The Treaty of San Francisco took effect on April 28, 1952, formally ending Japan’s war with most Allied countries.
The treaty was signed on September 8, 1951, at the War Memorial Opera House in San Francisco. Japan and 47 Allied nations signed it, although the Soviet Union, Poland, and Czechoslovakia did not sign. The agreement restored Japan’s sovereignty and established the legal framework for the postwar peace.
This date is different from September 2, 1945, when Japan signed the Instrument of Surrender. The surrender ended the active conflict, while the peace treaty created the formal legal settlement with most of the Allied powers. Japan’s separate state of war with the Soviet Union ended later through the 1956 Soviet–Japanese Joint Declaration.
The treaty also addressed Japan’s territorial renunciations and claims, but several territorial questions remained disputed. Its entry into force therefore marked a major postwar transition rather than a second surrender ceremony.