Walking a Fine Line: US Involvement in Bilateral Tensions between South Korea and Japan

Abstract South Korea and Japan have maintained tense bilateral relations over their unresolved historical and territorial disputes for decades. The US has repeatedly called for improved relations between South Korea and Japan and underlined the importance of US–South Korea–Japan trilateral relations to address North Korean threats and regional security challenges. Would we, then, expect the US to play a role in helping to mediate South Korea–Japan problems? If so, under what conditions and to what extent would the US get involved in South Korea–Japan disputes? If not, what makes the US hesitate to do so? We argue that US involvement in South Korea–Japan bilateral relations depends on the degree to which the US perceives the tensions as costly and risky for US national security interests. With an issues-based analysis, a granular examination of South Korea–Japan trade disputes and the spat over the GSOMIA in 2019, and qualitative interviews with former US government and military officials, we find that the US is more likely to involve itself in South Korea–Japan relations and more likely to use its leverage as a major power with its allies when it perceives significant risks to its capabilities to address security challenges, primarily those posed by North Korea.