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Unit 731

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A view to kill
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.[1] 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).[1] General Shirō IshiiWikipedia (石井 四郎) was the mastermind, creator and leader of the unit.[1]

The Unit 731 annual budget was larger than that of any Japanese university,[1] and was reportedly as large as the total tax revenue of Manchoukuo.[2]

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.[2] An estimated 3,000 prisoners were killed at Pingfang during the experiments, which left no prisoner alive.[3] There were survivors at the Mukden camp, but attrition was very high.[1]

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) campaignWikipedia, "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.[4][1][notes 1]

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.[1] 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.[2][5]


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.[6]

Japanese activity in the area of biological warfare was strongly suspected by the US as early as 1939,[1] 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).[4]

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.[1] 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.[1]

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.[1] 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.[1] 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.[1] Among the enormous amounts of documents presented at the Tokyo War Crimes Trials, only brief — and perhaps accidental — mention was given to biological weapons.[1]

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.[notes 2][1][5]

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.[2] Not all of the prisoners were necessarily affiliated with Unit 731, but they all would have been captured in northern China.

The unpunished[edit]

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).[1] 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.[1] The Khabarovsk trial had been essentially dismissed by the US as a show trial by the Soviets,[1] though it has now been established that the confessions and evidence reported from the trial were essentially completely accurate.[1][5]

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 KitanoWikipedia founded a multinational company, the Green Cross CorporationWikipedia, 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.[1][7]

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.[8] The list of 3,607 members includes "52 surgeons, 49 engineers, 38 nurses and 1,117 combat medics".[8]

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[1] and Gold.[2] 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.[9] 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 TakedaWikipedia (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 SuzukiWikipedia 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[10]
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[edit]

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.[2] The testimony largely corroborated previously published evidence.


See also[edit]


  1. In addition to the 1942 use of biological weapons in Chekiang, Dr. P. Z. King documented the following uses of biological weapons in China by the Japanese Army. In all cases, a Japanese airplane(s) dropped suspicious material (grain, fleas, granules, cloth) into areas where plague was not endemic; the material was clinically identified to contain Yersinia pestis, the plague bacteria.
    • Chuhsien, Chekiang Province, October 4, 1940: bubonic plague, 21 deaths
    • Ningpo (宁波市), Chekiang Province, October 29, 1940: bubonic plague, 99 victims
    • Kinhwa (金东区), November 28, 1940: Japanese planes dropped granules containing Y. pestis, but no plague infections reported
    • Changteh (常德会战), Hunan Province, November 4, 1941: plague, 6 cases of plague
  2. The convicted members of Unit 731 were (years of prison sentence in parentheses):
    1. General Otozō YamadaWikipedia (a.k.a., Otozoo Yamada) (山田 乙三), commander-in-chief of the Kwantung Army (25)
    2. Lieutenant General Ryuiji Kajitsuka, chief of Medical Administration in the Kwantung Army (25)
    3. Major General Kiyoshi Kawashima who was in charge of the experimental division (25)
    4. Lieutenant General Takaatsu Takahashi, who was head of the Veterinary Division (25)
    5. Major Tomio Karasawa who was in charge of a section that produced germs on large scale (25)
    6. Lieutenant Colonel Toshihide Nishi, who was responsible for breeding fleas, rats, mice, and guinea pigs (20)
    7. Major Masao Onoue bred laboratory animals and trained laboratory assistants (12)
    8. Major General Shunji SatoWikipedia was chief of Unit 8604 and Unit 1644 (20)
    9. Lieutenant Zensaku Hirazakura produced bacteria and poisons while in Unit 100 (10)
    10. Senior Sergeant Kazuo Mitomo manufactured anthrax, glanders cattle plague and sheep plague (15)
    11. Corporal Norimtsu Kikuchi attempted to produce a medium for growing typhoid and other bacteria (2)
    12. Private Yuji Kurushima was a laboratory orderly who dissected fleas, caught rats and put bacteria in test tubes, and was involved in biological warfare against China (3)


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 Unit 731: Japan's Secret Biological Warfare in World War II by Peter Williams & David Wallace (1989). Free Press. ISBN 0029353017.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 Gold, Hal. Unit 731 Testimony, Charles E Tuttle Co., 1996. ISBN 4-900737-39-9.
  3. Unit 731: Japan's Biological Warfare Project]
  4. 4.0 4.1 China Handbook 1937-1938: A Comprehensive Survey of Major Developments in China in Six Years of War, edited by Hollington K. Tong (July 1943) Chungking, China: The Chinese Ministry of Information.
  5. 5.0 5.1 5.2 Materials on the Trial of Former Servicemen of the Japanese Army Charged with Manufacturing and Employing Bacteriological Weapons. Foreign Languages Publishing House, 1950, 535 pp.
  6. Doctors of Depravity by Christopher Hudson (Last updated at 23:50 02 March 2007) Daily Mail.
  7. Japan's sins of the past: The memories of Japanese biological attacks on China in the 1940s are still fresh. Many Chinese want an apology by Justin McCurry (Thursday 28 October 2004 11.21 EDT) The Guardian.
  8. 8.0 8.1 Names of 3,607 members of Imperial Japanese Army’s notorious Unit 731 released by national archives (Apr 16, 2018) The Japan Times.
  9. An ethical blank cheque: British and US mythology about the second world war ignores our own crimes and legitimises Anglo-American warmaking by Richard Drayton (Monday 9 May 2005 19.37 EDT) The Guardian.
  10. Infection experiments with the flea and lice of epidemic hemorrhagic fever, Japan Infectious Diseases Society Journal, August 20, 1968, vol. 42, no. 5.