The Treaty of San Francisco entered into force on April 28, 1952, formally ending Japan’s state of war with most Allied countries.
The treaty was signed in San Francisco on September 8, 1951, by Japan and 48 countries. It restored Japanese sovereignty, established the framework for peace, and ended the Allied occupation when it took effect. The United States and many other former enemies became treaty partners rather than occupying powers.
This date is different from September 2, 1945, when Japan signed the surrender instrument and active hostilities ended. It is also different from August 15, 1945, when Hirohito announced Japan’s acceptance of the Allied terms. Those milestones marked surrender and the end of fighting, while the 1952 treaty dealt with the formal legal peace settlement.
The treaty did not resolve every relationship. The Soviet Union did not sign it, and Japan’s state of war with the Soviet Union ended separately through the Soviet-Japanese Joint Declaration of 1956.