The Japanese bioweapons program was the brainchild of Gen. Shirō Ishii, who in the 1930s received backing at the highest levels to form a biological warfare unit known as Unit 731, deceptively designated the “Epidemic Prevention and Water Purification Department” of the Kwantung Army deployed to China. Unit 731 established a massive 150-building complex in the Pingfang District of Harbin (then part of the puppet state of Manchuria), where it developed and tested its weapons on involuntary human subjects, around two-thirds of whom were Chinese, with most of the rest coming from the Soviet Union. Their subjects would later include a small number of Allied POWs, Koreans and Pacific islanders.