What Allied ultimatum did Japan accept when ending World War II?

Japan accepted the Potsdam Declaration when it agreed to end World War II.

Issued on July 26, 1945, the declaration called for the unconditional surrender of Japan's armed forces. It was issued by United States President Harry Truman, British Prime Minister Winston Churchill, and Chinese leader Chiang Kai-shek during the Potsdam Conference.

The declaration warned Japan that refusal would bring “prompt and utter destruction.” Japan's government eventually accepted its provisions, with the status of the emperor addressed through later Allied communications. Hirohito referred to acceptance of the declaration in his August 15 broadcast.

The Potsdam Declaration should not be confused with the Cairo Declaration of 1943, which discussed Allied aims concerning Japan and territories seized by Japanese expansion. The Instrument of Surrender later formalized Japan's acceptance and set the legal framework for ending hostilities.