Unit 731 was a covert biological and chemical warfare research and development unit of the Imperial JapaneseArmy that undertook lethal human experimentation during the Second Sino-Japanese War (1937–1945) of World War II. It was responsible for some of the most notorious war crimes carried out by Japan. Unit 731 was based at the Pingfang district of Harbin, the largest city in the Japanese puppet state of Manchukuo (now Northeast China).
Thousands of men, women and children interred at prisoner of war camps were subjected to vivisection, often without anesthesia and usually ending with the death of the victim. Vivisections were performed on prisoners after infecting them with various diseases. Researchers 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. The infected and vivisected prisoners included men, women, children, and infants.
Prisoners had limbs amputated in order to study blood loss. Those limbs that were removed were sometimes re-attached to the opposite sides of the body. Some prisoners' limbs were frozen and amputated, while others had limbs frozen, then thawed to study the effects of the resultant untreated gangrene and rotting.
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 also repeatedly subject to rape by guards