Unit 731- Japan's Best-Kept Secret

by Lillian Hoffer

​Unit 731 was one of Japan's best kept secrets: a biological and chemical warfare research facility operated by the Japanese Imperial Army during World War II in occupied Manchuria. Victims included people of many backgrounds, such as Chinese, Koreans, Soviets, and others, subjected to vivisections, frostbite tests, germ weapon trials, and altitude experiments. Despite the scale of these atrocities, many perpetrators were granted immunity in exchange for data, allowing Unit 731 to remain one of history’s most disturbing and underreported war crimes.

Overview
Located in Japanese-occupied Manchuria, Unit 731 was disguised as a lumber mill to local civilians, hiding its true identity as a hub for biological warfare experiments. Victims were usually transported in the dead of night, “in crammed freight cars with lumber logs on top or were delivered in grayish-green paneled Dodge trucks owned by the Kempeitai.” Once inside the facility, they were smuggled underground by an underground tunnel through secret passages. According to witness Fang Shen Yu, “technicians in white coats handled the victims who were tied in bags so tightly that their head and feet touched each other.” This method was similar to that of the earlier Zhong Ma Complex, but on a much greater scale. 

Victims were often arrested on no grounds due to false charges of anti-Japanese sentiment. Many accusations included opium smoking, espionage, communism, mental disability, or homelessness, before being sent to Unit 731 for experimentation. Those captured included “Chinese, stateless White Russians, Harbin Jews, Soviet prisoners captured at the borders, Mongolians, Koreans, and Europeans accused of espionage.1” Major Iijima Yoshio admitted during the Khabarovsk Trials that he alone had subjected at least 40 Soviet citizens to experimentation. The Khabarovsk Trials were a series of public proceedings held by the Soviet Union in 1949 to prosecute twelve Japanese military officials, including physicians and researchers, for crimes against humanity, including biological warfare and human experimentation. Despite presenting credible evidence that the Japanese army had used biological weapons and conducted experiments on living subjects, the trials were largely dismissed by the United States as Eastern communist propaganda. Each prisoner was tagged with a number starting at 101 and ending at 1500. “Once 1500 was reached, they began again at 101, which made it impossible to determine how many actually fell victim to Unit 731.[1]” The terminology used by researchers to describe human subjects reflects the dehumanization intrinsic to the system. Unit 731’s scientific papers referred to people as “Manchurian monkeys,” “monkeys,” “Taiwan monkey,” and “Formosan monkey.” 
The violence was systemic, embedded in the facility’s culture. “As requested by the Command of the Japanese Air Force, Unit 731 also housed a pressure chamber to test the endurance of human organs at high altitudes. In this chamber, men died painful deaths.” These deaths were not anomalies but part of scheduled trials and studies, often for data related to weapon efficiency or survival limits. A firsthand account revealed, chillingly, that “children [were] forced into gas chambers.” One such child was “14 years old when he became assigned to Unit 731.”
The Anda Testing Grounds and Japan’s Biological Weapons Program
The Pingfan facility  functioned as Unit 731’s core, with atrocities extended to other locations such as the Anda Field Test Site, 140 kilometers north of Harbin, where most biological and chemical weapons testing occurred there. According to records, “Testing at Anda began as early as June 1941 when Unit 731 tested plague-infested flea bombs on humans.” Victims were “tied to stakes and used as targets to test germ-releasing bombs, chemical weapons and explosive bombs[2].” Anda was a hub for  experiments exposing victims to the plague, anthrax, and frostbite. As the war neared its end,  the Anda site was eventually destroyed by the Japanese in 1945 during  their attempt  to evacuate Manchuria to erase evidence. 
Within its first few years, Unit 731 employed only around three hundred people staffed with only fifty doctors on site. The program exponentially grew over the years. “By 1936, the organization had grown to about one thousand members… By the end of the war, Unit 731 facilities and branches alone employed an estimated twenty thousand doctors, researchers, and support personnel.[2]” Each team specialized in a different pathogen. Known divisions included the Aki Sadahan Team and Ejima Team (dysentery), Enoshima Team (frostbite), Ida Team (X-ray), Ishikawa Team (anthrax), Kasahara Team (viral research), Kusa-mihan Team (pharmacological research), Minatohan Team (cholera), Niki Team (serum), Noguchi Team (rickettsia/fleas), Okamoto Team (tuberculosis), Ota Team (plague), Setogawa Team (cholera), and Tabei Team (typhoid). The term “maruta,[2]” or “logs,” was informally used by staff to describe human subjects. This name was just another tool used to further dehumanize victims in the unit.  Though this was never an official term, its usage reveals the internal culture of objectification.


Firsthand Confessions 
Although official records and trials have surfaced, few firsthand confessions have emerged. One of the most memorable came from a former medic, although he was not stationed in Japan, his practices can give us an idea of the atrocities performed widespread across the Pacific. Akira Makino was only 22 years old when he was stationed in the Philippines between December 1944 and February 1945. He stated, “I had performed surgery and amputations on dozens of prisoners of war before they were executed.” Makino described that, as part of his training, “I had been ordered to conduct amputations, abdominal dissections, and other experiments on condemned men, women, and children, including two men who had been beaten unconscious for allegedly spying for the US.[3]” While most atrocities are recorded from Manchuria, Makino's experience in the Philippines demonstrates how widespread this brutality was. Experts noted that “Mr. Makino is the first to testify that similar atrocities took place in south-east Asia.[3]” Ken Yuasa, another medic, described how young doctors were often indoctrinated. Stationed just south of Harbin, he recalled joining fellow physicians to observe as “a prisoner was shot in the stomach, to give Japanese surgeons practice at extracting bullets.”[4] Violent displays were passed off as educational experiences in order to diminish the value of life and perpetuate the teaching of hatred and violence to desensitize doctors and normalize violence. 
U.S. Silence After the War
After Japan’s surrender, the U.S. chose to conceal Unit 731’s crimes, prioritizing biological warfare data over prosecution. In Germany, the U.S. led the Nuremberg Doctors’ Trial, but in Japan, “the U.S. played an equally key role in concealing biological warfare experiments and securing immunity for the perpetrators.” The most notorious example involved Colonel Murray Sanders, who conducted a nine-week investigation. In a 1983 interview, Sanders confessed he had been “deceived” as he reflected, “the interrogations…were too soon after the surrender. However, if the men who actually know the detailed results of the experiments can be convinced that your investigation is from a purely scientific standpoint, I believe that you can get more information. … I believe it will reassure any personnel…that you are not investigating ‘war crimes.[5]’” During World War II in Germany, the idea of "medical war crimes" was first introduced by the scientists who were examining the Nazi medical experiments. They were the ones who pushed the legal teams to treat these acts as crimes and to pursue legal action against those responsible. In Japan, it was the opposite: “the legal staff was independently seeking evidence to prosecute war crimes, and the scientists were instrumental in stopping them.[5]”
Conversely, the Soviet Union pursued justice through the 1949 Khabarovsk Trials, where twelve military personnel were tried, including Major Iijima Yoshio. The Soviet report was largely dismissed by the U.S. as propaganda. Modern historians, however, consider the trial’s evidence reliable. Despite the gravity of their crimes, the perpetrators received “relatively light sentences in comparison to their atrocities,  suggesting that “the Soviets, like the Americans, traded leniency for access to data.5” The postwar response underscores a bleak truth. As one source summarized, “Wartime exigency does more than simply prioritize national security over human rights. It urges toughness and decisiveness in decision-making, so that a moral blindness that would be seen as a deficiency in other times is instead seen as a virtue and a necessity.[5]”
Conclusion
Unit 731 stands as one of the most horrifying examples of how science, stripped of ethics and weaponized by ideology, can justify atrocities in the name of research. Its horrors rival those of Nazi experimentation, yet its victims remain largely nameless in history. To this day, Japan has issued no official apology. Textbooks omit or downplay Unit 731. Survivors are scarce. Most victims died nameless, numbered, or referred to only as “logs.” It is the responsibility of the present to carry forward the memory of those erased under the guise of science, nationalism, and silence.

Sources:
1. “Pacific Atrocities Education.” Pacific Atrocities Education, https://www.pacificatrocities.org/experiences-at-the-human-experimentation-complex.html/.
2. Rider, Dwight R. Japan’s Biological and Chemical Weapons Programs; War Crimes and Atrocities , 2014, mansell.com/Resources/Rider_Whos_Who_in_Japanese_BW_2018-10-09_IN_PROCESS--SEEK-PERMISSION-TO-USE.pdf. 
3. McCurry, Justin. “Japanese Veteran Admits Vivisection Tests on Pows.” The Guardian, Guardian News and Media, 27 Nov. 2006, www.theguardian.com/world/2006/nov/27/secondworldwar.japan. 
4. “Summary of Japanese War Crime Tribunal Sentencing of Japanese Personnel: Vivisection and Aburayama Incidents.” Fukuoka POW Camp #1 - Page 5, Mansell, 2005, mansell.com/pow_resources/camplists/fukuoka/fuk_01_fukuoka/fukuoka_01/Page05.htm#Vivisections.
5. Brody, Howard, et al. “U.S. Responses to Japanese Wartime Inhuman Experimentation after World War II.” Cambridge Quarterly of Healthcare Ethics : CQ : The International Journal of Healthcare Ethics Committees, U.S. National Library of Medicine, Apr. 2014, pmc.ncbi.nlm.nih.gov/articles/PMC4487829/.

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