Indispensable, Yet Insufficient: Japan, South Korea, and the Conditional Diplomacy of Middle Powers from the Cold War to the Asia-Pacific Era

This chapter examines Japan and South Korea’s multilateral strategies from the Cold War to the Asia-Pacific era and their implications for regional order. During the Cold War, both pursued regional initiatives but were constrained by dependence on the United States, historical grievances, and domestic imperatives. Japan possessed capacity but lacked legitimacy, while South Korea sought legitimacy without capacity. These deficits produced fragmented institutions that contrasted with Europe’s dense regionalism. The post-Cold War era relaxed but did not remove these constraints. New frameworks such as APEC, the ASEAN Regional Forum, and ASEAN + 3 enabled Japan to assert leadership in economic governance and allowed democratized South Korea to emerge as a credible middle power. Yet U.S. dominance, China’s rise, and unresolved divisions kept East Asian regionalism fragile and consensus-based. Conceptually, the chapter reframes middle-power diplomacy as conditional and relational rather than inherent. Japan and South Korea promote norms, facilitate dialog, and contribute to areas such as finance, development, and climate diplomacy, but their influence remains limited and often overshadowed by great-power rivalry. This paradox of being “indispensable yet insufficient” illustrates both the potential and constraints of middle-power diplomacy in shaping regional order and stability in the Asia-Pacific.