Continuity and changes: the effects of Russia’s war against Ukraine on Japanese and South Korean nuclear-weapons discourse

This article examines the continuity and changes in Japanese and South Korean discourses on nuclear weapons since Russia’s full-scale invasion of Ukraine in February 2022. While Japan experienced significant changes in its national-security policies, its discourse on nuclear weapons remained largely unchanged. In contrast, South Korea underwent notable shifts in its discourse on nuclear weapons in response to the evolving North Korean nuclear threat—an evolution that became evident after the start of the war in Ukraine. While the presence or absence of norms against nuclear weapons in the two countries may seem to provide a straightforward explanation for these outcomes, the article demonstrates that strategic factors are significant in both cases. These factors include the threat intensity posed by the primary external adversary and the envisaged type of external aggression. Specifically, Japan has maintained a distance from nuclear options and focused on reinforcing its conventional capability to counter a nonexistential threat from China and the risk of aerial or naval aggression. In contrast, South Korea has engaged in active discussions regarding diverse nuclear-deterrent options to hedge against an existential threat from North Korea and the risk of a ground attack.