731

731, commonly known as Unit 731, was a covert biological and chemical warfare unit of the Imperial Japanese Army. It operated mainly in occupied Manchuria (northeast China) from the early 1930s until the end of World War II. The unit was headquartered in Pingfang, near Harbin, and was part of the Kwantung Army. It was led by General Shiro Ishii and pursued through public health rhetoric a program of research, development, and dissemination of biological agents.

The activities of Unit 731 included extensive human experimentation and weapons testing. Subjects were primarily Chinese civilians, along with prisoners of war and others, often without consent. Experiments involved infections with plague, cholera, anthrax, smallpox, and other pathogens, as well as vivisections, frostbite and hypothermia tests, and chemical exposures. The unit also conducted field and combat testing of biological weapons, including attempts to gauge the spread and effectiveness of agents under various conditions.

Victims and impact: estimates of those affected by Unit 731’s activities vary widely, with scholarly estimates often placing the direct number of victims in the tens of thousands. The broader toll of the unit’s activities intersected with ongoing warfare and occupation across China and other territories.

After Japan’s surrender, the fate of Unit 731 personnel was marked by limited prosecutions and, in some cases, secrecy. Some members were granted immunity in exchange for data gathered from experiments, and detailed records remained restricted for many years. The legacy of Unit 731 has made it one of the most infamous examples of wartime medical and biological wrongdoing, influencing international discussions on ethics in research and the enforcement of war crimes.