Unit 731 was the code name (tsūshōgō) of an Imperial Japanese Army unit officially known as the Kempeitai Political Department and Epidemic Prevention Research Laboratory. It was initially set up under the Kempeatai military police of the Empire Of Japan to develop weapons of mass destruction for potential use against Chinese, and possibly Soviet forces.
Unit 731 was based at the Pingfang district of Harbin, the largest city in the Japanese puppet state of Manchukuo (now Northeast China).
(Pictured right: Shro Ishii, commander of Unit 731).
More than ten thousand people, from which around 600 every year were provided by the Kempeitai, were subjects of the experimentation conducted by Unit 731.
More than 95 percent of the victims who died in the camp based in Pingfang were Chinese and Korean, including both civilian and military. The remaining 5 percent were South East Asians and Pacific Islanders, at the time colonies of the Empire Of Japan, and a small number of the prisoners of war from the Allies of World War II the Crimes of Bacteriological Warfare, the number of people killed by the Imperial Japanese Army germ warfare and human experiments is around 580,000. According to other sources, the use of biological weapons researched in Unit 731's bio weapons and chemical weapons programs resulted in possibly as many as 200,000 deaths of military personnel and civilians in China.
Unit 731 was the headquarters of many subsidiary units used by the Japanese to research biological warfare; other units included Unit 516 (Qiqihar), Unit 543 (Hailar), Unit 773 (Songo unit), Unit 100 (Changchun), Unit Ei 1644 (Nanjing), Unit 1855 (Beijing), Unit 8604 (Guangzhou), Unit 200 (Manchuria) and Unit 9420 (Singapore).
Many of the scientists involved in Unit 731 went on to prominent careers in post-war politics, academia, business, and medicine. Some were arrested by Soviet forces and tried at the Khabarovsk War Crime Trials; others surrendered to the American Forces.
On 6 May 1947, Douglas MacArthur, as Supreme Commander of the Allied Forces, wrote to Washington that "additional data, possibly will be retained in intelligence channels and will not be employed as 'War Crimes' evidence." The deal was concluded in 1948.
Because of their brutality, Unit 731's actions have since been declared by the United Nations to have been crimes against humanity.
In 1932, General Shiro Ishii (石井四郎 Ishii Shirō), chief medical officer of the Japanese Army and protégé of Army Minister Sadao Araki was placed in command of the Army Epidemic Prevention Research Laboratory. He and his men built the Zhong Ma Prison Camp (whose main building was known locally as the Zhongma Fortress), a prison/experimentation camp in Beiyinhe, a village 100 kilometers south of Harbin on the South Manchurian Railway.
Ishii organized a secret research group, the "Togo Unit", for the conduct of various chemical and biological investigations. A jailbreak and later explosion (believed to be an attack) in 1935 led Ishii to shut down Zhongma Fortress. He moved to Pingfang, approximately 24 kilometers south of Harbin, to set up a new and much larger facility.
In 1936, Hirohito authorized, by imperial decree, the expansion of this unit and its integration into the Kwantung Army as the Epidemic Prevention Department. It was divided at the same time into the "Ishii Unit" and "Wakamatsu Unit" with a base in Hsinking. From August 1940, all these 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.
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?). This term originated as a joke on the part of the staff due to the fact that the official cover story for the facility given to the local authorities was that it was a lumber mill.
The test subjects were selected to give a wide cross section of the population and included common criminals, captured bandits and anti-Japanese partisans, political prisoners, and also people rounded up by the secret police for alleged "suspicious activities". They included infants, the elderly, and pregnant women.
Prisoners of war were subjected to vivisection without anesthesia. Vivisection's were performed on prisoners after infecting them with various diseases. Scientists performed invasive surgery on prisoners, removing organs to study the effects of disease on the human body. These were conducted while the patients were alive because it was feared that the decomposition process would affect the results. The infected and vivisected prisoners included men, women, children, and infants.
Vivisection's were also performed on pregnant women, sometimes impregnated by doctors, and the fetus removed.
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' limbs were frozen and amputated, while others had limbs frozen then thawed to study the effects of the resultant untreated gangrene and rotting.
Some prisoners had their stomachs surgically removed and the esophagus reattached to the intestines.
Parts of the brain, lungs, liver, etc. were removed from some prisoners.
In 2007, Doctor Ken Yuasa testified to the Japan Times that, "I was afraid during my first vivisection, but the second time around, it was much easier. By the third time, I was willing to do it." He believes at least 1,000 people, including surgeons, were involved in vivisection's over mainland China.
Flame throwers were tested on humans.
Humans were tied to stakes and used as targets to test germ releasing bombs, chemical germ-weapons, and explosive bombs.
Germ warfare attacks
To study the effects of untreated venereal diseases, male and female prisoners were deliberately infected with syphilis and gonorrhea, then studied.
Prisoners were infested with fleas in order to acquire large quantities of disease-carrying fleas for the purposes of studying the viability of germ warfare.
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 around 400,000 Chinese civilians.
Tularemia was tested on Chinese civilians.
Unit 731 and its affiliated units (Unit 1644, Unit 100, et cetera) were involved in research, development, and experimental deployment of epidemic-creating bio warfare weapons in assaults against the Chinese populace (both civilian and military) throughout World War II. Plague-infested fleas, bred in the laboratories of Unit 731 and Unit 1644, were spread by low-flying airplanes upon Chinese cities, coastal Ningbo in 1940, and Changde, Hunan Province, in 1941. This military aerial spraying killed thousands of people with bubonic plague epidemics.
Prisoners were subjected to other torturous experiments such as:
being hung upside down to see how long it would take for them to choke to death.
having air injected into their arteries to determine the time until the onset of embolism.
being deprived of food and water to determine the length of time until death.
being placed into high-pressure chambers until death.
being exposed to extreme temperatures and developing frostbite to determine how long humans could survive with such an affliction, and to determine the effects of rotting and gangrene on human flesh.
having experiments performed upon prisoners to determine the relationship between temperature, burns, and human survival.
being placed into centrifuges and spun until dead.
having animal blood injected and the effects studied.
being exposed to lethal doses of x-rays.
having various chemical weapons tested on prisoners inside gas chambers.
being injected with sea water to determine if it could be a substitute for saline.
being buried alive.
Japanese scientists performed tests on prisoners with 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 the bubonic plague. Some of these bombs were designed with ceramic (porcelain) shells, an idea proposed by Ishii in 1938.
These bombs enabled Japanese soldiers to launch biological attacks, infecting agriculture, reservoirs, wells, and other areas with anthrax, plague-carrier fleas, typhoid, dysentery, cholera, and other deadly pathogens. During biological bomb experiments, scientists 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 out to unsuspecting victims and children, and the results examined.
The Unit 731 complex covered six square kilometers 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, 6 cauldrons to produce various chemicals, and around 1,800 containers to produce biological agents. Approximately 30 kg of bubonic plague bacteria could be produced in several days.
Some of Unit 731's satellite facilities are in use by various Chinese industrial concerns. A portion has been preserved and is open to visitors as a War Crimes Museum. (Pictured left: Information sign at the site today).
Tons of biological weapons (and some chemicals) were stored in various places in northeastern China throughout the war. The Japanese attempted to destroy evidence of the facilities after disbanding. 29 people were hospitalized in August, 2003 after a construction crew in Heilongjiang inadvertently dug up chemical shells that had been buried deep in the soil more than 50 years before.
Operations and experiments continued until the end of the war. Ishii had wanted to use biological weapons in the Pacific conflict since May 1944, but his attempts were repeatedly foiled by poor planning and Allied intervention.
With the Russian invasion of Manchukuo and Mengjiang in August 1945, the unit had to abandon their work in haste. The members and their families fled to Japan.
Ishii ordered every member of the group "to take the secret to the grave", threatening to find them if they failed, and prohibiting any of them from going into public work back in Japan. Potassium cyanide vials were issued for use in the event that the remaining personnel were captured.
Skeleton crews of Ishii's Japanese troops blew the compound up in the final days of the war to destroy evidence of their activities, but most were so well constructed that they survived somewhat intact as a testimony to what had happened there.
After Imperial Japan surrendered to the Allies in 1945, Douglas MacArthur became the Supreme Commander of the Allied Powers, rebuilding Japan during the Allied occupation. MacArthur secretly granted immunity to the physicians of Unit 731 in exchange for providing America with their research on biological warfare. American occupation authorities monitored the activities of former unit members, including reading and censoring their mail.
The United States believed that the research data was valuable because the Allies had never conducted or condoned such experiments on humans due to moral and political revulsion. The United States also did not want other nations, particularly the Soviet Union, to acquire data on biological weapons, not to mention the military benefits of such research.
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 counselor 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 likely aware 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 the prosecuted for war crimes including germ warfare was General Otozo Yamada, the commander-in-chief of the million-man Kwantung Army occupying Manchuria.
Many Russian civilians, including women and children, and Soviet POWs held by Japan were killed in chemical and biological warfare experiments by Unit 731, along with the Chinese people, American POWs, Russian and other nationalities. The trial of those captured Japanese perpetrators was held in Khabarovsk in December 1949.