Institutionalized Alliance and the Formation of Japan's Postwar Foreign and Security Policy: U.S. Influence and Japanese Choices

Following the end of World War II, Japan's foreign and security policy underwent a profound transformation, moving away from the prewar model of military expansion and toward a national strategy centered on pacifism, economic development, and reliance on the United States for security. In this process, the United States shaped Japan's postwar foreign and security structure through occupation reforms, the institutionalization of Article 9 of the Constitution, the security treaty system, the maintenance of U.S. forces, and the Okinawa arrangements. However, attributing this transformation primarily to external shaping by the U.S. fails to capture the full complexity of Japan's policy evolution. Japan was not merely a passive recipient of external arrangements; rather, it used the security guarantees provided by the United States within existing institutional constraints to limit its military burden and allocate resources toward economic development. Simultaneously, domestic factors such as pacifist norms, socio-political opposition, and a sense of sovereignty shaped the trajectory of post-war security policy and influenced the specific forms of U.S.-Japan security cooperation. Consequently, this paper examines the mechanisms through which U.S. influence, exercised through institutionalized alliance mechanisms, affected Japan's foreign and security policies between 1945 and 1972. This study demonstrates that Japan's postwar foreign and security policies were not simply shaped by the United States alone, but emerged from the interaction between U.S. strategic influence, Japanese policy choices, and domestic political norms. Although the United States provided the institutional security framework, Japan accepted, adapted, and reshaped this framework through domestic political and policy processes.