What title did General MacArthur hold while leading the Allied occupation of Japan after 1945?

General MacArthur held the title Supreme Commander for the Allied Powers, abbreviated SCAP, while leading the Allied occupation of Japan after 1945. The title referred to the occupation headquarters and to MacArthur’s authority over Japan’s defeated government.

SCAP began operating after the surrender and directed demilitarization, war-crimes prosecutions, and political, educational, and economic reforms. Japan’s existing ministries continued to function, but they operated under SCAP directives. MacArthur also supervised a new constitution, promulgated in 1946 and effective in 1947, which established parliamentary government and renounced war as a sovereign right.

The occupation was formally carried out by Allied powers, but the United States supplied most personnel and exercised dominant influence. MacArthur remained SCAP until 1951, when President Harry Truman relieved him during the Korean War. The occupation ended in 1952 when the Treaty of San Francisco entered into force, restoring Japan’s sovereignty.