Unit 731 was a covert biological and chemical warfare research and development unit of the Imperial Japanese Army that engaged in lethal human experimentation and biological weapons manufacturing during the Second Sino-Japanese War (1937–1945) and World War II.
It was responsible for some of the most notorious war crimes committed by the Japanese armed forces. Unit 731 routinely conducted tests on human beings who were dehumanized and internally referred to as "logs". Experiments included disease injections, controlled dehydration, hypobaric chamber experiments, biological weapons testing, vivisection, amputation, and weapons testing. Surgeon General Shiro Ishii served as the director of Unit 731, and was later granted immunity in the International Military Tribunal for the Far East by the United States government in exchange for information and research for the U.S. biological warfare program.