SCAP identified the Supreme Commander for the Allied Powers during Japan’s postwar occupation.
The title was created at the start of the occupation on August 14, 1945, as Japan’s surrender became imminent. General Douglas MacArthur held the position and directed the U.S.-led Allied occupation of Japan.
SCAP can refer both to the commander and, in common usage, to the occupation headquarters and its administrative apparatus. In Japan, the headquarters was often called GHQ, short for General Headquarters, which is why the two abbreviations are sometimes confused.
MacArthur issued directives affecting demilitarization, political reform, education, and Japan’s new constitutional order. He remained SCAP until President Harry Truman relieved him in April 1951.