INTERACTION BETWEEN Japan and Korea offers a vexing anomaly for the Realist school of international relations. This dominant school of thought essentially views state behavior under the anarchic conditions of the international system to be the product of factors such as relative military and economic capabilities, threats to external security, geography, and ideology. 1 In the case of the relationship between Japan and Korea throughout the cold war, both states were staunch allies of the United States and sites of the greatest concentrations of American military forces in East Asia. For most of the postwar era Japan and Korea have faced hostile Communist adversaries in China, the Soviet Union, and North Korea. Under U.S. patronage they have espoused generally similar liberal-democratic aspirations, although the extent and success of democratization processes in the two countries differed ( Japan's adoption of democratic governance being both earlier and more successful than Korea's). They have led East Asia with their exemplary postwar market economies based on state-guided industrialization and exportoriented strategies. Their high volume of bilateral trade and investment not only attests to the interdependence of their economies but also has fostered the creation of numerous domestic groups with strong interests in congenial relations. Geographic proximity and cultural familiarity also facilitate travel, communication, and policy coordination.
Given this general commonality of friends, enemies, political values, and economic systems, logic as well as a simple application of balance- of-threat theory suggests that cooperative relations should ensue. If states balance against threats, defined in terms of aggregate power, geographic proximity, offensive capabilities, and aggressive intentions, then Japan-ROK relations in the face of proximate Soviet, Chinese, and North