Following V-J Day, or 'Victory in Japan Day' on August 14, 1945, the Allies assumed control of all Japanese territory. This included the Korean peninsula, which was divided at the 38th parallel between the zones of Soviet and American occupation. Unable to reach an agreement over a permanent government structure for Korea despite intervention from the United Nations, the Republic of Korea, also known as South Korea, was formed in August 1948, while the Democratic People's Republic of Korea, or North Korea, was formed a month later.

Allied occupation of Japan began on V-J Day, and lasted until 1952. American General Douglas MacArthur was appointed supervisor of the occupation by President Truman, and he effectively became the viceroy of Japan. Under his leadership, Japan was democratized and liberalized through land reform and other methods of social and economic restructuring. In May 1947, the new Constitution of Japan was enacted, reducing the emperor to a purely symbolic figure holding no real power. It also forbade Japan from settling international disputes through war. Generally, the liberally-reconstructed Japanese government was welcome by the Japanese people who were eager for change.