Unit 731

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Aerial view of Unit 731 (Pingfang, Manchoukuo) taken in 1932.

Shiro Ishii

Disease Prevention and Water Supply Unit 731 was a very large Japanese biological warfare team, that primarily experimented on civilians of various ethnicities, mainly Russian and Chinese, but also Manchus, Mongolians, and others. It was part of the Kwantung Army (關東軍), which was the most prestigious of Japan's armies. It was located in Pingfang (平房区 or 平房區), in what was then Japanese Manchukuo (Manchuria) and is now part of China. It started operations in 1932 and continued through World War II. Victims at Pingfang included hapless civilians, common criminals, and alleged spies. From 1942-1945, more than 1000 Allied soldiers were also experimented upon by Unit 731 at a prisoner of war camp located in Mukden (now known as Shenyang, 沈阳). General Shirō Ishii (石井 四郎) was the mastermind, creator and leader of the unit.

The Unit 731 annual budget was larger than that of any Japanese university, and was reportedly as large as the total tax revenue of Manchoukuo.

The unit performed vivisections without anesthetic and conducted experiments in the field of biological warfare on their unfortunate victims. Other experiments on victims included frostbite treatment, syphilis experimentation (including rape and forced pregnancy), grenade testing, centrifuge testing, testing of flamethrowers, and other gruesome experiments. After the war ended the entirety of Unit 731 was given immunity by the United States in return for the unit's data. An estimated 3,000 prisoners were killed at Pingfang during the experiments, which left no prisoner alive. There were survivors at the Mukden camp, but attrition was very high.

Unit 731 also spread biological weapons over Chinese cities and against Chinese troops. These usually resulted in minor epidemics, but in the case of the 1942 Chekiang (Zhejiang-Jiangxi, 浙赣战役) campaign, "germs of cholera, dysentery, typhoid, plague, anthrax and paratyphoid were all used", and Chinese losses from disease were very high but "inestimable". Disease spread back to the Japanese army with casualties of more than 10,000.

A smaller Japanese army unit, also located in Manchuria, known as Unit 100 was also conducting germ warfare testing on prisoners. Unit 100 was operated under the Kempeitai, the Japanese military police. Two other units were involved in biological warfare research: Detachment Nami 8604 (or Unit 8604) and Detachment Ei 1644 (or Unit 1644). Unit 8604 was under the command of the Japanese Southern China Area Army, located in Canton (Guangzhou), China. Unit 1644 was located in Nanking, China and conducted human vivisections.

Post-war

“”From then on, a curtain of secrecy was lowered. Unit 731 was not part of the Tokyo War Crimes Tribunal. One reference to "poisonous serums" being used on the Chinese was allowed to slip by for lack of evidence. Lawyers for the International Prosecution Section gathered evidence which was sent directly to President Truman. No more was heard of it. The Tokyo War Crimes Trials lasted from 1946 to 1949. These were not the only trials of Japanese war criminals, but they were the primary ones. The Americans took the view that all this valuable research data could end up in the hands of the Soviets if they did not act fast. This was, after all, the kind of information that no other nation would have had the ruthlessness to collect.

Japanese activity in the area of biological warfare was strongly suspected by the US as early as 1939, and the first public documentation of Japanese biological weapons was on April 9, 1942 with a thorough report by Dr. P. Z. King that was published in July 1943 in The China Handbook (pp. 679-682).

Towards the end of the war, the Soviet Union invaded Manchuria (under the terms of the Yalta Conference between the Allied Powers) and captured a few key personnel from Unit 731. Other members of the unit eventually managed to return to Japan, often secretly. The Pingfang site was found in near total destruction, having been destroyed by Unit 731 before the advance of Soviet troops. Almost all of the documents were destroyed by the unit.

The Tokyo War Crimes Trials took place during 1946 to 1948. They were not the only war crime trials of the Japanese, but they were the primary trials. Despite having copious evidence of biological warfare having been conducted by the Japanese, no charges were filed against members of Unit 731. The United States government had contact with Unit 731 members in Japan and interviewed them extensively, including Ishii. General Douglas MacArthur (who was then the Supreme Commander for the Allied Powers in Japan) gave immunity to Ishii and all other members of the unit. The Soviet Union had repeatedly asked that Ishii and the other members of Unit 731 located in Japan be tried as war criminals, but they had little influence within Japan. Among the enormous amounts of documents presented at the Tokyo War Crimes Trials, only brief — and perhaps accidental — mention was given to biological weapons.

In December 1949 in the border city of Khabarovsk, the Soviet Union tried and convicted 11 members of Unit 731 and one member of Unit 100. The trial was based on evidence from a few key documents and the confessions of those on trial. The trial was closed to Western observers. The prison sentences ranged from 2 to 25 years in a labor prison camp.

According to Kojima Takeo, a captain in the Shantung Army who spent time at Unit 731, he was among the 1050 prisoners who were considered war criminals and were sent to China from Russia in 1949 for further imprisonment. Not all of the prisoners were necessarily affiliated with Unit 731, but they all would have been captured in northern China.

The unpunished

Masaji Kitano

Why were the Unit 731 members, other than those captured by the Soviets, never tried? Both the Soviet Union and the US were keen to get as much information as possible on biological weapons. This was shown by the extensive interviews by US officials of Unit 731 members, the closed Khabarovsk trial, and the one-time joint interrogation of Ishii by the Soviets and the US (later denied by the Soviets). The United States wanted to obtain Japanese information about biological weapons and the only way to gain detailed information seemed to be to offer immunity. The Soviet trial at Khabarovsk showed that this was not necessarily the case, but a closed trial in Japan was probably not feasible. MacArthur's offer of complete and total immunity may have been excessively broad. The immunity, however, was a betrayal by MacArthur of his own troops, a few of whom were abandoned by MacArthur in the Philippines, and later transported to Mukden by the Japanese, winding up as guinea pigs for infection experiments. The Khabarovsk trial had been essentially dismissed by the US as a show trial by the Soviets, though it has now been established that the confessions and evidence reported from the trial were essentially completely accurate.

Many of the scientists and medical doctors of Unit 731 went on to have scientific careers after the war at universities, research institutes and pharmaceutical companies. Two important figures at Unit 731, Lieutenant-Colonel Ryoichi Naitō and Lieutenant-General Masaji Kitano founded a multinational company, the Green Cross Corporation, which would later be embroiled in a scandal for knowingly importing HIV-tainted blood into Japanese blood banks. Naitō even became a member of the New York Academy of Sciences.

The nearly-complete list of members of Unit 731 was finally revealed by the National Archives of Japan in 2018 after being petitioned by a group led by Katsuo Nishiyama, professor emeritus of Shiga University of Medical Science. The list of 3,607 members includes "52 surgeons, 49 engineers, 38 nurses and 1,117 combat medics".

The table below shows the activities before and after the war of unpunished members of Units 731, 100 and 1644, and of people who held academic positions that facilitated the units' activities. All information is based on Williams & Wallace and Gold. All positions during the war are at Unit 731 unless otherwise noted.

Name	Activity during the war	Position after the war
Shiro Ishii	Chief of Unit 731	Cambridge University lecturer Richard Drayton has claimed that Ishii served as a bioweapons consultant to the US military at Fort Detrick, Maryland. It was also alleged that he converted to Christianity and opened a free clinic for children in Japan. He died in 1959 from throat cancer.
Prince Tsuneyoshi Takeda (lieutenant colonel)	chief financial officer of the Kwantung Army (and therefore in charge of Unit 731 finances), observed poison gas experimentation on humans at Pingfan	Raised horses, started a failed business, was active in several International Olympics committees
Dr. Kiyoshi Asanuma	Identified the tick insect vector of epidemic hemorrhagic fever	Worked at the Research Institute for Natural Resources
Dr. Asahina	Assisted Dr. Asanuma	Chief of the Entomology Section of the Health and Welfare Ministry's Preventive Health Research laboratories
Dr. Ken'ichi Kanazawa	Performed tests on ticks	Chief of the research section of the Takeda Pharmaceutical Company
Dr. Kōji Andō	Headed the vaccine-producing laboratory at Dairen	Professor of Tokyo University's Infectious Diseases Research Institute
Dr. Tachiomaru Ishikawa	Pathologist	President at Kanazawa University's medical school
Professor Ren Kimura	Bacteriologist under whom Ishii studied, sent young medical graduates to Unit 731	Dean of Nagoya Municipal Medical School, won the Japan Academic Institute Prize, was a member of the New York Academy of Sciences (NYAS)
Dr. Masao Kusami	Leader of the pathology squad	Professor at the Showa University of Pharmacology
Dr. Tōru Ogawa	Researcher on typhoid and paratyphoid, Unit 1644	Professor, Faculty of Medicine, Nagoya City University
Kōzō Okamoto	Pathology squad leader at Pingfang, carried out human vivisection	Director of both the Kyoto University and Kinki University medical departments
Dr. Kazu Tabei	Researched dysentery, typhoid, and paratyphoid at Pingfang, fed typhoid to human experimentees	Professor of bacteriology at Kyoto University
Dr. Takeo Tamiya	"Talent scout" at Tokyo Imperial University	Dean of Tokyo Imperial University's Medical School, director of the Japanese National Cancer Centre, president of the Japan Medical Association
Dr. Yoshi Tsuchiya	Leader of diagnostic division in Nanking	Honorary professor at Juntendo University
Dr. Toshikazu Yamada	Director of a bacteriological unit	Professor of Kumamoto University, temporary director of Hygiene for the City of Yokohama
Dr. Taboku Yamanaka	Civilian technician at Nanking	Dean of Osaka Medical School
Dr. Hisato Yoshimura	Directed frostbite experiments on humans	President of Kyoto Prefectural Medical College, adviser to the Japanese Antarctic Expedition, President of the Japanese Meteorological Society, received the Order of the Rising Sun, Third Class, President of Kobe Women's University
Dr. Shinpei Ejima	Dysentery research	Joined the Japanese National Institute of Health (JNIH)
Major Dr. Jun'ichi Kaneko	Bomb expert	Joined the JNIH
Professor Saburō Kojima	Tokyo University Laboratory for Communicable Diseases, Director of the Den Ken research department, visited the Nanking human experimentation unit	Director of Second Division, National Institute of Health; worked in the Health and Welfare Ministry's National Preventive Health Research Centre
Lieutenant-General Yujirō Wakamatsu	Commander of Unit 100	Studied streptococcal infections in children at the JNIH
Dr. Yukimasa Yagisawa	Plant disease expert	Secretary of the Japanese Penicillin Association who worked at JNIH
Dr. Kiyoshi Hayakawa	Attempted to obtain yellow fever virus samples from the US before the war, member of the Singapore Detachment	Manager of the Hayakawa Medical Company
Colonel Tomosada Masuda	Ishi's deputy	General medical practice in Chiba Prefecture
Dr. Hideo Futaki	Headed the tuberculosis research squad, vivisection team leader	Co-founded Green Cross with Naitō & Kitano, President of S. J. Company
Colonel Dr. Kiyoshi Ōta	Military surgeon, led the raid on Changteh	General medical practice in Yamaguchi Prefecture
Dr. Masahiko Takahashi	Pingfang's leading plague researcher	General medical practice in Chiba Prefecture
Lieutenant Shunichi Suzuki	Accounting department in the Shansi detachment, later acknowledged that he knew of the unit's activities	Governor of Tokyo
Lieutenant-Colonel Seiichi Niizuma	Actively prevented information from becoming available to pre-war crime trial investigators	Worked at the Tokyo Research Institute of the Japan Self-Defense Force
Lieutenant-Colonel Dr. Ryōichi Naitō	Attempted to obtain yellow fever virus samples from the US before the war, duplicitously worked as an interpreter for a US war-crimes investigator immediately after the war	Worked as a private surgeon, founded the Japan Blood Bank, co-founded the Green Cross Corporation with Masaji Kitano & Hideo Futaki, member of the NYAS, Japanese Science Society award, Order of the Rising Sun
Lieutenant-General Masaji Kitano	Second in command	Co-founded Green Cross with Naitō & Futaki, formed a vaccine-producing company with Tamiya which went bankrupt, chief of the Tokyo branch of the Japan Blood Bank under Naitō
Lieutenant-Colonel Dr. Naitō Ikeda	Experiments on humans with hemorrhagic fever and tetanus	Ran a blood disease clinic in Osaka, published some of the details of his Unit 731 work in a scientific journal
Dr. Shirō Kasahara	Conducted experiments on humans of Songo (hemorrhagic) fever	Emeritus vice-president of the Kitasato hospital and Research Unit
Tadashi Yamashita	Photographer	Radiographer
Masakuni Kurumizawa	Assistant technician at vivisections	Farmer
Amitani Shogo	Tokyo University Laboratory for Communicable Diseases	Remained at this lab after the war, received the Asahi Prize for outstanding scientific performance
Ando Koji	Head of Dalian Laboratory	Professor of the Tokyo University Laboratory for Communicable Diseases, Head of the Central Laboratory for Experimental Animals
Kasuga Tadayoshi	Dalian Laboratory	Kitasato Research Laboratory, Ministry of Education Pertussis Research Team
Kimura Yasushi	Professor at Kyoto University	Assistant head of the Japan Medical Association, President of the Nagoya City University of Medicine
Kobayashi Rokuzo	Professor at Keio University	Director, First Division, National Institute of Health
Miyagawa Yoneji	Head of the Tokyo University Laboratory for Communicable Diseases	Toshiba Biophysics and Biochemistry Research Laboratory
Murata Yoshisuke	Unit 1644	JNIH
Ogata Tomio	Assistant professor at Tokyo University Laboratory for Communicable Diseases	Professor, Faculty of Medicine, Tokyo University
Okamoto Kozo	Pathology research team	Dean of the Faculty of Medicine at Kyoto University and Kinki University
Sonoguchi Tadao	Biological warfare development	Vice Principal, School of Hygiene at Japan Self-Defense Forces
Tanaka Hideo	Plague-carrying fleas team	Dean, Faculty of Medicine, Osaka City University
Toda Shozo	Professor, Kyoto University	Member of the Special Committee for Antarctic Research, President of Kanazawa University
Yanagizawa Ken	Tuberculosis research team	Head of the JNIH

Japanese exhibition

During 1993-1994, an exhibition concerning the activities of Unit 731 toured 61 locations in Japan. It included both written and in-person testimony from surviving Unit 731 members. A large part of the testimony was translated and published by Gold. The testimony largely corroborated previously published evidence.

Lessons unlearned

In 1969 US President Richard Nixon unilaterally terminated US biological weapons research, which led to the 1972 Biological Weapons Convention. The many signatories include the US, Russia (as the legal heir to the Soviet Union's treaty obligations) and Japan, but not China. China, as of 2024 is believed to have abided by the treaty even though it is not a signatory. Colonel Guo Ji-wei of the Chinese People’s Liberation Army (PLA) and past or former members of the PLA have discussed their use both in the context of supposed humaneness and the possibility of ethnic targeting. Russia meanwhile expanded its Cold War-era biological weapons research facility in 2024.

Gallery

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  Sketch of prison cells with octagonal pressure chamber for carrying out human experiments

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  Germ warfare experiment on a prisoner

See also

• Rape of Nanjing
• Comfort women
• Nazi human experimentation
• Weapons of mass destruction