On V-J Day , US President Harry Truman appointed General Douglas MacArthur as Supreme Commander for the Allied Powers ( SCAP ) , to supervise the occupation of Japan . During the war , the Allied Powers had planned to divide Japan amongst themselves for the purposes of occupation , as was done for the occupation of Germany . Under the final plan , however , SCAP was given direct control over the main islands of Japan ( Honshu , Hokkaido , Shikoku , and Kyushu ) and the immediately surrounding islands , while outlying possessions were divided between the Allied Powers as follows : It is unclear why the occupation plan was changed . Common theories include the increased power of the United States following development of the atomic bomb , Truman 's greater distrust of the Soviet Union when compared with Roosevelt , and an increased desire to restrict Soviet influence in East Asia after the Yalta Conference
Yalta Conference
Yalta Conference
Occupation of Japan