Unit 731: Firsthand Accounts of Japan's Wartime Human Experimentation Program

by Hal Gold

The Epidemic Prevention and Water Purification Department of the Kwantung Army—popularly known by its codename “Manchurian Unit No. 731” or simply “Unit 731”—was a secret biological weapons research and development unit maintained by the Imperial Japanese Army in the outskirts of Harbin in Japanese-controlled Manchuria, northeastern China, for the duration of World War II in Asia and the Pacific.

the use of thousands of human guinea pigs for medical experimentation. The vast majority of these human subjects are believed to have been Chinese nationals taken prisoner over the course of the Second Sino-Japanese war that originated in the Japanese invasion of Manchuria in September 1931, and that grew to full-blown warfare in July 1937. Men, women, and children of other nationalities were also used for experiments, and babies born to women in Unit 731’s custody apparently were not spared either.

This book outlines medical experimentation that was conducted by Unit 731, heinous acts including injecting human subjects with pathogens; monitoring the progress of diseases by drawing blood samples from and conducting vivisection on live individuals; exposing human subjects to infected insects in an open-air testing field; infecting a healthy individual with venereal disease by way of forced sexual intercourse with a carrier of venereal disease; causing frostbite on limbs by exposing them to water and cold air in a sub-zero temperature environment; and collecting human specimens—organs, body parts, and even entire bodies of human subjects—which were subsequently kept at Unit 731’s lab and the army medical facilities in Tokyo.

The Imperial Japanese Army also set up other medical units in Beijing, Nanjing, Guangzhou, and Singapore, so that biological weapons research and development could be carried forth in the broader region of Asia and the Pacific under Japanese military control.

One might expect, under those circumstances, that the members of Unit 731 would have been among the first for the Allied authorities to name as war criminals and to put on trial. But that, in fact, was not the case. Unit 731 rather became a pawn of cold-war politics as the U.S. government prioritized racing against the Soviet Union in securing the biological weapons’ knowledge that Unit 731 had amassed and, to that end, shielding from war crimes prosecution the medical unit’s former members, including its chief, Surgeon General Ishii Shiro.

The Soviet authorities, for their part, had their own share of interests in gaining access to Unit 731’s secretive information, but they appeared also focused on using it as a propaganda tool to be deployed against the United States. Having failed in getting the inter-Allied prosecuting agency at the International Military Tribunal for the Far East (IMTFE, 1946–48) to incorporate the evidence of Unit 731 in the case against major Japanese war criminals, the Soviet government set up a special military tribunal at Khabarovsk in December 1949 to hold a joint trial of 12 former Japanese army officers on criminal charges relating to Unit 731’s wartime activities.

After the war, he published a book titled The Real Triumph of Japan: the Conquest of the Silent Foe. In it, he writes that the history of warfare for centuries has proven that in prolonged campaigns the first, or open enemy, kills twenty per cent of the total mortality in the conflict, whilst the second, or silent enemy, kills eighty … This dreadful and unnecessary sacrifice of life, especially among the Anglo-Saxon races, is the most ghastly proposition of modern war, and the Japanese have gone a long way toward conquering or eliminating it … I unhesitatingly assert that the greatest conquests of Japan have been in the humanities of war, in the stopping of the needless sacrifice of life through preventable disease … In our war with Mexico, the proportion of losses was about three from disease to one from bullets, and in our great Civil War nearly the same proportion obtained … No lessons seem to have been learned from these frightful experiences, for later statistics show no improvement. In the French Campaign in Madagascar in 1894 fourteen thousand men were sent to the front, of whom twenty-nine were killed in action and seven thousand perished from preventable disease. In the Boer War in South Africa the English losses from disease were simply frightful, greater than even our Civil War record. But the crowning piece of imbecility was reserved for our war with Spain, where, in 1898, fourteen were needlessly sacrificed to ignorance and incompetency for every one who died ...

The author points out how in Japan’s war with China in 1894, the Japanese ratio of losses from disease was about the same as that suffered by American soldiers suffered in two of the wars cited above. The experience gained from that clash in Manchuria, however, was put to good use a decade later, and the Japanese army’s ratio of combat casualties to those caused by disease turned around dramatically. Noting Japan’s success, he writes, “Only one and two-tenths percent of the entire army died of sickness or disease. Only one and one-half died of gunshot wounds, although twenty-four percent were wounded … This record is, I believe, unparalleled and unapproached in the annals of war.”

“Japan put into use the most elaborate and effective system of sanitation that has ever been practiced in war,” he wrote. For instance, “every hospital throughout Japan, and every base and field hospital in Manchuria, has its bacteriological laboratory.” The author praises the work done by “Japan’s corps of trained experts with the microscope, that the dread phantom of disease might be intercepted.” He describes the use of X-ray equipment at hospitals, and even portable X-ray machines in field hospitals. In contrast, war correspondents recorded a statement by one of the Russian officers caught in the siege of Port Arthur: “Our principal enemies are the scurvy and 11-inch shells, which know no obstacle and against which there is no protection.” (Eleven-inch...

The Japanese success in minimizing deaths from illness proved that they were correct in attaching equal priority to germs and bullets, and soon after the war’s end, a Department of Field Disease Prevention was established. It was a natural outgrowth of the lessons learned in Manchuria and a peacetime continuation of what the American medical observer termed “the most elaborate and effective system of sanitation ever practiced in war.” Commendable though this move was, though, it had its dark side. The original bacteriological aims of Japan were soon to be warped in the direction of causing, rather than preventing and curing, disease. And the fiber of the high morality of Japanese troops, praised by the American surgeon and foreign journalists and observers in Manchuria, would be shred and rewoven into racist ugliness at the hands of the Japanese military and medical elites.

Japan was a signatory to the Geneva Convention of 1925, which led to the prohibition of biological and chemical warfare. As a specialist in bacteria-related fields, Ishii actually found this development encouraging; he reasoned that if something were bad enough to be outlawed, then it must certainly be effective.

One rumor told of a young boy who was curious about the Fortress and went out to have a look. His body was found the next day; he had been killed by gunfire. But even walls and guns could not keep rumors of cries of pain and anguish inside the Fortress from circulating through the village. And, by 1936, it was well known among the Chinese that this was not just a prison, but a production facility for bacteria, and a murder shop.

One of these tests consisted of taking blood samples. At least five hundred cubic centimeters was drawn at two- to three-day intervals. Some of the victims became progressively debilitated and wasted. Still, the blood drainage continued. Careful records were kept, and these experiments smack more of a combination of professional curiosity than of actual science: a simple, childlike curiosity to see how far a human being can be squeezed of blood until death occurs. Not all were drained to the point of death, though. Many were injected with poison when they could no longer serve as lab materials. Sometimes, when a subject was too weak to offer physical resistance, he would be killed with a blow to the head with an axe. The brain might then be used for further research.

It is said that the life expectancy of prisoners at the Fortress was a maximum of one month.

An earlier experiment tried to determine how long a person could live on just water. Food was withheld from prisoners, and some were given only ordinary water, while others received only distilled w...

In all the gruesome professionalism that built the legacy of Unit 731, there was one touch of sardonic humor. As the massive Pingfang installation was under construction, local people began to ask what it was. The glib answer supplied was that the Japanese were building a lumber mill. Regarding this reply, one of the researchers joked privately, “And the people are the logs.” From then on, the Japanese term for log, maruta, was used to speak of the prisoners whose last days were spent being tom apart or gassed by Japanese researchers. It is surprising how few Japanese realize the origin of this term, though the word itself never fails to come up when Unit 731 is discussed. The expression smacks of a racial attitude not even up to the level of disdain.

Human experimentation gave researchers their first chance to actually examine the organs of a living person at will to see the progress of a disease. Vivisection was a new experience for the doctors of Japan. One former unit member explained that “the results of the effects of infection cannot be obtained accurately once the person dies because putrefactive bacteria set in. Putrefactive bacteria are stronger than plague germs. So, for obtaining accurate results, it is important whether the subject is alive or not.”

The research methods in Manchuria allowed doctors to induce diseases and examine their effects on organs at the first stages. Researchers worked with interpreters to ask about emerging symptoms, and took subjects out of cells at what they judged to be the time for optimum results. Anesthesia was optional. According to a former unit member: “As soon as the symptoms were observed, the prisoner was taken from his cell and into the dissection room. He was stripped and placed on the table, screaming, trying to fight back. He was strapped down, still screaming frightfully. One of the doctors stuffed a towel into his mouth, then with one quick slice of the scalpel he was opened up.” Even with the intestines and organs exposed, a person does not die immediately. It is the same physical situation as ordinary surgery under anesthesia in which a person is operated on and restored.

Witnesses at vivisections report that the victim usually lets out a horrible scream when the cut is made, and that the voice stops soon after that. The researchers then conduct their examination of the organs, remove the ones that they want for study, then discard what is left of the body. Somewhere ...

He spoke of the time he was working on a woman victim who had awakened from anesthesia while being vivisected. The woman interviewing him asked what happened. “She opened her eyes.” “And then?” “She hollered.” “What did she say?” Kurumizawa could not answer, then began weeping feebly and murmured, “I don’t want to think about it again.” The interviewee apologized, waited a few seconds, and tried again for an answer. He gave it through sobs. “She said, ‘It’s all right to kill me, but please spare my child’s life.’” Four months after this interview, Kurumizawa died. A

Women were captured and experimented upon, and a large number of babies were born in captivity. Some were born to women who had been brought in while pregnant. Others were born to women who became pregnant in forced sex acts during tests investigating the transmission of venereal disease.

These materials were made available not just to the army hospital, but to researchers throughout Japan. This gave universities the chance to study diseases not then in Japan, such as plague, cholera, and epidemic hemorrhagic fever (EHF). In this way, Unit 731 was performing the service of human experimentation for the entire Japanese medical community—civilian and military, public and confidential.

The contents outlined above appeared in an abstract in the medical journal. A medical doctor or researcher reading the manner in which the disease develops, and particularly the fever characteristics, should be able to recognize the subjects not as monkeys but humans. Most obvious is the account of body temperature: the “monkeys” recorded temperatures of up to 40.2 degrees Celsius. Even the sickest monkey’s body temperature will never reach that point. Rather, the fever reported was in the range of where it would be for very sick human beings. Moreover, as Professor Tsuneishi points out, the test subjects used in this research were listed simply as “monkeys.” Failure to identify the species of an animal in an experiment lowers the value of the paper reporting its results.

Where monkeys were actually used, it was common practice to identify the type. Thus, it was an open secret that the simple and un-scientific use of the term “monkey” by itself was a code which meant that the subjects were humans. The medical community knew this. The journal knew this. The readiness with which Kitano publicized this transparent sham—and its acceptance by Japan’s medical community at large—is a sad testament to the lack of conflict between the ethical standards of the medical world in Japan and those of Unit 731.

In October 1940 a plague attack was conducted against the Kaimingjie area of the port city of Ningbo. This was a joint operation by Unit 731 and one of its affiliates, Nanjing-based Unit 1644. In this operation, plague germs mixed with wheat, com, cloth scraps, and cotton were dropped from the air.

Qian Guifa, a resident of the area attacked, was fourteen years old at the time and working in a tofu shop. He was infected, but managed to recover, and it is said that he is the only living person today who can bear witness to the Japanese biological warfare experiment at Ningbo.

His testimony has been recorded in video documentary and in printed literature in Japan. He recounts: “One day, a Japanese plane flew over and kept circling. Then, it dropped something that looked like smoke. It was wheat flour and corn and other things. The next day people started getting sick. Three days later, the tofu shop owner’s two children were dead, and other people were getting sick and dying. Nobody could understand what had happened. My own family died, one after the other. There was misery all around. “E...

More than one hundred persons died within a few days after the attack. The affected area was closed to the public and remained sealed off until the 1960s, when it was ascertained positively that there was no further risk of infection. Government records still existing in China show the results of the plague attacks and the deaths which followed. A Chinese speciali...

“On the twenty-ninth, three days after the Japanese plane came, I entered the Ningbo area that had been attacked. The first thing I did was separate the people seriously affected, those lightly affected, and the healthy ones. Then, I encircled the infected area of the attack zone with a wall about a meter deep and a meter and a half high, so that rats could not escape. Six hundred people were moved south. When November came, we burned everything in the enclosed area, and in this way we stopped the plague from spreading. According to my records, ninety-seven peopl...

I was fifteen years old at the time, and I remember everything clearly. The Japanese plane spread something that looked like smoke. A few days later we found dead rats all over the village. At the same time, people came down with high fevers and aches in the lymph nodes. Every day, people died. Crying could be heard all through the village. My mother and father—in all, eight people in my family—died. I was the only one in my family left. My mother had a high fever all day. She was crying for water, and clawing at her throat. Then, she let out a roar like a lion, and died before my eyes. Altogether, three hundred eighty people in the village died. At times, as many as twenty people died in one day. As soon as the first people started dying, Japanese came into the village wearing protective clothi...

Professor Tsuneishi has conducted nearly two decades of research into the activities of Unit 731, and his knowledge of its history and activities is encyclopedic. Of everything that went on in the prison cells, on the dissection tables, and in the research labs, he has expressed his opinion that the cruelest experiments of all were those which concerned frostbite research.

People were taken from prison into below-freezing temperatures. They were tied up, with their arms bared and soaked with water. Water was poured over the arms regularly; sometimes the ice that formed on them would be chipped away and water again poured over. The researcher would strike the limbs regularly with a club. When an arm made a sound like a wooden board’s being hit, this indicated that the limb was frozen through, and from there different methods of treatments were tested. Legs and feet were exposed to similar treatment. Temperatures in Manchuria can reach as low as minus twenty to thirty degrees Celsius. Some of the tests were conducted outdoors in these winter conditions. At times, electric fans were used to speed the freezing. At Pingfang, Yoshimura had his own large refrigerator lab that allowed him to freeze subjects all year round and reach even lower temperatures than out in the open—temperatures that reached as low as minus seventy degrees Celsius.

Some experiments resulted in the flesh and muscle falling from the bones. Others left the bones so brittle that they were shattered by the blows from the clubs. Either way, the eventual result was the same: gangrene and the rotting away of extremities. Several former Unit 731 members have commented on seeing victims of the experiments. They reported that the victims “had no hands … no feet.” A miniature model of a frostbite experiment was displayed at the Unit 731 exhibitions: It depicts an experiment being performed on a Russian prisoner. Chinese were also used as fodder for the freezing experiments, and some of the victims were women. Yoshimura conducted his frostbite experiments right up until the end of the war. One of the discoveries for which Yoshimura subsequently became famous was that the previously standard treatment of rubbing frozen limbs until they thawed was not the most efficient way of restoring them. Through trial and error, he showed that the best treatment was placing the affected parts in warm water between thirty-seven degrees (normal human body temperature) and forty degrees Celsius. There is no way to count the number of people and human limbs he consumed in arriving at this finding.

Recent evidence points to a plan to carry Japan’s biological warfare program to the United States itself.

When the planes landed, they came alongside their mother ships, and they were hoisted back aboard with winches. The I-400 submarine, the only ship of its class, was a large sub capable of carrying three planes. This boat was earmarked for the attack on America’s west coast. The sub had a displacement of 3,530 tons, an underwater speed of six and a half knots, and a surface speed of eighteen knots. It was diesel-powered and snorkel-equipped, so that its combustion engines could run even while the boat was submerged. This characteristic enabled it to use one of its two engines for propulsion, while it charged its batteries with the other. At sixteen knots on the surface, it had a normal range of thirty-one thousand nautical miles. Its range could be extended by filling the ballast tanks with fuel oil instead of water. Filling the ballast tanks would, of course, mean that the sub could not surface until after a sufficient amount of fuel had been consumed, but Allied air and naval presence in the Pacific in the early part of 1945 would make submerged travel prudent at any rate. Reaching the American mainland seemed to be no problem, at least as far as technology was concerned.

All discussion of the ultra-secret plan, first proposed toward the end of December 1944, was confined to a special tactical room set aside at the headquarters of the Naval General Staff in Hibiya, Tokyo. There were two main drawbacks to conducting this operation as a purely naval venture. One was a lack of data regarding the intended pathogens. The other was a lack of the pathogens themselves. For this, the nation’s highest authority on biological warfare was called in, and Ishii became special advisor to the top army man in the project, Colonel Hattori Takushiro. One might imagine Ishii’s anticipation as he envisioned American high-density population centers filled with agony, with citizens turning to blackened corpses. It would be a larger-scale success of—indeed a capstone to—his attacks on Chinese cities and villages.

The project moved forward from a foundation of biological warfare intelligence provided by Ishii and Unit 731, and the plan was finalized on March 26, 1945. Then, at the last moment, General Umezu Yoshijiro, Chief of the General Staff, stepped in and ordered the plan scrapped. He reasoned that “if bacteriological warfare is conducted, it will grow from the dimension of war between Japan and America to an endless battle of humanity against bacteria. Japan will earn the derision of the world.”

Interestingly, about two weeks before the finalization of the plan, America brought a new weapon into the war with an incendiary attack on a large, lower-class neighborhood of Tokyo. Even among the almost continuous air raids over Japan, the Great Tokyo Air Raid had been the most devastating so far, with an estimated one hundred thousand civilians burned to death by a combination of conventional incendiaries and America’s new contribution to modern weaponry, napalm. Even this failed to deter Umezu from his veto of a germ attack on America. General Umezu was later given the inglorious duty of representing Japan’s army in signing the instrument of capitulation aboard the U.S.S. Missouri. At first he refused, then agreed to go only if it were considered a direct order from the emperor. Umezu was later tried for and found guilty of war crimes at the Tokyo War Crimes Trials. His single-handed prevention of the bacteriological attack on America never surfaced there.

The manuscript said, in essence, that the Japanese were involved in biological warfare.” The document, Sanders stated, gave the line of command of the Japanese military, with all the departments “implicated, plus or minus.” Obviously, as much as America wanted the information, the Japanese had an equal interest in avoiding the “justice” of the Soviet legal system, at whose hands their fate would be easy enough to predict. His gambit appeared to have succeeded.

Sanders took the document to General Douglas MacArthur, the Supreme Commander for the Allied Powers (SCAP), and from there the balance of options was weighed. There was information that America wanted, and on an exclusive basis. That would mean America’s turning its back on the forthcoming war crimes trials and striking a deal, independently of the judiciary proceedings, with the men who had the data. Sanders recalls MacArthur as having said, “Well, if you feel that you cannot draw out the information, we are not given to torture.” So, deprived of the stick of physical duress, the American microbiologist went back to Naito with a carrot instead. MacArthur would assure Naito that in exchange for the information, the informants would not be brought to trial. “This made a deep impression, and the data came in waves after that … we could hardly keep up with it.”

This shows that the proposal—made with the involvement of the American president—to grant immunity from war crimes was already on the table less than two months after the war’s end.

to borrow the expression that that president himself made famous—on the decision not to prosecute the former members of Unit 731, the buck stopped right at Harry S. Truman’s desk.

America’s decision not to prosecute Ishii and his men was not the final word on the matter, however. In July 1948, the Soviet army newspaper Red Star carried an article by a Col. Galkin, special correspondent on the newspaper for Japanese biological warfare. According to the article, the Japanese were preparing to use biological warfare on a large scale, and they had a huge bacteriological center in Manchuria. Galkin’s piece did not state that Japanese biological warfare was intended for use against his country, and instead specifically pointed out that it was for use against China, the United States, and Britain. The Red Star article also did not mention Soviet citizens as victims of human experimentation. Still more surprising, the Soviet article did not mention the imperial order which had allegedly led to the establishment of the labs. There was only mention of Prince Mikasa acting as the emperor’s representative.

Some time later, however, a different version of events emerged from behind the Iron Curtain. In December 1949, in the city of Khabarovsk, on the railway line north of Vladivostok, twelve former members of Ishii’s organization were placed on trial for war crimes. Soviet press reports told the U.S. State Department of the first installment of the trial results, and included “confessions” by several Japanese that the Japanese General Staff and War Ministry had set up secret labs in Manchuria in 1935–1936, for preparation and execution of bacteriological warfare. During court testimony, these were said to have been established on direct order from Emperor Hirohito. The Soviet account goes on to state that the Soviet Union was one of the intended targets of Japan’s biological warfare efforts, that Soviet citizens were among th...

Commenting further on connections between AIDS and biological warfare, Dr. Yamaguchi adds his voice to the chorus of those who find it hard to believe the orthodox explanation that the disease started with monkeys. It is much easier, he says, to think that it was developed in Fort Detrick as part of their ongoing biological warfare program, after which it somehow leaked out. A researcher at Fort Detrick was said to have remarked to the effect that, within ten years, the U.S. would have developed a biological weapon that would be more devastating than anything to date. Just ten years after that statement, the first AIDS case appeared. The Fort Detrick origin, says Yamaguchi, is a much more scientifically realistic explanation.

Each of Japan’s kamikaze pilots was given a drink of Imperial saké before leaving on their missions. A Unit 731 member once told me that “that saké is laced with a stimulant that was developed in Unit 731.” Afterwards, I heard that the stimulant suppresses fear and agitates the pilots to throw themselves into the attack.

The main ingredient of the defoliant used in the Vietnam War was dioxin. Of course, Unit 731 conducted basic research using dioxin. America took those research records and used them.

It is said that there were twenty million victims of the war in China. But only ten to twenty percent of these were killed in gunfire exchange. Most—non-resisting old people, women, and children—were captured and slaughtered. Prisoners of war could not be taken to the front or allowed to escape, so they were killed in the manner of the Rape of Nanjing.

After the war, there were fantastic payments to former Unit 731 members. Some people got up to two million yen. That kind of money was unheard of in those days, around 1948 or 1949. It was unbelievable. Maybe the American army brought it in: I don’t know where it came from, but, almost without exception, anyone connected in any way at all with Unit 731 got something. That was the best-paying job there was. A lot of university professors were connected with Unit 731. Especially upper-level people, like in the Ministry of Health and Welfare and those concerned with vaccines. They all had some connection with the Ishii unit in some way. They never said anything about it, but they all received pay for working there. Those are the people who built the foundation of today’s Japan.