During the Cold War period, particularly after the outbreak of the Korean War in 1950, Japan's political and security relations with the People's Republic of China and Taiwan had to cope with the realities of “two Chinas,” with the history of the Japanese colonization of Taiwan and its military aggression in China compelling post-war Japan to assume basically “non-strategic” security orientation. The fundamental argument in this article is that Japan's de facto “two Chinas” policy throughout much of the post-war period was not the result of careful consideration of its security priorities, but was rather a choice by default.