The Supreme Commander for the Allied Powers (SCAP) (originally briefly styled Supreme Commander of the Allied Powers) was the title held by General Douglas MacArthur during the Allied occupation of Japan following World War II.
In Japan, the position was generally referred to as GHQ (General Headquarters), as SCAP also referred to the offices of the occupation, including a staff of several hundred U.S. civil servants as well as military personnel. Some of these personnel effectively wrote a first draft of the Japanese Constitution, which the National Diet then ratified after a few amendments. Australian, British, Indian, and New Zealand forces under SCAP were organized into a sub-command known as British Commonwealth Occupation Force.
These actions led MacArthur to be viewed as the new Imperial force in Japan by many Japanese political and civilian figures, even being considered to be the rebirth of the shōgun-style government which Japan was ruled under until the start of the Meiji Restoration. Biographer William Manchester argues that without MacArthur's leadership, Japan would not have been able to make the move from an imperial, totalitarian state, to a democracy. At his appointment, MacArthur announced that he sought to "restore security, dignity and self-respect" to the Japanese people.
One of the largest of the SCAP programs was Public Health and Welfare, headed by U.S. Army Colonel Crawford F. Sams. Working with the SCAP staff of 150, Sams directed the welfare work of the American doctors, and organized entirely new Japanese medical welfare systems along American lines. The Japanese population was physically badly worn down, doctors and medicines were very scarce, sanitary systems had been bombed out in larger cities. His earliest priorities were in distributing food supplies from the U.S. Millions of refugees from the defunct overseas Empire were pouring in, often in bad physical shape, with a high risk of introducing smallpox, typhus and cholera. The outbreaks that did occur were localized, as emergency immunization, quarantine, sanitation, and delousing prevented massive epidemics. Sams, who was promoted to Brigadier General in 1948, worked with Japanese officials to establish vaccine laboratories, reorganize hospitals along American lines, upgrade medical and nursing schools, and bring together Japanese, international, and U.S. teams that dealt with disasters, child care, and health insurance. He set up an Institute of Public Health for educating public health workers and a National Institute of Health for research, and set up statistical divisions and data collection systems.
SCAP arrested 28 suspected war criminals on account of crimes against peace, but it did not conduct the Toyko trials; the International Military Tribunal for the Far East handled that. President Harry Truman had negotiated Japanese surrender on the condition the Emperor would not be executed or put on trial. SCAP carried out that policy.
As soon as November 26, 1945, MacArthur confirmed to admiral Mitsumasa Yonai that the emperor's abdication would not be necessary. Before the war crimes trials actually convened, SCAP, the IPS and Shōwa officials worked behind the scenes not only to prevent the imperial family being indicted, but also to slant the testimony of the defendants to ensure that no one implicated the Emperor. High officials in court circles and the Shōwa government collaborated with Allied GHQ in compiling lists of prospective war criminals, while the individuals arrested as Class A suspects and incarcerated in Sugamo Prison solemnly vowed to protect their sovereign against any possible taint of war responsibility.
As Supreme Commander for the Allied Powers, MacArthur also decided not to prosecute Shiro Ishii and all members of the bacteriological research units in exchange for germ warfare data based on human experimentation. On May 6, 1947, he wrote to Washington that "additional data, possibly some statements from Ishii probably can be obtained by informing Japanese involved that information will be retained in intelligence channels and will not be employed as "War Crimes" evidence." The deal was concluded in 1948.
According to historian Herbert Bix in Hirohito and the Making of Modern Japan, "MacArthur's truly extraordinary measures to save the Emperor from trial as a war criminal had a lasting and profoundly distorting impact on Japanese understanding of the lost war."
Above the political and economic control SCAP had for the seven years following Japan's surrender, SCAP also had strict control over all of the Japanese media, under the formation of the Civil Censorship Detachment (CCD) of SCAP. The CCD eventually banned a total of 31 topics from all forms of media. These topics included:
Although some of the CCD censorship laws considerably relaxed towards the end of SCAP, some topics, like the atomic bomb, were taboo until 1952 at the end of the occupation.
MacArthur was succeeded as SCAP by General Matthew Ridgway when MacArthur was relieved by President Harry S. Truman during the Korean War in April 1951. When the Treaty of San Francisco came into effect on April 28, 1952, the post of SCAP lapsed.