East Asia in the aftermath of the Cold War might provide the most favorable case for realist theory due to historical rivalries, territorial disputes, economic competition, great power politics and deep-rooted realist beliefs among politicians in the region. Yet the fundamental realist prediction of balance of power in the region has not materialized. Neither internal nor external balancing in their original senses is explicitly present. This poses a serious challenge to realism and more broadly, western international relations theories for understanding regional dynamics. Several explanations have been put forward in previous research, such as a total rejection of the applicability of realism for explaining East Asian politics, modifying realism by adding new variables, and focusing on domestic variables. Using a neoclassical realist term, underbalancing, this dissertation goes beyond neoclassical realist theory of underbalancing by reintroducing the distinction between external and internal balancing, which has direct implications for the resources needed for a balancing policy and external reactions to balancing policy. In particular, this approach emphasizes the effect of interaction between states on underbalancing. By doing so, it also highlights what is omitted by realism, namely, the agency of the targeted state at risk of being balanced. In other words, the policy of the state that is aware of its risk of being balanced could draw upon foreign policy tools it possesses to neutralize the balancing efforts from others. This notion of state policies influencing the outcome of balance of power is tested with post-Cold War East Asian politics. The cases included China-Japan and China-ASEAN strategic interactions after the Cold War. Based on materials from public media outlets, official documents and recently leaked U.S. diplomatic cables, this dissertation argues that China's policies towards neighboring states- policies expressed variously through cultural, diplomatic, economic and security initiatives- are indispensable to explain the fact of underbalancing in the region.