During the Second World War, the Japanese Imperial Army carried out medical experiments on prisoners in occupied Manchuria. Unit 731, led by microbiologist Shiro Ishii, developed biological weapons, relying mainly on insects as disease carriers, including plague-infected fleas.
Estimates of Chinese victims vary widely. Some historians cite around 580,000 deaths, while others stress that exact figures cannot be established, as epidemics blended with war, famine and endemic disease.
After Japan's defeat, Ishii and several collaborators avoided war crimes prosecution in exchange for their experimental data. Only twelve members of the network were tried, by the Soviets, in Khabarovsk in 1949. Several former members later continued careers in Japanese medical research.
