By William Purdy, Fall 2024 Marcellus Policy Fellow

The United States has long prided itself on its defensive alliances with both Japan and South Korea. As a staunch ally offering its nuclear umbrella to protect both countries, the United States has provided significant resources to their defense and protection for over 75 years. As challenges to these alliances mount, especially a worsening American debt crisis and regional security crises, the United States must begin a reevaluation of its East Asian security commitments. Both the Japanese and the South Koreans have long advocated for a reduced American presence in their domestic politics but have lagged behind in critical military technology that the United States possesses a monopoly on such as stealth aircraft, blue water naval vessels, and most importantly, nuclear weapons.

In an era of increased revisionism from adversaries such as Russia, North Korea, and China, and the potential for American abandonment in a conflict under President Donald Trump, Japan and South Korea will soon come to a twilight moment of whether to invest into nuclearization or risk being at the mercy of nuclear coercion at the hands of these regional threats. This is compounded by the United States bearing the financial cost of a combined $34.3 billion spent between the stationing of troops in Japan and South Korea from 2016-2019. The inordinate cost of the nearly 80,000 American personnel there has prompted concern from notable politicians such as President Trump, who question the cost-benefit calculus of defending these two countries. As this relationship is reconsidered under a second Trump presidency, this paper will provide a framework for the current total cost of U.S. force deployments, the nuclearization costs for both Japan and South Korea, and dive into how nuclearization can affect the region.

In a leadup to potential nuclearization by Seoul or Tokyo, the United States has a plethora of options to enable these allies to develop nuclear weapons. By adopted a pragmatic approach to sanctions, extended nuclear deterrence, and shifting politics, the United States can effectively help these allied nations sprint towards a nuclear weapon as it sunsets defense obligations to them thereafter. By utilizing all elements of national power, a solution can be reached that provides regional stability to East Asia while simultaneously enabling American withdrawal.