Throughout the postwar era Northeast Asian security has rested on the triangular defense network of the United States, Japan, and the Republic of Korea. While U.S. security treaties with Japan and the ROK have formed two stable legs of this triangle, the third leg has been at best tenuous. Explaining this enigmatic relationship is difficult for the Realist school of thought in international relations theory. Despite the existence of common enemies and generally common interests, Japan- ROK relations have been extremely volatile since 1965. While the prevailing explanation correctly highlights the undercurrent of ill will between the two states as a reason, this cannot systematically account for the alternating periods of contention and cooperation.
This book offers a theoretical model for Japan-Korea relations that looks at interaction within the context of a quasi-alliance game, consisting of two states that remain unallied but share a third party as a common ally. The model operates at the intersection between Realism's emphasis on adversarial threats and the quasi-alliance emphasis on actions of the third, or common, ally in determining state behavior. In particular it argues that Japan's and the ROK's fears of being abandoned or entrapped in their quasi-alliance relationship is a key causal variable for policy outcomes. Abandonment is defined as the anxiety that an ally may leave the alliance or may not provide support in contingencies where support is expected. Entrapment is defined as the concern that commitments to an alliance may end up being detrimental to security interests.
Two hypotheses were deduced for explaining conflict and cooperation. Hypothesis A maintains that, if relations between states reflect an