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The Japanese unit responsible for human experimentation during World War II was Unit 731, officially named the Epidemic Prevention and Water Purification Department of the Kwantung Army. Led by Lieutenant General Shirō Ishii, it operated primarily in the Pingfang district of Harbin, in Japanese-occupied Manchukuo (Northeast China), from 1936 to 1945.


Purpose: Unit 731 was a covert biological and chemical warfare research unit of the Imperial Japanese Army. Its primary goal was to develop biological weapons (e.g., plague, anthrax, cholera) and study their effects on humans, often with the intent of deploying them against Chinese civilians and Allied forces. It also conducted experiments to understand human limits under extreme conditions.

Location and Scale: Based in a sprawling complex in Harbin, the unit included over 150 buildings and employed around 3,000 personnel, including scientists from Japan's top universities. It had the capacity to hold 600 prisoners at a time for experiments. Additional branches operated across China and Southeast Asia.

Victims: An estimated 3,000 to 12,000 men, women, and children—mostly Chinese prisoners of war and civilians, but also Koreans, Russians, and some British and American POWs—were killed in experiments at the Pingfang facility alone. Up to 200,000 may have died from biological weapons deployed in Chinese cities, such as plague-infected fleas dropped on villages.

Types of Experiments
Unit 731's experiments were notoriously inhumane, often conducted without anesthesia, and included:
Pathogen Testing:
Frostbite and Hypothermia:
Weapons Testing:
Syphilis and Rape:
Extreme Conditions:
Vivisection and Organ Removal:

Post-War Cover-Up
U.S. Immunity Deal: After Japan's surrender in 1945, the U.S., led by General Douglas MacArthur, granted immunity to Ishii and other Unit 731 scientists in exchange for their research data, which was deemed valuable for the U.S. biological weapons program at Fort Detrick, Maryland. No Unit 731 members were prosecuted at the Tokyo War Crimes Trials, unlike Nazi doctors at Nuremberg.


Soviet Trials: The Soviet Union prosecuted some Unit 731 members at the 1949 Khabarovsk War Crime Trials, but these were dismissed by the West as "communist propaganda."

Delayed Acknowledgment: Japan denied Unit 731's existence until 1984 and did not officially acknowledge it until 1998, with no formal apology issued. In 2018, Japan released the names of 3,607 Unit 731 members, increasing public awareness.

Yes, Unit 731 personnel did teach at medical schools post-war, with confirmed examples including Kozō Okamoto (pathologist, became a professor) and Tachiomaru Ishikawa (professor at Kanazawa University). Many others, facilitated by the U.S. immunity deal, joined institutions like the University of Tokyo and Kyoto University, leveraging their wartime expertise.