What was the Allied ultimatum that set the terms for Japan’s surrender in 1945?

The Allied ultimatum that set the terms for Japan’s surrender was the Potsdam Declaration.

The United States, United Kingdom, and China issued it on July 26, 1945, during the Potsdam Conference in Germany. It called for the unconditional surrender of all Japanese armed forces and warned of “prompt and utter destruction” if Japan refused.

The declaration outlined postwar conditions, including the occupation of selected Japanese territory, disarmament, punishment of war criminals, and the removal of leaders associated with militarism. It also stated that Japanese sovereignty would be limited to the main islands and other islands designated by the Allies.

The Soviet Union did not initially sign the declaration because it was still neutral toward Japan. After Japan accepted the terms, the Japanese Instrument of Surrender formally incorporated the declaration. Japan’s acceptance was announced on August 15, while the legal signing occurred on September 2.