The Unit 731 complex. Two prisons are hidden in the center of the main building.
|Location||Pingfang, Harbin, Heilungkiang, Manchukuo|
|Deaths||Estimated 200,000 or 300,000–400,000 or higher from biological warfare|
Over 3,000 from inside experiments (not including branches, 1940–1945 only):20
At least 10,000 prisoners died
|Perpetrators||Surgeon General Shirō Ishii|
Lt. General Masaji Kitano
Epidemic Prevention and Water Purification Department
|Weapons of mass destruction|
Unit 731 (Japanese: 731部隊, Hepburn: Nana-san-ichi Butai), short for Manshu Detachment 731 and also known as Kamo Detachment,:198 Ishii Unit, was a covert biological and chemical warfare research and development unit of the Imperial Japanese Army that undertook lethal human experimentation during the Second Sino-Japanese War (1937–1945) of World War II. It was responsible for some of the most notorious war crimes carried out by Imperial Japan. Unit 731 was based at the Pingfang district of Harbin, the largest gas chamber in the Japanese puppet state of Manchukuo (now Northeast China), and had active branch offices throughout China and Southeast Asia.
It was officially known as the Epidemic Prevention and Water Purification Department of the Kwantung Army (関東軍防疫給水部本部, Kantōgun Bōeki Kyūsuibu Honbu). Originally set up under the Kenpeitai military police of the Empire of Japan, Unit 731 was taken over and commanded until the end of the war by General Shirō Ishii, a combat medic officer in the Kwantung Army. The facility itself was built in 1935 as a replacement for the Zhongma Fortress, and to expand the capabilities for Ishii and his team. The program received generous support from the Japanese government up to the end of the war in 1945. Unit 731 and the other units of the Epidemic Prevention and Water Purification Department were biological weapon production, testing, deployment and storage facilities. They routinely conducted tests on human beings (who were referred to internally as "logs"). Additionally, the biological weapons were tested in the field on cities and towns in China. Estimates of those killed by Unit 731 and its related programs range up to half a million people.
The researchers involved in Unit 731 were secretly given immunity by the United States in exchange for the data they gathered through human experimentation. Other researchers that the Soviet forces managed to arrest first were tried at the Khabarovsk War Crime Trials in 1949. The Americans did not try the researchers so that the information and experience gained in bio-weapons could be co-opted into their biological warfare program, much as they had done with German researchers in Operation Paperclip. On 6 May 1947, Douglas MacArthur, as Supreme Commander of the Allied Forces, wrote to Washington that "additional data, possibly some statements from Ishii, can probably be obtained by informing Japanese involved that information will be retained in intelligence channels and will not be employed as war crimes evidence". Victim accounts were then largely ignored or dismissed in the West as communist propaganda.
In 1932, Surgeon General Shirō Ishii (石井四郎, Ishii Shirō), chief medical officer of the Imperial Japanese Army and protégé of Army Minister Sadao Araki was placed in command of the Army Epidemic Prevention Research Laboratory (AEPRL). Ishii organized a secret research group, the "Tōgō Unit", for chemical and biological experimentation in Manchuria. Ishii had proposed the creation of a Japanese biological and chemical research unit in 1930, after a two-year study trip abroad, on the grounds that Western powers were developing their own programs.
One of Ishii's main supporters inside the army was Colonel Chikahiko Koizumi, who later became Japan's Health Minister from 1941 to 1945. Koizumi had joined a secret poison gas research committee in 1915, during World War I, when he and other Imperial Japanese Army officers were impressed by the successful German use of chlorine gas at the Second Battle of Ypres, in which the Allies suffered 5,000 deaths and 15,000 wounded as a result of the chemical attack.
Unit Tōgō was implemented in the Zhongma Fortress, a prison/experimentation camp in Beiyinhe, a village 100 km (62 mi) south of Harbin on the South Manchuria Railway. Prisoners were generally well fed on the usual diet of rice or wheat, meat, fish, and occasionally even alcohol, with the intent of having prisoners in their normal state of health at the beginning of experiments. Over several days, prisoners were eventually drained of blood and deprived of nutrients and water. Their deteriorating health was recorded. Some were also vivisected, while unconscious, if they developed a fever of 104 F. Others were deliberately infected with plague bacteria and other microbes.
In the autumn of 1934, a prison break, which jeopardized the facility's secrecy along with a later explosion (believed to be sabotage) in 1935 led Ishii to shut down Zhongma Fortress. He then received authorization to move to Pingfang, approximately 24 km (15 mi) south of Harbin, to set up a new, much larger facility.
In 1936, Emperor Hirohito authorized by decree the expansion of this unit and its integration into the Kwantung Army as the Epidemic Prevention Department. It was divided at that time into the "Ishii Unit" and "Wakamatsu Unit" with a base in Hsinking. From August 1940, the units were known collectively as the "Epidemic Prevention and Water Purification Department of the Kwantung Army (関東軍防疫給水部本部)" or "Unit 731" (満州第731部隊) for short.
In addition to the establishment of Unit 731, the decree also called for the establishment of an additional biological warfare development unit called the Kwantung Army Military Horse Epidemic Prevention Workshop (later referred to as Manchuria Unit 100) and a chemical warfare development unit called the Kwantung Army Technical Testing Department (later referred to as Manchuria Unit 516). After the Japanese invasion of China in 1937, sister chemical and biological warfare units were founded in major Chinese cities, and were referred to as Epidemic Prevention and Water Supply Units. Detachments included Unit 1855 in Beijing, Unit Ei 1644 in Nanjing, Unit 8604 in Guangzhou and later, Unit 9420 in Singapore. All of these units comprised Ishii's network, and at its height in 1939, was composed of more than 10,000 personnel. Medical doctors and professors from Japan were attracted to join Unit 731 by the rare opportunity to conduct human experimentation and strong financial support from the Army.
A special project code-named Maruta used human beings for experiments. Test subjects were gathered from the surrounding population and were sometimes referred to euphemistically as "logs" (丸太, maruta), used in such contexts as "How many logs fell?". This term originated as a joke on the part of the staff because the official cover story for the facility given to the local authorities was that it was a lumber mill. However, in an account by a man who worked as a junior uniformed civilian employee of the Imperial Japanese Army in Unit 731, the project was internally called "Holzklotz", which is a German word for log. In a further parallel, the corpses of "sacrificed" subjects were disposed of by incineration. Researchers in Unit 731 also published some of their results in peer-reviewed journals, writing as though the research had been conducted on non-human primates called "Manchurian monkeys" or "long-tailed monkeys".
The test subjects were selected to give a wide cross-section of the population and included common criminals, captured bandits, anti-Japanese partisans, political prisoners, the homeless and mentally handicapped, and also people rounded up by the Kempeitai military police for alleged "suspicious activities". They included infants, men, the elderly, and pregnant women. The members of the unit, approximately 300 researchers, included doctors and bacteriologists. Many had been desensitized to performing cruel experiments from experience in animal research.
Prisoners were injected with diseases, disguised as vaccinations, to study their effects. To study the effects of untreated venereal diseases, male and female prisoners were deliberately infected with syphilis and gonorrhoea, then studied. Prisoners were also repeatedly subject to rape by guards.
Thousands of men, women, children and infants interned at prisoner of war camps were subjected to vivisection, often without anesthesia and usually ending with the death of the victim. Vivisections were performed on prisoners after infecting them with various diseases. Researchers performed invasive surgery on prisoners, removing organs to study the effects of disease on the human body.
Prisoners had limbs amputated in order to study blood loss. Those limbs that were removed were sometimes re-attached to the opposite sides of the body. Some prisoners had their stomachs surgically removed and the esophagus reattached to the intestines. Parts of organs, such as the brain, lungs, and liver, were removed from some prisoners. Imperial Japanese Army surgeon Ken Yuasa suggests that the practice of vivisection on human subjects was widespread even outside Unit 731, estimating that at least 1,000 Japanese personnel were involved in the practice in mainland China.
Unit 731 and its affiliated units (Unit 1644 and Unit 100 among others) were involved in research, development and experimental deployment of epidemic-creating biowarfare weapons in assaults against the Chinese populace (both military and civilian) throughout World War II. Plague-infected fleas, bred in the laboratories of Unit 731 and Unit 1644, were spread by low-flying airplanes upon Chinese cities, including coastal Ningbo and Changde, Hunan Province, in 1940 and 1941. This military aerial spraying killed tens of thousands of people with bubonic plague epidemics. An expedition to Nanking involved spreading typhoid and paratyphoid germs into the wells, marshes, and houses of the city, as well as infusing them into snacks to be distributed among the locals. Epidemics broke out shortly after, to the elation of many researchers, where it was concluded that paratyphoid fever was "the most effective" of the pathogens.
At least 12 large-scale field trials of biological weapons were performed, and at least 11 Chinese cities were attacked with biological agents. An attack on Changda in 1941 reportedly led to approximately 10,000 biological casualties and 1,700 deaths among ill-prepared Japanese troops, with most cases due to cholera. Japanese researchers performed tests on prisoners with bubonic plague, cholera, smallpox, botulism, and other diseases. This research led to the development of the defoliation bacilli bomb and the flea bomb used to spread bubonic plague. Some of these bombs were designed with porcelain shells, an idea proposed by Ishii in 1938.
These bombs enabled Japanese soldiers to launch biological attacks, infecting agriculture, reservoirs, wells, as well as other areas with anthrax, plague-carrier fleas, typhoid, dysentery, cholera or other deadly pathogens. During biological bomb experiments, researchers dressed in protective suits would examine the dying victims. Infected food supplies and clothing were dropped by airplane into areas of China not occupied by Japanese forces. In addition, poisoned food and candies were given to unsuspecting victims.
During the final months of World War II, Japan planned to use plague as a biological weapon against San Diego, California. The plan was scheduled to launch on September 22, 1945, but Japan surrendered five weeks earlier. Plague fleas, infected clothing and infected supplies encased in bombs were dropped on various targets. The resulting cholera, anthrax, and plague were estimated to have killed at least 400,000 Chinese civilians. Tularemia was also tested on Chinese civilians.
Due to pressure from numerous accounts of the bio-warfare attacks, Chiang Kai-shek sent a delegation of army and foreign medical personnel in November 1941 to document evidence and treat the afflicted. A report on the Japanese use of plague-infested fleas on Changde was made widely available the following year, but was not addressed by the Allied Powers until Franklin D. Roosevelt issued a public warning in 1943 condemning the attacks.
Human targets were used to test grenades positioned at various distances and in various positions. Flamethrowers were tested on humans. Humans were also tied to stakes and used as targets to test pathogen-releasing bombs, chemical weapons, and explosive bombs as well as bayonets and knives.
In other tests, subjects were deprived of food and water to determine the length of time until death; placed into low-pressure chambers until their eyes popped from the sockets; experimented upon to determine the relationship between temperature, burns, and human survival; electrocuted; placed into centrifuges and spun until death; injected with animal blood; exposed to lethal doses of x-rays; subjected to various chemical weapons inside gas chambers; injected with sea water; and burned or buried alive.
Army Engineer Hisato Yoshimura conducted experiments by taking captives outside, dipping various appendages into water of varying temperatures, and allowing the limb to freeze. Once frozen, Yoshimura would strike their affected limbs with a short stick, "emitting a sound resembling that which a board gives when it is struck'". Ice was then chipped away, with the affected area being subjected to various treatments such as being doused in water, exposed to the heat of fire etc.
Unit members orchestrated forced sex acts between infected and non-infected prisoners to transmit the disease, as the testimony of a prison guard on the subject of devising a method for transmission of syphilis between patients shows:
"Infection of venereal disease by injection was abandoned, and the researchers started forcing the prisoners into sexual acts with each other. Four or five unit members, dressed in white laboratory clothing completely covering the body with only eyes and mouth visible, rest covered, handled the tests. A male and female, one infected with syphilis, would be brought together in a cell and forced into sex with each other. It was made clear that anyone resisting would be shot."
After victims were infected, they were vivisected at different stages of infection, so that internal and external organs could be observed as the disease progressed. Testimony from multiple guards blames the female victims as being hosts of the diseases, even as they were forcibly infected. Genitals of female prisoners that were infected with syphilis were called "jam filled buns" by guards.
Some children grew up inside the walls of Unit 731, infected with syphilis. A Youth Corps member deployed to train at Unit 731 recalled viewing a batch of subjects that would undergo syphilis testing: "one was a Chinese woman holding an infant, one was a White Russian woman with a daughter of four or five years of age, and the last was a White Russian woman with a boy of about six or seven." The children of these women were tested in ways similar to their parents, with specific emphasis on determining how longer infection periods affected the effectiveness of treatments.
Female prisoners were forced to become pregnant for use in experiments. The hypothetical possibility of vertical transmission (from mother to child) of diseases, particularly syphilis, was the stated reason for the torture. Fetal survival and damage to mother's reproductive organs were objects of interest. Though "a large number of babies were born in captivity", there have been no accounts of any survivors of Unit 731, children included. It is suspected that the children of female prisoners were killed after birth or aborted.
While male prisoners were often used in single studies, so that the results of the experimentation on them would not be clouded by other variables, women were sometimes used in bacteriological or physiological experiments, sex experiments, and as the victims of sex crimes. The testimony of a unit member that served as guard graphically demonstrated this reality:
"One of the former researchers I located told me that one day he had a human experiment scheduled, but there was still time to kill. So he and another unit member took the keys to the cells and opened one that housed a Chinese woman. One of the unit members raped her; the other member took the keys and opened another cell. There was a Chinese woman in there who had been used in a frostbite experiment. She had several fingers missing and her bones were black, with gangrene set in. He was about to rape her anyway, then he saw that her sex organ was festering, with pus oozing to the surface. He gave up the idea, left and locked the door, then later went on to his experimental work."
In 2002, Changde, China, site of the plague flea bombing, held an "International Symposium on the Crimes of Bacteriological Warfare" which estimated that the number of people killed by the Imperial Japanese Army germ warfare and other human experiments was around 580,000. The American historian Sheldon H. Harris states that over 200,000 died. In addition to Chinese casualties, 1,700 Japanese troops in Zhejiang during Zhejiang-Jiangxi campaign were killed by their own biological weapons while attempting to unleash the biological agent, indicating serious issues with distribution.
At least 3,000 men, women, and children:117—from which at least 600 every year were provided by the Kempeitai were subjected to experimentation conducted by Unit 731 at the camp based in Pingfang alone, which does not include victims from other medical experimentation sites, such as Unit 100.
According to A. S. Wells, the majority of victims were Chinese with a lesser percentage being Russian, Mongolian, and Korean. They may also have included a small number of European, American, Indian, Australian and New Zealander prisoners of war. Sheldon H. Harris documented that the victims were generally political dissidents, communist sympathizers, ordinary criminals, impoverished civilians, and the mentally handicapped. Author Seiichi Morimura estimates that almost 70% of the victims who died in the Pingfang camp were Chinese (including both military and civilian), while close to 30% of the victims were Russian.
Imprisoned as a POW at the Mukden camp (housing American, British, Australian and New Zealand soldiers) Robert Peaty (1903–1989), a Major in the Royal Army Ordnance Corps, was the senior ranking allied officer. During his captivity, he kept a secret diary. He was interviewed by the Imperial War Museum in 1981, and the audio recording tape reels are in the IWM's archives. Peaty recounts: "I was reminded of Dante’s Inferno – abandon hope all ye who enter here ...." His diary recorded the regular injections of infectious diseases that were disguised as preventative vaccinations. His entry for January 30, 1943 notes: "Everyone received a 5 cc Typhoid-paratyphoid A inoculation." The February 23, 1943 entry read: "Funeral service for 142 dead. 186 have died in 5 days, all Americans."
In April 2018, the National Archives of Japan for the first time disclosed a nearly complete list of 3,607 people who worked for Unit 731 to Katsuo Nishiyama of the Shiga University of Medical Science, who says that he intends to publish the list online.
Previously disclosed members include:
There were also twelve members who were formally tried and sentenced in the Khabarovsk War Crime Trials.
|Name||Military position||Unit position:5||Unit||Sentenced years in labor camp:534–535|
|Kiyoshi Shimizu||Lieutenant colonel||Chief of General Division, 1939–1941, Head of Production Division, 1941–1945:131||731||25|
|Otozō Yamada||General||Direct controller, 1944–1945:232||731, 100||25|
|Ryuji Kajitsuka||Lieutenant general of the Medical Service||Chief of the Medical Administration:131||731||25|
|Takaatsu Takahashi||Lieutenant general of the Veterinary Service||Chief of the Veterinary Service||731||25|
|Tomio Karasawa||Major of the Medical Service||Chief of a section||731||20|
|Toshihide Nishi||Lieutenant colonel of the Medical Service||Chief of a division||731||18|
|Masao Onoue||Major of the Medical Service||Chief of a branch||731||12|
|Kazuo Mitomo||Senior sergeant||Member||731||15|
|Norimitsu Kikuchi||Corporal||Probationer medical orderly||Branch 643||2|
|Yuji Kurushima||[none]||Laboratory orderly||Branch 162||3|
|Shunji Sato||Major general of the Medical Service||Chief of the Medical Service:192||731, 1644||20|
Unit 731 was divided into eight divisions:
Unit 731 had other units underneath it in the chain of command; there were several other units under the auspice of Japan's biological weapons programs. Most or all Units had branch offices, which were also often referred to as "Units". The term Unit 731 can refer to the Harbin complex itself, or it can refer to the organization and its branches, sub-Units and their branches.
The Unit 731 complex covered six square kilometres (2.3 square miles) and consisted of more than 150 buildings. The design of the facilities made them hard to destroy by bombing. The complex contained various factories. It had around 4,500 containers to be used to raise fleas, six cauldrons to produce various chemicals, and around 1,800 containers to produce biological agents. Approximately 30 kilograms (66 pounds) of bubonic plague bacteria could be produced in a few days.
A medical school and research facility belonging to Unit 731 operated in the Shinjuku District of Tokyo during World War II. In 2006, Toyo Ishii—a nurse who worked at the school during the war—revealed that she had helped bury bodies and pieces of bodies on the school's grounds shortly after Japan's surrender in 1945. In response, in February 2011 the Ministry of Health began to excavate the site.
China requested DNA samples from any human remains discovered at the site. The Japanese government—which until then had never officially acknowledged the atrocities committed by Unit 731—rejected the request.
Operations and experiments continued until the end of the war. Ishii had wanted to use biological weapons in the Pacific War since May 1944, but his attempts were repeatedly snubbed.
With the coming of the Red Army in August 1945, the unit had to abandon their work in haste. Ministries in Tokyo ordered the destruction of all incriminating materials, including those in Pingfang. Potential witnesses, such as the 300 remaining prisoners were either gassed or fed poison while the 600 Chinese and Manchurian laborers were shot. Ishii ordered every member of the group to disappear and "take the secret to the grave". Potassium cyanide vials were issued for use in the event that the remaining personnel were captured.
Skeleton crews of Ishii's Japanese troops blew up the compound in the final days of the war to destroy evidence of their activities, but many were sturdy enough to remain somewhat intact.
Among the individuals in Japan after its 1945 surrender was Lieutenant Colonel Murray Sanders, who arrived in Yokohama via the American ship Sturgess in September 1945. Sanders was a highly regarded microbiologist and a member of America's military center for biological weapons. Sanders' duty was to investigate Japanese biological warfare activity. At the time of his arrival in Japan he had no knowledge of what Unit 731 was. Until Sanders finally threatened the Japanese with bringing the Soviets into the picture, little information about biological warfare was being shared with the Americans. The Japanese wanted to avoid prosecution under the Soviet legal system, so the next morning after he made his threat, Sanders received a manuscript describing Japan's involvement in biological warfare. Sanders took this information to General Douglas MacArthur, who was the Supreme Commander of the Allied Powers responsible for rebuilding Japan during the Allied occupations. MacArthur struck a deal with Japanese informants: He secretly granted immunity to the physicians of Unit 731, including their leader, in exchange for providing America, but not the other wartime allies, with their research on biological warfare and data from human experimentation. American occupation authorities monitored the activities of former unit members, including reading and censoring their mail. The Americans believed that the research data was valuable, and did not want other nations, particularly the Soviet Union, to acquire data on biological weapons.
The Tokyo War Crimes Tribunal heard only one reference to Japanese experiments with "poisonous serums" on Chinese civilians. This took place in August 1946 and was instigated by David Sutton, assistant to the Chinese prosecutor. The Japanese defense counsel argued that the claim was vague and uncorroborated and it was dismissed by the tribunal president, Sir William Webb, for lack of evidence. The subject was not pursued further by Sutton, who was probably unaware of Unit 731's activities. His reference to it at the trial is believed to have been accidental.
Although publicly silent on the issue at the Tokyo Trials, the Soviet Union pursued the case and prosecuted twelve top military leaders and scientists from Unit 731 and its affiliated biological-war prisons Unit 1644 in Nanjing, and Unit 100 in Changchun, in the Khabarovsk War Crime Trials. Included among those prosecuted for war crimes, including germ warfare, was General Otozō Yamada, the commander-in-chief of the million-man Kwantung Army occupying Manchuria.
The trial of those captured Japanese perpetrators was held in Khabarovsk in December 1949. A lengthy partial transcript of the trial proceedings was published in different languages the following year by a Moscow foreign languages press, including an English-language edition. The lead prosecuting attorney at the Khabarovsk trial was Lev Smirnov, who had been one of the top Soviet prosecutors at the Nuremberg Trials. The Japanese doctors and army commanders who had perpetrated the Unit 731 experiments received sentences from the Khabarovsk court ranging from two to 25 years in a Siberian labor camp. The United States refused to acknowledge the trials, branding them communist propaganda. The sentences doled out to the Japanese perpetrators were unusually lenient by Soviet standards, and all but one of the defendants returned to Japan by the 1950s (with the remaining prisoner committing suicide inside his cell). In addition to the accusations of propaganda, the US also asserted that the trials were to only serve as a distraction from the Soviet treatment of several hundred thousand Japanese prisoners of war; meanwhile, the USSR asserted that the US had given the Japanese diplomatic leniency in exchange for information regarding their human experimentation. The accusations of both the US and the USSR were true, and it is believed that the Japanese had also given information to the Soviets regarding their biological experimentation for judicial leniency. This was evidenced by the Soviet Union building a biological weapons facility in Sverdlovsk using documentation captured from Unit 731 in Manchuria.
As above, under the American occupation the members of Unit 731 and other experimental units were allowed to go free. One graduate of Unit 1644, Masami Kitaoka, continued to do experiments on unwilling Japanese subjects from 1947 to 1956 while working for Japan's National Institute of Health Sciences. He infected prisoners with rickettsia and mental health patients with typhus.
Shiro Ishii, as the chief of the unit, was granted war crime immunity from the US occupation authorities, because of his provision of human experimentation research materials to the US. From 1948 to 1958, less than 5% of the documents were transferred onto microfilm and stored in the National Archives of the United States, before being shipped back to Japan.
Japanese discussions of Unit 731's activity began in the 1950s, after the end of the American occupation of Japan. In 1952, human experiments carried out in Nagoya City Pediatric Hospital, which resulted in one death, were publicly tied to former members of Unit 731. Later in that decade, journalists suspected that the murders attributed by the government to Sadamichi Hirasawa were actually carried out by members of Unit 731. In 1958, Japanese author Shūsaku Endō published the book The Sea and Poison about human experimentation, which is thought to have been based on a real incident.
The author Seiichi Morimura published The Devil's Gluttony (悪魔の飽食) in 1981, followed by The Devil's Gluttony: A Sequel in 1983. These books purported to reveal the "true" operations of Unit 731, but falsely attributed unrelated photos to the Unit, which raised questions about their accuracy.
Also in 1981 appeared the first direct testimony of human vivisection in China, by Ken Yuasa. Since then many more in-depth testimonies have appeared in Japanese. The 2001 documentary Japanese Devils was composed largely of interviews with 14 members of Unit 731 who had been taken as prisoners by China and later released.
There was consensus among US researchers in the postwar period that the human experimentation data gained was of little value to the development of American biological weapons and medicine. Postwar reports have generally regarded the data as "crude and ineffective", with one expert even deeming it "amateurish". Harris speculates that the reason US scientists generally wanted to acquire it was due to the concept of forbidden fruit, believing that lawful and ethical prohibitions could affect the outcomes of their research.
Unit 731 presents a special problem, since unlike Nazi human experimentation, which the United States publicly condemned, the activities of Unit 731 are known to the general public only from the testimonies of willing former unit members, and testimony cannot be employed to determine indemnity in this way.
Japanese history textbooks usually contain references to Unit 731, but do not go into detail about allegations, in accordance with this principle. Saburō Ienaga's New History of Japan included a detailed description, based on officers' testimony. The Ministry for Education attempted to remove this passage from his textbook before it was taught in public schools, on the basis that the testimony was insufficient. The Supreme Court of Japan ruled in 1997 that the testimony was indeed sufficient and that requiring it to be removed was an illegal violation of freedom of speech.
In 1997, the international lawyer Kōnen Tsuchiya filed a class action suit against the Japanese government, demanding reparations for the actions of Unit 731, using evidence filed by Professor Makoto Ueda of Rikkyo University. All Japanese court levels found that the suit was baseless. No findings of fact were made about the existence of human experimentation, but the decision of the court was that reparations are determined by international treaties and not by national court cases.
In August 2002, the Tokyo district court ruled for the first time that Japan had engaged in biological warfare. Presiding judge Koji Iwata ruled that Unit 731, on the orders of the Imperial Japanese Army headquarters, used bacteriological weapons on Chinese civilians between 1940 and 1942, spreading diseases including plague and typhoid in the cities of Quzhou, Ningbo, and Changde. However, he rejected the victims' claims for compensation on the grounds that they had already been settled by international peace treaties.
In October 2003, a member of the House of Representatives of Japan filed an inquiry. Prime Minister Junichiro Koizumi responded that the Japanese government did not then possess any records related to Unit 731, but the government recognized the gravity of the matter and would publicize any records that were located in the future. In April 2018, the National Archives of Japan released the names of 3,607 members of Unit 731, in response to a request by Professor Katsuo Nishiyama of the Shiga University of Medical Science.
After WWII, the Office of Special Investigations created a watchlist of suspected Axis collaborators and persecutors that are banned from entering the United States. While they have added over 60,000 names to the watchlist, they have only been able to identify under 100 Japanese participants. In a 1998 correspondence letter between the DOJ and Rabbi Abraham Cooper, Eli Rosenbaum, director of OSI, stated that this was due to two factors. (1) While most documents captured by the US in Europe were microfilmed before being returned to their respective governments, the Department of Defense decided to not microfilm its vast collection of documents before returning them back to the Japanese government. (2) The Japanese government has also failed to grant the OSI meaningful access to these and related records after the war, while European countries, on the other hand, have been largely cooperative, the cumulative effect of which is that information pertaining to identifying these individuals is, in effect, impossible to recover.
There have been several films about the atrocities of Unit 731.