Unit 731, also known as the Demon Unit, was a secret military medical unit that was engaged in biological warfare and bacterial warfare research and human experiment research by the Japanese Army in Harbin, China during World War II. It was also the code name of the preparation factory.
They use living humans to do biochemical weapon effect experiments, such as vivisection, throwing grenades at people at different distances, frostbite, flame jet, plague, horse-to-human exchange blood, exchange of limbs, crossbreeding of humans and animals, etc. .
After the war, the US government pardoned the scientists responsible for these experiments and allowed them to arrive in the United States safely, saying that it was a return for their research findings.