Abstract: On June 25, 1950, the outbreak of the Korean War brought a turning point to Japan, which was still immersed in the mood of defeat. The United States urgent participation in the war made it necessary to rely on Japans war resources and to re-evaluate Japans strategic value. Additionally, the signing of the “Treaty of Peace with Japan” and the U.S.-Japan Security Treaty relieved Japans worries about its future to promote the “Yoshida Line”. Furthermore, the rapid left turn and failure of the Japanese Communist Party during the war greatly weakened the left-wing forces in Japan, paving the way for the rapid development of capitalism. In the face of the first war crisis in East Asia after World War II, Japan took full advantage of the situation to quickly complete the transition to a normal country and embarked on the fast track of economic development. It can be said that Japan was the biggest winner in the entire Korean War. To trace the root of Japans rapid post-war recovery, it is necessary to make a multidimensional examination of the role Japan played in the Korean War and the opportunities it faced.

Key words: Korean War, Japans rearmament, “Treaty of Peace with Japan”, Japanese Communist Party, Japanese revival