Unit 731 was a covert development unit of the Imperial Japanese Military that was responsible for covert biological and chemical warfare research that used people for shocking experimentation during the Second Sino-Japanese War and World War II. The unit conducted the most notorious war crimes performed by any Japanese personnel.
The unit was stationed at the Pingfang district of Harbin, the largest city in the Japanese puppet state of Manchukuo (now Northeast China).
It was officially known as the Epidemic Prevention and Water Purification Department of the Kwantung Army. Originally set up under the Kempeitai military police of the Empire of Japan, Unit 731 was taken over and commanded until the end of the war by General Shiro Ishii, an officer in the Kwantung Army. The facility itself was built between 1934 and 1939 and officially adopted the name “Unit 731” in 1941.
It is estimated that around 3-12,000 men, women, and children, died during the human experimentation conducted by Unit 731 at the Pingfang base alone, and excludes victims who died during experiments from other medical camps.
Nearly 70 percent of the people who died at the Pingfang camp were Chinese civilians and army personnel. While the other 30 percent was made up by Russians.
Most of those who worked for Unit 731 as researchers went on to have successful careers after the war in politics, business, and medicine. A lot were arrested by the Soviets and tried at the Khabarovsk War Crime Trials in 1949, but the majority were protected by American Forces during occupation.
The researchers under American Forces occupation were never tried for war crimes by America which allowed the intelligence gained in bio-weapons could be co-opted into the U.S. biological warfare program.
On 6 May 1947, Douglas MacArthur, as Supreme Commander of the Allied Forces, wrote to Washington that “additional data, possibly some statements from Ishii probably can be obtained by informing Japanese involved that information will be retained in intelligence channels and will not be employed as ‘War Crimes’ evidence.”
The immunity deal concluded in 1948.