Unit 731

The Empire of Japan initiated its biological weapons program during the 1930s, due to the prohibition of biological weapons in interstate conflicts by the Geneva Protocol of 1925. They reasoned that the ban implied their efficacy as weapons. Japan decided to build Unit 731 in Manchuria because the occupation not only gave the Japanese an advantage of separating the research station from their island but also gave them access to as many Chinese individuals as they wanted for use as test subjects. The research and experimentation rooms were constructed around the detention area, allowing researchers to conduct their daily work while monitoring the prisoners. Unit 731 was a clandestine division of the Japanese Kwantung Army based in Manchuria during World War II. Led by Lieutenant General Shirō Ishii, the organization dedicated to the advancement of biological weaponry within the imperial army was commonly referred to as the Ishii Network. The Ishii Network was headquartered at the Epidemic Prevention Research Laboratory, established in 1932 at the Japanese Army Military Medical School in Tokyo. Unit 731 was the first of several covert units established as offshoots of the research lab, serving as field stations and experimental sites to advance biological warfare techniques. These efforts culminated in the experimental deployment of biological weapons on Chinese cities, a direct breach of the 1925 Geneva Protocol prohibiting the use of biological and chemical weapons in warfare. Participants in these activities were aware of the violations and recognized the inhumanity of using human subjects in laboratory experiments, prompting the establishment of Unit 731 and other secret units. It was divided at that time into the "Ishii Unit" and the "Wakamatsu Unit", with a base in Xinjing. From August 1940 on, the units were known collectively as the "Epidemic Prevention and Water Purification Department of the Kwantung Army" or "Unit 731" for short. One of Ishii's main supporters inside the army was Colonel Chikahiko Koizumi, who later served as 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 6,000 deaths and 15,000 wounded as a result of the chemical attack. Zhongma Fortress Unit Tōgō was set into motion in the Zhongma Fortress, a prison and experimentation camp in Beiyinhe, a village south of Harbin on the South Manchuria Railway. The prisoners brought to Zhongma included common criminals, captured bandits, and anti-Japanese partisans, as well as political prisoners and people rounded up on false charges by the Kempeitai. Prisoners were generally well fed on a diet of rice or wheat, meat, fish, and occasionally even alcohol, in order to be in normal health at the beginning of experiments. Then, over several days, prisoners were eventually drained of blood and deprived of nutrients and water. Their deteriorating health was recorded. Some were also vivisected. Others were deliberately infected with plague bacteria and other microbes. A prison break in the autumn of 1934, which jeopardized the facility's secrecy, and an explosion in 1935, which was believed to be sabotage, led Ishii to shut down the Zhongma Fortress. He then received authorization to relocate to Pingfang, approximately south of Harbin, to establish a new, much larger facility. Other units In addition to the establishment of Unit 731, the decree also called for the creation 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, Malaya (present-day Malaysia), Indonesia, the Philippines, Papua New Guinea, Thailand, and Burma. All of these units comprised Ishii's network, which, at its height in 1939, oversaw over 10,000 personnel. Medical doctors and professors from Japan were enticed to join Unit 731 both by the rare opportunity to conduct human experimentation and the Army's strong financial backing. == Experiments ==

The military police and the Special Services Agency were responsible for locating victims to serve as test subjects for the unit, while a group of physicians was tasked with maintaining the health of the victims and dispatching them for experimentation. According to American historian Sheldon H. Harris: The Togo Unit employed gruesome tactics to secure specimens of select body organs. If Ishii or one of his co-workers wished to do research on the human brain, then they would order the guards to find them a useful sample. A prisoner would be taken from his cell. Guards would hold him while another guard would smash the victim's head open with an axe. His brain would be extracted off to the pathologist, and then to the crematorium for the usual disposal. Nakagawa Yonezo, professor emeritus at Osaka University, studied at Kyoto University during the war. While he was there, he watched footage of human experiments and executions from Unit 731. He later testified about the playfulness of the experimenters: Some of the experiments had nothing to do with advancing the capability of germ warfare, or of medicine. There is such a thing as professional curiosity: 'What would happen if we did such and such?' What medical purpose was served by performing and studying beheadings? None at all. That was just playing around. Professional people, too, like to play. 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 gonorrhea, then studied. A special project, codenamed Maruta, used human beings for experiments. Test subjects were gathered from the surrounding population and sometimes euphemistically referred to as , as in "How many logs fell?" This term originated as a staff joke because the official cover story for the facility, given to local authorities, was that it was a lumber mill. According to a junior uniformed civilian employee of the Imperial Japanese Army working in Unit 731, the project was internally called "Holzklotz", from the German word for log. The corpses of "sacrificed" subjects were disposed of by incineration. At the age of 14, on the encouragement of a former school teacher, Hideo Shimizu joined the fourth group of minors assigned to Unit 731. He recalled that he was brought to a specimen room where jars of various heights, with some reaching the height of an adult, were stored. In a video interview, former Unit 731 member Okawa Fukumatsu admitted to having vivisected a pregnant woman. 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. Limbs removed were sometimes reattached to the opposite side of the victims' bodies. Some prisoners had their stomachs surgically removed and their esophagus reattached to the intestines. Parts of organs, such as the brain, lungs, and liver, were removed from others. Yuasa said that when he performed vivisections on captives, they were "all for practice rather than for research", and that such practices were "routine" among Japanese doctors stationed in China during the war. Biological warfare s facility Unit 731 and its affiliated units (Unit 1644 and Unit 100, among others) were involved in research, development and experimental deployment of epidemic-creating biological weapons in assaults against the Chinese populace (both military and civilian) throughout World War II. The Library of Congress holds three declassified documents from Unit 731, each more than 100 pages long, translated from Japanese into English. These documents provided comprehensive clinical records about the daily progression of various pathogens within the bodies of helpless prisoners who were experimented on by Japanese doctors. Japanese soldiers provided testimony indicating that the research program had the capability to manufacture substantial quantities of biological agents on a monthly basis: 300 kg of plague, 500–700 kg of anthrax, 800–900 kg of typhoid, and 1,000 kg of cholera. Despite the significant production volumes, even small amounts of these bacteria could cause severe harm or death. Ishii determined that fleas were efficient carriers of the plague, leading Unit 731 to focus on breeding large numbers of fleas. To achieve this goal, Unit 731 had approximately 4500 flea incubators, each capable of producing at least 45 kg of fleas per cycle. The substantial quantities of plague bacteria and fleas generated, combined with the severe illness and death rates associated with plague infection, illustrate the formidable biological warfare production capabilities wielded by the Japanese. Japanese researchers had the necessary materials to apply the scientific method to conduct experiments involving inoculation and the creation of airborne bacterial bombs. 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- and plague-carrier fleas, typhoid, 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 candy were given to unsuspecting victims. 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 biowarfare 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-infected 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. In December 1944, the Japanese Navy explored the possibility of attacking cities in California with biological weapons, known as Operation PX or Operation Cherry Blossoms at Night. The plan for the attack involved Seiran aircraft launched by Sentoku submarine aircraft carriers upon the West Coast of the United States—specifically, the cities of San Diego, Los Angeles, and San Francisco. The planes would spread weaponized bubonic plague, cholera, typhus, dengue fever, and other pathogens in a biological terror attack upon the population. The submarine crews would infect themselves and run ashore in a suicide mission. Weapons testing Human targets were used to test grenades at various distances and positions. Flamethrowers were tested on people. Victims were also tied to stakes and used as targets to test pathogen-releasing bombs, chemical weapons, shrapnel bombs with varying amounts of fragments, and explosive bombs as well as bayonets and knives. Frostbite testing 's frostbite research data 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". Naoji Uezono, a member of Unit 731, described in a 1980s interview a grisly scene where Yoshimura had "two naked men put in an area 40–50 degrees below zero and researchers filmed the whole process until [the subjects] died. [The subjects] suffered such agony they were digging their nails into each other's flesh." Yoshimura's lack of remorse was evident in an article he wrote for the Japanese Journal of Physiology in 1950 in which he admitted to using 20 children and a three-day-old infant in experiments which exposed them to zero-degree-Celsius ice and salt water. Although this article drew criticism, Yoshimura denied any guilt when contacted by a reporter from the Mainichi Shimbun. Yoshimura developed a "resistance index of frostbite" based on the mean temperature 5 to 30 minutes after immersion in freezing water, the temperature of the first rise after immersion, and the time until the temperature first rises after immersion. In a number of separate experiments it was then determined how these parameters depend on the time of day a victim's body part was immersed in freezing water, the surrounding temperature and humidity during immersion, how the victim had been treated before the immersion ("after keeping awake for a night", "after hunger for 24 hours", "after hunger for 48 hours", "immediately after heavy meal", "immediately after hot meal", "immediately after muscular exercise", "immediately after cold bath", "immediately after hot bath"), what type of food the victim had been fed over the five days preceding the immersions with regard to dietary nutrient intake ("high protein (of animal nature)", "high protein (of vegetable nature)", "low protein intake", and "standard diet"), and salt intake (45 g NaCl per day, 15 g NaCl per day, no salt). This original data is seen in the attached figure. Syphilis 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 victims shows: 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. • Spinning in centrifuges until death; • Exposure to extreme heat and burns; • Injection with animal blood, including horse blood; • Injection with seawater; • Burning or live burial. Dehydration experiments aimed to measure total body water content and survival duration without water. Victims were often starved before testing. Staff documented their physical decline at regular intervals. Chemical and toxin exposure Victims were exposed to a wide range of toxic agents including: • Mustard gas; • Lewisite; • Cyanic acid gas; • White phosphorus; • Adamsite; • Phosgene. Unit 731 operated a facility dedicated to gas chamber experiments. Victims were placed in sealed chambers wearing either full uniform, partial gear, or no protection. A former army major and later professor emeritus recalled: Field testing Unit 731 conducted field trials of chemical weapons. A report from the Kamo Unit described yperite (mustard gas) experiments on 7–10 September 1940 involving 20 prisoners in various clothing conditions. Subjects were exposed to up to 4,800 artillery rounds. Symptoms were documented at multiple intervals. In one case, fluid from blisters was injected into other subjects, and blood and stool were analyzed. Five prisoners were forced to drink yperite–lewisite solutions. Blood and toxin research Unit 731 studied blood loss and incompatible blood transfusions. Former member Okawa Fukumatsu stated that some prisoners had 500 ml of blood withdrawn every two to three days. Experiments with incompatible blood types were conducted. Unit member Naeo Ikeda recorded: Prisoners were also exposed to biological toxins including tetrodotoxin (from pufferfish), heroin, Korean bindweed, bactal, and castor oil seeds (containing ricin). == Prisoners and victims ==

After Japan's defeat in World War II, the Japanese murdered every single prisoner in the unit. The remains were then buried in the Unit 731 grounds after being cremated. The following testimony explains how the captives were murdered: On August 11 and 12, after the end of the war, approximately 300 prisoners were disposed of. The prisoners were coerced into suicide by being given a piece of rope. One quarter of them hung themselves, and the remaining three quarters who would not consent to suicide were made to drink potassium cyanide and killed by injection. In the end all were taken care of. The prisoners were made to drink potassium cyanide by mixing it with water and putting it into bowls. The injections were most likely chloroform. Harris also said plague-infected animals were released near the end of the war, and caused plague outbreaks that killed at least 30,000 people in the Harbin area from 1946 to 1948. At least 3,000 men, women, and children—were subjected to Unit 731 experimentation conducted at the Pingfang camp alone, not including victims from other medical experimentation sites such as Unit 100. Although 3,000 internal victims is the widely accepted figure in the literature, former Unit member Okawa Fukumatsu claims that there were at least 10,000 victims of internal experiments at the Unit, he himself vivisecting thousands. A member of the Yokusan Sonendan paramilitary political youth branch, who worked for Unit 731, stated that not only were Chinese, Russians, and Koreans present, but also Americans, British, and French people. Sheldon H. Harris documented that the victims were generally political dissidents, communist sympathizers, ordinary criminals, impoverished civilians, and the mentally disabled. Author Seiichi Morimura estimates that almost 70 percent of the victims who died in the Pingfang camp were Chinese (both military and civilian), while close to 30 percent of the victims were Russian. represents the pressure chamber. No Unit 731 prisoners survived. Prisoners were usually received into Unit 731 at night in motor vehicles painted black with a ventilation hole but no windows. Once deemed healthy and fit for experimentation, prisoners lost their names and were given a three-digit number, which they retained until their death. Whenever prisoners died after the experiments they had been subjected to, a clerk of the 1st Division struck their numbers off an index card and took the deceased prisoner's manacles to be put on new arrivals to the prison. The prison cells had wooden floors and a squat toilet in each. There was space between the outer walls of the cells and the outer walls of the prison, enabling the guards to walk behind the cells. Each cell door had a small window in it. Chief of the Personnel Division of the Kwantung Army Headquarters Tamura Tadashi testified that, when he was shown the inner-prison, he looked into the cells and saw living people in chains, some moved around, others were lying on the bare floor and were in a very sick and helpless condition. The second attempt occurred in the summer of 1945. Corporal Kikuchi Norimitsu testified that he was told by another unit member that a prisoner "had shown violence and had struck the experimenter with a door handle" and then "jumped out of the cell and ran down the corridor, seized the keys and opened the iron doors and some of the cells. Some of the prisoners managed to jump out but these were only the bold ones. These bold ones were shot." Unfortunately for the prisoners of Unit 731, escape was an impossibility. Even if they had managed to escape the quadrangle (itself a heavily fortified building full of staff), they would have had to get over a brick wall surrounding the complex, and then across a dry moat filled with electrified wire running around the perimeter of the complex. Experiments on staff members Members of Unit 731 were not immune from being subjects of experiments. Yoshio Tamura, an assistant in the Special Team, recalled that Yoshio Sudō, an employee of the first division at Unit 731, became infected with bubonic plague as a result of its production. The Special Team was then ordered to vivisect Sudō. Tamura recalled: Additionally, Unit 731 Youth Corps member Yoshio Shinozuka testified that his friend, junior assistant Mitsuo Hirakawa, was vivisected as a result of being accidentally infected with plague. == Personnel and postwar accountability ==

Unit 731 included hundreds of military and civilian personnel who participated in wartime human experimentation, biological weapons development, and chemical warfare. After Japan's surrender, several members were interned at the Fushun War Criminals Management Centre and the Taiyuan War Criminals Management Centre. Many were later repatriated to Japan, where some became involved in the Association of Returnees from China and testified about their activities. Key personnel , commander of Unit 731|upright=.65 |upright=.65 Prominent members of Unit 731 included: • Lieutenant General Shirō Ishii – overall commander • Major General Masaji Kitano – commander (1942–1945) • Lieutenant Colonel Ryōichi Naitō – founder of Green Cross • Prince Tsuneyoshi Takeda • Prince Naruhiko Higashikuni • Yoshio Shinozuka – later gave testimony • Yasuji Kaneko – later gave testimony • Shigeru Fujita • Ken Yuasa • Civilian employees and students including Shigeo Ozeki, Kioyashi Mineoi, Masateru Saitō, and Yoshio Furuichi == Divisions ==

Unit 731 was divided into eight divisions: • Division 1: research on bubonic plague, cholera, anthrax, typhoid, and tuberculosis using live human subjects; for this purpose, a prison was constructed to contain around three to four hundred people • Division 2: research for biological weapons used in the field, in particular the production of devices to spread germs and parasites • Division 3: production of shells containing biological agents; stationed in Harbin • Division 4: bacteria mass-production and storage • Division 5: training of personnel • Divisions 6–8: equipment, medical, and administrative units == Facilities ==

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, or it can refer to the organization and its branches, sub-Units and their branches. The Unit 731 complex covered 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 of bubonic plague bacteria could be produced in a few days. Some of Unit 731's satellite (branch) facilities are still in use by various Chinese industrial companies. A portion has been preserved and is open to visitors as a museum. Branches Unit 731 had branches in Linkou (Branch 162), Mudanjiang, Hailin (Branch 643), Sunwu (Branch 673) and Hailar (Branch 543). While Tokyo courts acknowledged in 2002 that Unit 731 has been involved in biological warfare research, the Japanese government had made no official acknowledgment of the atrocities committed against test subjects and rejected the Chinese government's requests for DNA samples to identify human remains (including skulls and bones) found near an army medical school. == Surrender and immunity ==

Destruction of evidence As the Second World War started to come to an end, all prisoners within the compound were killed to conceal evidence, and there were no documented survivors. 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 case 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. Former Unit 731 member Hideo Shimizu stated that during the Soviet invasion of Manchuria he was instructed to eliminate evidence by burning the victims in the courtyard, collecting the leftover bones from the area, and then destroying the remains with explosives. 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 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 and 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 exclusive American access to their research on biological warfare and data from human experimentation. 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 Joseph R Massey, 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 Massey, who was probably unaware of Unit 731's activities. His reference to it at the trial is believed to have been accidental. Later in 1981, one of the last surviving members of the Tokyo Tribunal, Judge Röling, had expressed bitterness in not being made aware of the suppression of evidence of Unit 731 and wrote, "It is a bitter experience for me to be informed now that centrally ordered Japanese war criminality of the most disgusting kind was kept secret from the court by the U.S. government." American investigations into Japanese war crimes ceased when Japanese scientists began disclosing information on biological warfare. Despite the establishment of their own research program, American scientists faced a significant gap in essential knowledge regarding biological warfare. The potential value to the Americans of Japanese-provided data, encompassing human research subjects, delivery system theories, and successful field trials, was immense. However, historian Sheldon H. Harris concluded that the Japanese data failed to meet American standards, suggesting instead that the findings from the unit were of minor importance at best. Harris characterized the research results from the Japanese camp as disappointing, concurring with the assessment of Murray Sanders, who characterized the experiments as "crude" and "ineffective". Whereas the perpetrators of Unit 731 were exempt from prosecution, the U.S. held a tribunal in Yokohama in 1948 that indicted nine Japanese physician professors and medical students for conducting vivisection upon captured American pilots; two professors were sentenced to death and others to 15–20 years' imprisonment. 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 2 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 of the defendants returned to Japan by 1956. The Soviet Union built a biological weapons facility in Sverdlovsk using documentation captured from Unit 731 in Manchuria. Official silence during the American occupation of Japan As above, during the United States occupation of Japan, the members of Unit 731 and the members of other experimental units were allowed to go free. On 6 May 1947, Douglas MacArthur, the Supreme Commander of the Allied Forces, wrote to Washington in order to inform it 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". One graduate of Unit 1644, Masami Kitaoka, continued to perform experiments on unwilling Japanese subjects from 1947 to 1956. He performed his experiments while he was working for Japan's National Institute of Health Sciences. He infected prisoners with rickettsia and infected mentally-ill patients with typhus. As the chief of the unit, Shirō Ishii was granted immunity from prosecution for war crimes by the American occupation authorities, because he had provided human experimentation research materials to them. From 1948 to 1958, less than five percent of the documents were transferred onto microfilm and stored in the US National Archives before they were shipped back to Japan. Post-occupation Japanese media coverage and debate Japanese discussions of Unit 731's activity began in the 1950s, after the end of the American occupation of Japan. In 1952, an infant girl at Nagoya City Pediatric Hospital died after being infected with E. coli bacteria; the incident was publicly tied to former Unit 731 scientists. 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 1957, Japanese author Shūsaku Endō published the book The Sea and Poison about human experimentation in Fukuoka, which is thought to have been based on a real incident. In 1950, former members of Unit 731 including Masaji Kitano founded the blood bank and pharmaceutical company Green Cross, for which Murray Sanders also served as a consultant. The company became the target of a scandal in the 1980s after up to 3,000 Japanese contracted HIV through the distribution and use of its blood products, which the Pharmaceuticals and Medical Devices Agency had deemed unsafe. 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, the first direct testimony of human vivisection in China was given by Ken Yuasa. Since then, much more in depth testimony has been given in Japan. The 2001 documentary Japanese Devils'' largely consists of interviews with fourteen Unit 731 staff members taken prisoner by China and later released. Prince Mikasa, who was the younger brother of Hirohito, toured the Unit 731 headquarters in China, and wrote in his memoir that he watched films showing how Chinese prisoners were "made to march on the plains of Manchuria for poison gas experiments on humans." Significance in postwar research on bio-warfare and medicine Despite conducting scientific experiments, Unit 731 faced scrutiny regarding the usefulness of the data produced from these experiments. Despite the apparent success, Unit 731 lacked adequate scientific and engineering foundations to further maximize its effectiveness. Harris concluded that US scientists generally wanted to acquire it due to the concept of forbidden fruit, believing that lawful and ethical prohibitions could affect the outcomes of their research. Historian Till Winfried Bärnighausen criticized the overall lack of scientific rigor in many of Unit 731's experiments, but he noted some exceptions. He pointed to the mustard gas, freezing, and tuberculosis experiments as having a reliable and valid data collection process, suggesting they were conducted with greater rigor. During the war, Yoshimura Hisato conducted research at Unit 731 in China focusing on low-temperature physiology, particularly studying the mechanisms involved in frostbite. Following the war, he established the Japanese Society of Biometeorology. His research in China marked the inception of his exploration into the relationship between physiology and environmental stress. The information has been withheld by both the US and Japanese government. Official government response in Japan In 1983, the Japanese Ministry of Education asked Japanese historian Saburō Ienaga to remove a reference from one of his textbooks that stated Unit 731 conducted experiments on thousands of Chinese. The ministry alleged that no academic research supported the claim. In 1984, Japanese historian Tsuneishi Keiichi translated and published over 4,000 pages of U.S. documents on Japanese biological warfare. The ministry backed down after new studies were published in Japan and important evidence surfaced in the United States. Japanese history textbooks usually contain references to Unit 731, but the textbooks do not provide specific details about the activities conducted at the facility. 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, 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 levels of the Japanese court system found the suit baseless. No findings of fact were made about the existence of human experimentation. 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. He rejected victims' compensation claims on the grounds that they had already been settled by international peace treaties. In October 2003, a member of Japan's House of Representatives filed an inquiry. Prime Minister Junichiro Koizumi responded that the Japanese government did not then possess any records related to Unit 731, but recognized the gravity of the matter and would publicize any records 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. Abroad After World War II, the Office of Special Investigations created a watchlist of suspected Axis collaborators and persecutors banned from entering the United States. While over 60,000 names were added to the watchlist, fewer than 100 Japanese participants were identified. 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: • While most documents captured by the US in Europe were microfilmed before being returned to their respective governments, the Department of Defense decided not to microfilm its vast collection of documents before returning them to the Japanese government. • 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, were largely cooperative. The cumulative effect was that information needed to identify these individuals became, in effect, impossible to recover. == In popular culture ==

Print media • Tricky Twenty-Two (2015), novel by Janet Evanovich. Features a villainous biology professor attempting to recreate Unit 731's plague dispersals. • The Solomon Curse (2015), novel by Clive Cussler and Russell Blake. Includes a subplot about secret human experimentation linked to Unit 731. • My Hero Academia (2014–2024), manga by Kōhei Horikoshi. A character originally named "Shiga Maruta" sparked backlash for referencing Unit 731's human test subjects. The name was later changed. • Crisis in the Ashes (1999), novel by William W. Johnstone. Features the grandson of a Unit 731 scientist using plague as a weapon. • The Collector – Unit 731 (2021), comic miniseries by Dark Horse Comics, written by Rod Monteiro and illustrated by Will Conrad. Follows a POW captured and experimented on by Unit 731. • Inheritors (2020), short story collection by Asako Serizawa. Includes "Train to Harbin," about a Japanese doctor reflecting on his wartime crimes. • The English Führer (2023), novel by Rory Clements. Involves biological weapons developed by Unit 731. • The Ninth Artifact: The Artifact Series #9 (2025), novel by David Collins. The chapter entitled "The Spiders Return" mentions "the Japanese vivisection experimentation on prisoners in World War II. Those were stains on the glorious history." Film • Men Behind the Sun (1988), Hong Kong film by Tun Fei Mou. Graphic dramatization of Unit 731's activities. • Unit 731: Laboratory of the Devil (1992), Hong Kong film by Godfrey Ho. Depicts atrocities committed at Unit 731. • Men Behind the Sun 3: A Narrow Escape (1994), Hong Kong film by Godfrey Ho. Presents Unit 731 destroying all evidence before escaping from China. • 731: Two Versions of Hell (2007), documentary by James T. Hong. Presents Chinese and Japanese perspectives on Unit 731. • Philosophy of a Knife (2008), Russian experimental film by Andrey Iskanov. Focuses on the horrors of Unit 731. • Dead Mine (2012), Indonesian film by Steven Sheil. Features a fictional offshoot of Unit 731's research. • Dongju: The Portrait of a Poet (2016), South Korean film by Lee Jun-ik. Depicts Korean poet Yun Dong-ju who died under suspicious conditions linked to experimentation. • Wife of a Spy (2020), Japanese film by Kiyoshi Kurosawa. Involves secret footage exposing Unit 731's work; won the Silver Lion for Best Direction at Venice. • Evil Unbound/731 (2025), Chinese film by Linshan Zhao. Dramatization of Unit 731's wartime activities. • Site (2025), United States film by Jason Eric Perlman. Science fiction about entangled timelines and lives, particularly a family imprisoned by Unit 731. • ''Man's Inhumanity to Man'' (Chinese: 反人类暴行) (2025), Chinese film drama by Lao Suan. Plot is based on Unit 731. Music • "The Breeding House" (1994), song by Bruce Dickinson. Explores unethical experimentation themes. • "Unit 731" (2009), song by Slayer. References atrocities committed by Unit 731. • "Unit 731" (2011) , song by brandkommando. on the Compilation album Philosophy Of A Knife. • "And You Will Beg for Our Secrets" (2016), song by Anaal Nathrakh. Inspired by wartime human experimentation. • "The New Eternity" (2018), song by Silent Planet. Explores dehumanization and historical atrocities. • "Maruta" (2009), song by South Korean metal band Sad Legend. References the code name for Unit 731 victims. • "Unit 731" (2021), track by German dubstep producer KROWW. Named after the infamous unit. • Maruta, American grindcore band. Named after the term "maruta" used for test subjects in Unit 731. Television • ''Inside Unit 731: Japan's Secret Human Experiments'' (2026) is a two-part documentary series from Channel NewsAsia. • Unit 731 – Did the Emperor Know? (1985), documentary by Television South. Investigates Imperial Japan's knowledge of Unit 731. • "731" (1995), episode of The X-Files. Depicts continuation of Unit 731's experiments under a covert U.S. program. • "Let It Burn" (2007), episode of ReGenesis. Connects anthrax and glanders outbreaks to Unit 731's wartime work. • "The 40th Floor" (2011), episode of Warehouse 13. Features a cursed medal linked to Unit 731. • Concrete Revolutio (2015), anime series. Features fictional superhuman experiments paralleling Unit 731. • 731 () (2015), five-part CCTV documentary. Chronicles Unit 731's crimes and postwar legacy. • The Truth of Unit 731: Elite Medical Students and Human Experiments (2017), NHK documentary. Features interviews and recovered documentation from Unit 731 personnel. • "General Shiro" (2018), episode of The Blacklist. Refers to Shirō Ishii and echoes Unit 731's activities. • Kamen Rider Black Sun (2022), Japanese Amazon Prime series. Features fictional experiments linked to Unit 731, set in 1936. • Gyeongseong Creature (2023), Korean drama on Netflix. Depicts biowarfare research during Japanese occupation of Gyeongseong. Video games • ''Spooky's Jump Scare Mansion'' (2015). Features enemies implied to originate from Unit 731–style experimentation. • Call of Duty: Black Ops III (2015), Zombies mode. Introduces "Division 9", modeled on Unit 731, with the KT-4 weapon labeled "731細菌戦の研究機関" ("Research Institution 731 of Bacterial Warfare"). == See also ==