Abstract
Since the end of the Cold War, Japan’s acceptance and institutionalization of a non-combat military role to aid the US has led to its new identity as a US ally and has transformed the content of its ‘peace state’ identity. It is this role that has made these two identities more compatible. This article first attempts to measure the long-term shift in Japan’s two identities by conducting a content analysis of Japan’s Defence White Papers and then seeks to trace the formation process of Japan’s dual security identity through which it accepted and institutionalized a non-combat military role. For this analysis, the process is divided into three stages: the Cold War period when its two identities as a ‘peace state’ and a US ally were considered incompatible, the period of the 1990s when Japan started to accept and institutionalized a non-combat military role, and the period after 11 September 2001 when Japan’s dual security identity gradually got established. In the final section, the article discusses the source of a security identity shift in Japan and draws some implications for the future of its security policy.