Many political and military Japanese leaders were convicted for war crimes before the Tokyo tribunal and other Allied tribunals in Asia. However, all members of the imperial family implicated in the war, such as emperor Showa and his brothers, cousins and uncles such as Prince Chichibu, Prince Hiroyasu Fushimi and Prince Asaka, were exonerated from criminal prosecutions by Douglas MacArthur.

The Japanese military before and during World War II committed numerous atrocities against civilian and military personnel. Large scale massacres, rapes and looting against civilians were committed most notably the Sook Ching and Nanking massacre, and the use of around 200,000 "comfort women", who were forced to serve as prostitutes for the Japanese military.

The Imperial Japanese Army also engaged in the execution and harsh treatment of Allied military personnel and POWs and biological experiments were conducted by Unit 731 on civilians and prisoners of war; this included the use of biological and chemical weapons authorized by emperor Sh?wa himself. According to the 2002 International Symposium on the Crimes of Bacteriological Warfare, the number of people killed in Far East Asia by the Imperial Japanese Army germ warfare and human experiments was estimated to be around 580,000.[24] Shir? Ishii and all Unit 731 members received immunity from US General Douglas MacArthur in exchange for germ warfare data based on human experimentation.