During the Cold War, Japan and the Soviet Union were located on opposite sides of the bipolar divide. While Japan served as the principal base for US force projection in Asia, the Soviet Union was at the head of a communist bloc that included North Korea, Vietnam, Laos and, at least initially, China. This geopolitical situation ensured frosty bilateral relations. Nowhere was this more apparent than in Japan’s Cold War defense strategy, which considered naval action by the Soviet fleet and invasion of Hokkaidō by Soviet motorized rifle divisions as the principal threats to national security.