The Credibility Challenge: US Extended Deterrence in the Indo-Pacific

The US faces a credibility challenge in the Indo-Pacific. Allies like Japan and South Korea see Russian nuclear threats in the unfolding Ukraine war and question the US's willingness to defend them wholeheartedly in a conflict with China or North Korea. Simultaneously, adversarial tensions and capabilities are on the rise. The US Department of Defense estimates that China could more than triple the size of its nuclear arsenal by 2035. North Korea continues to develop and field more sophisticated nuclear weapons technologies, including by conducting missile tests that fly over Japan. The US commitment to extended deterrence, the promise to defend allies with its own nuclear capabilities, forms the bedrock of its security alliances in South Korea, Japan and Australia. To adjust to a world where China is drastically increasing the size and scope of its nuclear weapons capabilities, the US has and must continue to pursue its strategy for extended deterrence in the region, bolstering conventional capabilities and communication to reassure allies and maintain stability.

Japan: Seeking a Stronger Shield

Japan, a key US ally, also faces growing anxieties about regional security. North Korea's missile tests regularly overfly Japanese territory, and China's military activities around the Senkaku Islands have raised tensions. Japanese Prime Minister Ishiba openly shared his personal thoughts on the Japanese security environment before taking office in a September Hudson Institute commentary. PM Ishiba noted the absence of a collective self-defence mechanism in Asia and proposed the creation of an Asian version of NATO, including the stationing of US nuclear weapons in the region.

Despite these challenges, a security arrangement in Asia like NATO is both unlikely and unnecessary at the current time. Japan’s current Foreign and Defence ministers have already rejected the pursuit of an “Asian NATO.” A collective self-defence arrangement would require more robust security collaboration between Asian states. In the US, passing any treaty would require considerable bipartisan support and congressional approval, which is rare. The last security agreement that the US Senate ratified was the New START Treaty in 2011. Additionally, the US would require significant changes to deployed forces and capabilities in the Asia Pacific.

It is more likely that the US would work with Japan to forge something similar to the Nuclear Consultative Group with South Korea. The NCG, established in April 2023 by the Washington Declaration, enables joint military planning between the ROK and the US to respond to North Korean nuclear use. Creating a more informal consultative body with Japan could complement ongoing US-Japan Extended Deterrence Dialogues and enable a larger role for Japanese military officials in joint planning exercises. A robust nuclear planning group between the US and Japan could help alleviate the US’s extended deterrence credibility challenge by enhancing dialog and preparations while avoiding the challenges associated with creating a full regional security alliance.

This reflects a desire for greater collective security and a more proactive role for Japan in regional defence. However, such proposals face significant challenges, including historical sensitivities and potential resistance from other Asian nations. Moreover, it raises questions about the extent to which Japan is willing to rely on the US security guarantee, particularly if Washington is perceived as hesitant to fully commit to Japanese defence.

South Korea: Doubts and Demands

South Korea, living under the constant threat of North Korea's nuclear and missile programmes, has long relied on the US nuclear umbrella. However, recent developments have shaken public confidence in this guarantee. President Yoon Suk Yeol has openly expressed concerns about the reliability of US extended deterrence, even suggesting the possibility of South Korea acquiring its own nuclear weapons if the threat escalates. In a statement in January of 2023, he said, “It’s possible that the [North Korean] problem gets worse, and our country will introduce tactical nuclear weapons or build them on our own.” This reflected a growing sense of vulnerability and a desire for more concrete assurances from Washington.

The Washington Declaration attempted to address these concerns by establishing a Nuclear Consultative Group (NCG) and promising greater information sharing and joint decision-making on nuclear deterrence. While a positive step, it remains to be seen whether this "software upgrade" will sufficiently reassure Seoul or will be continued by future US administrations. Some argue that it falls short of South Korea's desire for a more explicit and binding commitment, potentially leaving room for doubts to linger.

Some senior Republicans have claimed that the US should go further and consider deploying nuclear weapons in the Indo-Pacific. For example, Senator Roger Wicker, the highest-ranking Republican member of the US Senate Armed Services Committee, produced a report exploring the deployment of US tactical nuclear weapons in South Korea. Chinese government officials condemned the report, claiming that the US redeployment of nuclear weapons to the region would undermine regional peace and security.

Australia: Navigating the AUKUS Dilemma

Australia, geographically distant but strategically aligned with the US, has also sought to bolster its security amid growing regional tensions. The AUKUS agreement, announced in 2021, aims to provide Australia with nuclear-powered submarines, enhancing its naval capabilities and strengthening its alliance with the US and the UK. Pillar two of the AUKUS agreement enhances joint capabilities in several fields, including hypersonics and counter-hypersonics, cyber, artificial intelligence, quantum technologies and additional undersea capabilities.

This agreement has faced criticism for potentially fuelling a regional arms race and undermining the non-proliferation regime. The US has made clear that the AUKUS arrangement will be conducted with the highest non-proliferation standards and is working closely with the IAEA. Additionally, the US has placed high levels of built-in safeguards on the reactor itself. For example, the plutonium that fuels the reactor will not need to be removed for refuelling for the entire life of the submarine. Additionally, chemical separation of the plutonium would be incredibly challenging.

Perhaps more importantly, AUKUS raises questions about the unequal level of US commitment to extended deterrence in the region. The United States has a long history of deep ties with Australia, including through The Five Eyes (FVEY), an intelligence alliance between Australia, Canada, New Zealand, the United Kingdom, and the United States established in 1946. Deep ties such as FVEY enable greater information sharing and security, which allows for the distribution of sensitive knowledge, such as nuclear submarine designs. However, this depth of information sharing is rare. The United States would not be capable of making similar commitments to AUKUS in Japan or South Korea without significant changes to its information security infrastructure. As the AUKUS agreement develops, this unequal treatment of allies in the region may cause greater strife among Indo-Pacific partners.

Taiwan: The Limits of Strategic Ambiguity

The US has long maintained a policy of strategic ambiguity over the defence of Taiwan. This policy, codified in the Taiwan Relations Act, neither guarantees nor renounces US intervention if China invades, attacks or seeks to undermine the current governance of Taiwan. In 2024, the US authorised over USD2 billion in arms sales to Taiwan for defensive purposes, including selling advanced missile and air defence systems and radar systems to detect and defeat Chinese missiles. The US provides Taiwan with the capabilities to defend itself but lacks the equivalent political commitment. Current policy creates significant risks and challenges for the credibility of US extended deterrence in the Indo-Pacific.

One large fear in the US defence establishment is that China may miscalculate by underestimating US resolve, believing that it can seize Taiwan without significant consequences. Conversely, Taipei may overestimate the US's willingness to come to the defence of Taiwan. More liberal members of the Taiwanese political spectrum may declare independence, triggering a conflict that neither side desires.

Furthermore, the US policy of strategic ambiguity muddies the credibility of US extended deterrence in the region. Allies like Japan and South Korea see a lack of clarity regarding Taiwan and may question US commitments to their defence. This ambiguity could further erode trust and push regional powers to pursue more independent security solutions. Senior Japanese political leaders have publicly sought to reinforce US commitments to Taiwan. For example, in 2021, Japanese Prime Minister Shinzo Abe stated, “A Taiwan emergency is a Japanese emergency, and therefore an emergency for the Japan-US alliance.” While the policy of strategic ambiguity is intended to deter both Chinese aggression and Taiwanese moves toward independence, this ambiguity creates significant risks and challenges for US credibility and regional extended deterrence.

The US policy of strategic ambiguity creates significant credibility challenges for the US extended deterrence mission. However, abandoning this policy would dangerously escalate tensions in the region. Beijing views Taiwan as part of China, and a shift in US policy to explicitly defend Taiwanese independence may spark a direct military conflict between the US, China and Taiwan. The ultimate purpose of deterrence is to prevent war. The steps that policymakers take to strengthen the routine practice of deterrence should align with this goal.

Addressing the Gaps

Several factors contribute to the credibility challenge faced by the US in extending deterrence in Asia. China's growing military power and assertiveness have challenged US dominance in the region, raising concerns about its willingness to confront Beijing directly in a conflict involving its allies. The US policy of strategic ambiguity towards its extended deterrence commitments with Taiwan, deliberately leaving uncertainty about its response to an attack on Taiwan, contributes to doubts about its commitment to extended deterrence. Additionally, North Korea's relentless pursuit of nuclear weapons and missile technology has increased the perceived threat to US allies, raising doubts about whether Washington would risk a nuclear attack on its own soil to defend them.

To address this credibility challenge, the US needs a multifaceted approach:

• Strengthening Communication: Clear and consistent communication with allies is crucial to reassure them of the US commitment to their defence. This includes regular consultations, joint military exercises and public statements reaffirming the US security guarantee.
• Enhancing Capabilities: The US needs to maintain a robust military presence in the region and invest in advanced capabilities to deter potential adversaries. This includes modernising the US nuclear arsenal within the existing programme of record, deploying strategic assets and developing missile defence systems.
• Deepening Cooperation: Strengthening alliances and fostering cooperation with regional partners can enhance collective security and demonstrate the US commitment to regional stability. This includes initiatives like the Quad and the AUKUS partnership.
• Addressing Underlying Concerns: Addressing the root causes of regional tensions, such as North Korea's nuclear programme and territorial disputes in the South China Sea, can help reduce the perceived threat and enhance stability.

Conclusion

The US faces a growing credibility challenge in upholding extended deterrence in Asia. While the Washington Declaration and the AUKUS agreement are steps in the right direction, more needs to be done to reassure allies and to maintain stability. The incoming Trump administration will have to grapple with these challenges or face greater risks of proliferation and conflict. A comprehensive approach involving clear communication, enhanced capabilities, deeper cooperation and addressing underlying concerns is crucial to ensure the continued effectiveness of US extended deterrence in the region. Failure to do so could lead to a dangerous erosion of trust, potentially destabilising the regional security architecture and increasing the risk of proliferation and conflict.