reassurance from the United States.

Conclusion

Japan’s 2022 defence reform is an attempt to close the deterrence gap caused by China’s military modernisation. Through investment in conventional capabilities, Japan seeks to avoid a fait accompli that puts it on the sidelines in a regional conflict involving the US. Despite increased focus on conventional capabilities to uphold deterrence and defence vis-à-visChina, the nuclear element remains an essential part of US extended deterrence to Japan. Due to the loss of US conventional superiority and characteristics of its emerging deterrence posture in East Asia, nuclear weapons are poised to take a bigger role in intra-alliance discussions on deterrence.

The third nuclear age has introduced new challenges that necessitate a deeper integration of deterrence and defence. AI and emerging information technology threatens to put command and control systems at risk, blurring the lines between nuclear and conventional capabilities. Furthermore, China’s growing strategic forces means the US needs to deter two nuclear peer rivals, the stability amongst which is yet to be established. For the United States, extended deterrence has thus become a new ballgame in which the nuclear element features more prominently than it did during the second nuclear age. Yet, at the same time, nuclear use can be mitigated by conventional capabilities, resulting in heightened risk of limited nuclear employment.

Developments in the security environment in the East China Sea bear witness to this effect. China’s military modernisation forces the United States and its allies to adopt new deterrence strategies. The continuous development of Chinese A2/AD capabilities puts US forces operating in the area at risk and has resulted in the loss of US escalation dominance in the East China Sea. US extended deterrence can no longer rest on the laurels of nuclear or conventional superiority – at least in the East Asian region. Instead, maintaining the option of flexible response throughout the escalation ladder is a tool to shake the enemy’s confidence in its ability to prevail.

For European allies, the dynamics between the US and Japan can teach us two things. First, with regard to deterring China, conventional capabilities are becoming increasingly important due to the strategic theatre in East Asia. Deterring China is about ensuring the political elite in Beijing believes that swift military action will turn into a protracted war of which there is no clear victor. Second, US nuclear modernisation is likely to continue and follow the developments in China. So long as China refuses to adhere to any disarmament regime, the United States has limited incentive to enter into bilateral agreements with Russia. In other words, the US-China nuclear dynamic also has consequences for Russia’s nuclear posture.

__________