The war crimes involved the Imperial Japanese Army and the Imperial Japanese Navy under Emperor Hirohito and were responsible for the deaths of millions . Historical estimates of the number of deaths which resulted from Japanese war crimes range from 3 to 14 million through massacre , human experimentation , starvation , and forced labor that was either directly perpetrated or condoned by the Japanese military and government . Some Japanese soldiers have admitted to committing these crimes . Airmen of the Imperial Japanese Army Air Service and Imperial Japanese Navy Air Service were not included as war criminals because there was no positive or specific customary international humanitarian law that prohibited the unlawful conduct of aerial warfare either before or during World War II . The Imperial Japanese Army Air Service took part in conducting chemical and biological attacks on enemy nationals during the Second Sino-Japanese War and World War II and the use of such weapons in warfare were generally prohibited by international agreements signed by Japan , including the Hague Conventions ( 1899 and 1907 ) , which banned the use of " poison or poisoned weapons " in warfare
human experimentation
Unit 731
Japanese war crimes