When did the Allied occupation of Japan officially end after World War II?

The Allied occupation of Japan officially ended on 28 April 1952, when the Treaty of San Francisco entered into force.

Japan had formally surrendered in September 1945, but surrender did not immediately restore full sovereignty. The postwar occupation continued while the Allied authorities implemented demilitarization, political reforms, economic changes, and a new constitutional order.

The Treaty of San Francisco, also called the Treaty of Peace with Japan, was signed on 8 September 1951. When it took effect on 28 April 1952, Japan regained sovereignty and the occupation ended for most of the country. The treaty also ended Japan’s legal state of war with many Allied powers and set terms concerning former Japanese territories.

This date is distinct from 2 September 1945, the date of the surrender signing, and 3 May 1947, when Japan’s postwar constitution took effect. Okinawa and several other islands remained under separate U.S. administration for longer before later reversion arrangements.