Supreme Commander for the Allied Powers

After the end of the Second World War, the Supreme Commander for the Allied Powers (SCAP) was established by the Allied Powers as the authority responsible for the occupation and governance of Japan, with the purpose of ensuring the implementation of the Potsdam Declaration. Occupation policy under SCAP was guided by the fundamental principles of demilitarization and democratization.

The Supreme Commander for the Allied Powers served as the highest authority of the occupation, and General of the Army Douglas MacArthur was appointed as the first Supreme Commander. On the basis of the Japanese Instrument of Surrender, the exercise of governing authority by the Emperor and the Government of Japan was placed under the supervision of the Supreme Commander. Although SCAP was formally an organization of the Allied Powers, in practice the United States played the predominant role in directing its operations.

Under the leadership of Supreme Commander MacArthur, a series of reforms were implemented, including the promulgation of a new constitution, the dissolution of the zaibatsu, land reform, and educational reform. Subsequently, against the backdrop of the outbreak of the Korean War and the expansion of the Cold War in Asia, occupation policy toward Japan gradually shifted toward an emphasis on economic recovery. MacArthur was relieved of his post as Supreme Commander in April 1951.

The Allied occupation of Japan under SCAP continued until April 1952, when Japan’s sovereignty was restored with the entry into force of the San Francisco Peace Treaty. Within Japan, the term “GHQ,” derived from General Headquarters, was widely used as a common name for the occupation authorities.