Supreme Commander for the Allied Powers 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 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 Diet then ratified after a few amendments . Australian , British , Indian , Canadian , 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 Shogun style government which Japan was ruled under until the start of the Meiji Restoration Period . Immunity given to Imperial family and bacteriological research units members . Douglas MacArthur and his SCAP staff played a primary role to exonerate Emperor Shōwa ( Hirohito ) and all members of the imperial family implicated in the war such as Prince Chichibu , Prince Tsuneyoshi Takeda , Prince Asaka , Prince Higashikuni and Prince Hiroyasu Fushimi from criminal prosecutions before the Tokyo tribunal . As soon as 26 November 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 gave immunity to Shiro Ishii and all members of the bacteriological research units in exchange for germ warfare data based on human experimentation . On 6 May 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 popular 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 . " Apology rebuffed . Toward the end of the occupation , Emperor Hirohito let it be known to SCAP that he was prepared to apologize formally to U . S . Gen . MacArthur for Japan ' s actions during World War II – including an apology for the December 7 , 1941 attack on Pearl Harbor . Patrick Lennox Tierney had an intimate perspective on events which unfolded in SCAP headquarters . Tierney ' s office was on the fifth floor of the Dai - Ichi Insurance Building in Tokyo , the same floor where MacArthur ' s suite of offices was located . He was there on the day the Emperor came to offer this apology ; but when the emperor arrived , MacArthur refused to admit him or acknowledge him . A pivotal moment passed . Many years later , Tierney made an effort to explain his understanding of the significance of what he had personally witnessed : " Apology is a very important thing in Japan . " Issues which might have been addressed were allowed to remain open , and consequences unfolded across the decades which followed . Media censorship . 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 . End of SCAP . 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 . With the Treaty of San Francisco , the post of SCAP lapsed .