What official Allied title did Douglas MacArthur hold at Japan’s surrender ceremony?

Douglas MacArthur held the title Supreme Commander for the Allied Powers at Japan’s surrender ceremony.

MacArthur signed the Instrument of Surrender on September 2, 1945, aboard USS Missouri in Tokyo Bay. His title was commonly abbreviated as SCAP. He signed on behalf of the Allied powers, while Fleet Admiral Chester W. Nimitz signed as the United States representative.

MacArthur then directed the Allied occupation of Japan. He served as the principal authority over the occupation government, although Japan’s existing bureaucracy continued to operate under Allied supervision. The occupation introduced major political, legal, and economic reforms, including a new constitution that came into force in 1947.

MacArthur’s title was distinct from his earlier wartime commands. He had been commander of Allied forces in the Southwest Pacific Area, but SCAP was the occupation authority created for postwar Japan. He remained in Japan until 1951, when President Truman relieved him during the Korean War.