Unit 731 was a covert biological and chemical warfare research and development unit of the Imperial Japanese

Unit 731 was a covert biological and chemical warfare research and development unit of the Imperial Japanese Army that undertook lethal human experimentation during the Second Sino-Japanese War (1937–1945) and World War II.

It was responsible for some of the most notorious war crimes carried out by Japanese personnel.Some of the numerous atrocities committed by the commander Shiro Ishii and others under his command in Unit 731 include: vivisection of living people (including pregnant women who were impregnated by the doctors), prisoners had limbs amputated and reattached to other parts of their body, some prisoners had parts of their bodies frozen and thawed to study the resulting untreated gangrene.

Humans were also used as living test cases for grenades and flame throwers. Prisoners were injected with strains of diseases, 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 via rape, then studied. Having been granted immunity by the American Occupation Authorities at the end of the war, Ishii never spent any time in jail for his crimes and died at the age of 67 of throat cancer.

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