Understanding Japan–South Korea Cooperation and Friction Through Neoclassical Realist Theory

The relationship between Japan and the Republic of Korea (ROK) 1 1 Used interchangeably with ‘South Korea’. has largely eluded theoretical explanations as to why these two allies of the USA continue to share a volatile relationship. The friction between these countries has largely been attributed to their colonial past. The historical aspect is no doubt an indispensable factor contributing to a fractured relationship. However, historical animosity in itself cannot explain the causes behind intermittent friction and cooperation. Bilateral relations between the two countries do not follow balance of threat theory predictions either. Alliance theory states that states will ally against a common threat. Despite this, Japan and the ROK have failed to cooperate even when regional threat level was high. Here, Victor Cha's quasi-alliance theory potentially sheds light on the puzzle. It stresses on the role of a third-party patron and its level of commitment to each of its allies as a determining factor in cooperation or friction between the regional players. The purpose of this article is to test the predictions of this theory. The article tries to determine Japan and the ROK’s perception of US commitment during the Obama administration and the Trump administration, respectively. The next task is to ascertain whether Japan and ROK actions reflected the predictions of the theory. The article concludes on theory implications in the recent climate of bilateral volatility.