Unit 731 (731部隊) was a covert biological warfare research and development unit of the Imperial Japanese Army that undertook human experimentation mainly on Chinese, Koreans and Russians, during the Second Sino-Japanese War (1937–1945) and World War II, led by infamous Japanese microbiologist Shiro Ishii.
At least 12,000 men, women, and children were murdered during the experimentation conducted by Unit 731 at the camp based in Pingfang alone. Prisoners of war were subjected to vivisection without anesthesia. Vivisections were performed on prisoners after infecting them with various diseases. Scientists performed invasive surgery on prisoners, removing organs to study the effects of disease on the human body. These were conducted while the patients were alive because it was feared that the decomposition process would affect the results. Human targets were used to test grenades positioned at various distances and in different positions. Flame throwers were tested on humans. Humans were tied to stakes and used as targets to test germ-releasing bombs, chemical weapons, and explosive bombs. Prisoners were injected with inoculations of disease, disguised as vaccinations, to study their effects. To study the effects of untreated venereal diseases, male and female prisoners were deliberately infected with syphilis and gonorrhea, then studied. Prisoners were infested with fleas in order to acquire large quantities of disease-carrying fleas for the purposes of studying the viability of germ warfare. Plague fleas, infected clothing, and infected supplies encased in bombs were dropped on various targets. The resulting cholera, anthrax, and plague were estimated to have killed around 400,000 Chinese civilians. Tularemia was tested on Chinese civilians (Source: Wikipedia)