SCAP identified General Douglas MacArthur’s occupation command in Japan after the 1945 surrender.
SCAP originally stood for Supreme Commander for the Allied Powers, the title held by MacArthur during the United States-led occupation of Japan. The position was created on 14 August 1945, shortly before the surrender ceremony and the start of Japan’s postwar transition.
The term could refer both to MacArthur as the supreme commander and, in common usage in Japan, to his headquarters and occupation administration. Japanese officials often encountered the related abbreviation GHQ, short for General Headquarters. SCAP issued directives to Japan’s government and supervised major political, economic, and social reforms.
MacArthur remained in charge until the occupation ended in 1952, when the San Francisco Peace Treaty came into force. SCAP is sometimes expanded incorrectly as “Supreme Commander of the Allied Powers”; the official title used “for,” not “of.” The command also oversaw Allied occupation policy beyond the surrender ceremony itself, including demilitarization and the restructuring of Japanese institutions.