One of the lesser known atrocities of the century, known by Unit 731 remained one of the closely guarded secret of WWII.

During the Sino-Japanese Wars and World War 2, the Imperial Japanese Army performed covert human experimentation in Pingfang, China. The official name for the research and development unit was the “Epidemic Prevention and Water Purification Department of the Kwantung Army”

Originally, this unit was set up under the Kempeitai military police, but Surgeon General Shiro Ishii took control. The actual facility where the tests occurred was built 1934–39. It took the name “Unit 731” in 1941.

This was a unit of the Japanese Imperial Army that carried out lethal human experimentation (biological and chemical warfare) during the second Sino-Japanese war. At least 250,000 people died in Unit 731. Human experiments conducted here were numerous. It included vivisection of live people (often pregnant women), cutting off the limbs of prisoners and attaching them to another part of their body, men and women infected with various diseases to follow the effects of untreated diseases, many of them had parts of their bodies frozen and were refused treatment for gangrene. Unit 731 was notorious for it’s experiments carried out on humans and the worst part is that Shiro Ishii (commander of the unit) wasn’t convicted for those crimes.

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Shiro Ishii, Commander of Unit 731


Japanese scientists and doctors would inject certain prisoners with various diseases. After a set period of time, the prisoner would be thrown on an operating table and cut open WHILE STILL ALIVE and without anesthesia. Often, organs would be removed during the vivisection to further study the disease’s progression. Prisoners also had limbs amputated and reattached to study blood loss. Often, the limbs would be reattached to the opposite side of the body. The scientists and doctors also removed the stomachs and attached the esophagus to the small intestine. They also removed part of the brain, liver, lungs, and heart, then sewed the prisoner back up. The lucky prisoners died. The unlucky ones survived and were subjected to further experiments.

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An old photograph of vivisection performed without Anesthesia

Germ Warfare

Japanese scientists also infected prisoners with communicable diseases to study how to make germ warfare effectively. The guards at 731 would often drop plague fleas in bombs on the prisoners. The Japanese decided to take their experiments outside the facility. Tularemia was released on Chinese civilians outside the facility, and Japanese planes dropped plague infested fleas on Ningbo and Changde. Thousands of people died because of this.

Frostbite testing

Physiologist Hisato performed experiments by freezing various appendages of prisoners solid. He would then strike the limb with a stick to hear the noise. After this, he would then rethaw the limb. To test if any areas were still frozen, the prisoner would be bludgeoned.


Doctors would often force prisoners to have sex with infected prisoners to study transmission of the disease. Furthermore, prisoners would be vivisected at various stages of infection to study how the disease progressed. Children were also infected with syphilis by the doctors.

Rape/forced pregnancy

Female prisoners were often raped and forcibly impregnated for experiments. The scientists were attempting to investigate the transmission of disease from mother to child. Specific objects tested were fetal survival outside the womb, and how much genital damage the women could survive. The guards would call the women’s genitals “bean jam buns” because of the damage.

A person who was a member of the unit tells the story: ““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.”” (from the book Unit 731 Testimony by Hal Gold)

Weapon testing:

Japanese soldiers tested grenades, bayonets, flamethrowers, germ bombs, chemical weapons, bullets, and explosive bombs on live prisoners.

The unit was supported by Japanese universities and medical schools which supplied doctors and research staff. No prisoner came out alive of the Unit’s gates.
Unit 731 and an affiliated site, known as Unit 1644, continuously bred plague infected fleas while another satellite complex, Unit 8604, was used to breed rats. Outside of the facility, plague fleas, infected clothing, and infected supplies were packaged into bombs and dropped on various targets throughout China.

They were known to have spread plague infected fleas over the coastal city of Ningbo in 1940 and Hunan’s Changde City in 1941 using low-flying planes. On September 22nd 1945, the Imperial Japanese Army had prepared and scheduled to drop one of these patented plague bombs on San Diego, California. However, they surrendered five weeks before the bomb was due to launch.

When Russians finally invaded the Harbin area in 1945, the researchers in Unit 731 abandoned their work and fled to Japan. General Ishii ordered them to take their secret to the grave and issued all of them with vials of potassium cyanide in the event that they were captured. Japanese troops were sent to blow up the compound and destroy all of the evidence, but it was so well built that it survived somewhat intact.

After continuing pressure from the American military, a microbiologist known as Lieutenant Colonel Murray Sanders was provided with a manuscript by the Japanese government detailing their involvement in biological warfare. He took it directly to the then Supreme Commander of the Allied Forces; Douglas MacArthur. Yet, when evidence of the unit was finally discovered, rather than punish the perpetrators, the Americans decided to grant the researchers immunity in exchange for their data on biological and chemical warfare.

On the 6th of May 1947, MacArthur wrote to the Pentagon stating that “possibly some statements from Ishii probably can be obtained by informing Japanese involved that information will be retained in intelligence channels and will not be employed as ‘War Crimes’ evidence”. They managed to dismiss victims’ testimonies as “Communist Propaganda”.

The physicians provided the U.S. government with details of their research, agreed to withhold this evidence from other Allied countries, and in exchange were granted immunity. One member of Unit 1644, Masami Kitaoka, went on to perform experiments on unwilling Japanese subjects. He infected prisoners with rickettsia and mental health patients with typhus while working for Japan’s National Institute of Health Sciences.

That’s all bad, but you know what the worst part is? Japan has never actually apologized for Unit 731.