“I cut him open from the chest to the stomach, and he screamed terribly, and his face was all twisted in agony. He made this unimaginable sound, he was screaming so horribly. But then finally he stopped. This was all in a day’s work for the surgeons, but it really left an impression on me because it was my first time.” These were the words of a former Unit 731 medical assistant in an interview published by the New York Times. He describes the process of deliberately infecting a Chinese prisoner with the plague and vivisecting him without anesthetics. Experiments like this were regular in Unit 731, one of Japan’s biological warfare research facilities.
Officially named the Epidemic Prevention and Water Purification Department of the Kwantung Army, the Imperial army formed Unit 731 in 1937 in the Pingfang district of Harbin. However, five years before Unit 731, the army had already begun creating their germ research facilities in Manchuria. Led by Ishii Shiro, a military doctor from the University of Kyoto, the unit researched the effects of various diseases such as the plague, anthrax, and typhoid. There are sources that state the original purpose of the research was to find cures and vaccines for diseases inflicting Japanese soldiers. However, others claim that the Ishii had intentions of producing biological weapons from the start. Nevertheless, in Unit 731, members researched the effects of biological weapons through human experiments of the cruelest nature.
Chinese prisoners made up the majority in Unit 731, though many Russian, Mongolian, and Korean captives were also present. Unit members called these prisoners Marutas, the Japanese term for logs, to dehumanize them.
Researchers rarely injected the prisoners directly with bacteria or viruses but instead used cultured fleas. They would expose the fleas to infected rats and place them in a ceramic bomb. Members would drop the bombs on prisoners from various distances and note the symptoms of the infections over time. As stated in the opening quote by the former medical assistant, researchers would vivisect the prisoners alive without anesthetics and extract the bacteria from the internal organs. They would note the speed and degree of the infection for each organ.
Research on sexually transmitted diseases was also conducted on female prisoners. Members would purposefully infect the prisoners via an injection or rape. The prisoners were forced to become pregnant to study the degree of infection for the babies.
The army began implementing biological weapons in the Second Sino-Japanese war. Notably, in the Zhejiang-Jiangxi campaign, Japanese soldiers released the bombs with plague-infected fleas into food and water supplies, causing an epidemic in the region. Victims would first notice blisters around their body, many on their legs. The blisters would turn into ulcerative skin lesions. Many also would experience severe fevers and pain. Most civilians could not afford effective treatments or medicine, leading to long-term conditions or death. These diseases would continue to pose a threat to generations after the war ended.
When the Soviets invaded Manchuria in 1945, Ishii and his units quickly began destroying the evidence. However, by the time the Americans got to Ishii, plenty was available to convict him of war crimes. But MacArthur and his American leaders agreed to exchange information collected in the units for the immunity of the members, including Ishii. However, some members were convicted by the Soviets in the Khabarovsk War Crime Trials. None of the imprisoned were executed but were subjected to hard labor. The Soviets published the content of the trial in 1950, but due to the tensions surrounding the Cold War, the U.S. dismissed such evidence, and it never reached a global audience. The nature of the crimes finally came to light in the 1980s when ex-members such as Ken Yuasa publicly admitted to their crimes.
Since the end of the war, the Japanese government has apologized for its crimes. However, they have never acknowledged specifics atrocities, including but not limited to Unit 731. Despite its lasting effects, most around the world know very little. There remains a lot of work to bring justice to those victims. Please consider spreading the word.
Chan, Jenny, et al. Seeking Justice for Biological Warfare Victims of Unit 731. Edited by Barbara Halperin, Pacific Atrocities Education, 2020.
Kristof, Nicholas D. “Unmasking Horror -- A Special Report.; Japan Confronting Gruesome War
Atrocity.” The New York Times, The New York Times, 17 Mar. 1995,
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