Unit 731
In 1936, the Empire of Japan established a secret research facility in the Pingfang district of Harbin, Manchukuo. This location became known as Unit 731 under the command of Lieutenant General Shirō Ishii. The unit operated within the Japanese puppet state until 1945, maintaining multiple branches across mainland China and Southeast Asia. The facility was designed to conduct large-scale biological and chemical warfare research alongside lethal human experimentation. It received strong support from high-ranking military officials including Colonel Chikahiko Koizumi, who later served as Japan's Health Minister. By 1939, the organization had expanded to include over 3,000 staff members and 150 structures. The complex could detain up to 600 prisoners concurrently for experimental purposes. Prisoners were often referred to as logs by the staff, a dehumanizing term derived from the facility's cover story as a lumber mill. Most victims were Chinese civilians, but many were also Russian, Korean, or other nationalities. No documented survivors exist from the experiments conducted inside the facility itself.
Thousands of men, women, children, and infants interned at prisoner camps underwent vivisection without anesthesia. These procedures were usually lethal and involved removing organs to study disease effects on the human body. Limbs were amputated to study blood loss, sometimes reattached to opposite sides of victims' bodies. Researchers performed invasive surgeries such as stomach removal with esophagus reattachment to intestines. Brain, lung, and liver parts were extracted from living subjects for pathological analysis. A junior uniformed employee recalled seeing jars holding preserved human heads and hands in formalin solutions. One jar contained a pregnant woman's body with an exposed fetus showing hair growth. Testimony from former member Okawa Fukumatsu confirmed he had vivisected thousands of people during his tenure. Military police and Special Services Agency officers found victims while physicians maintained their health before dispatching them for experimentation. Some prisoners were deliberately infected with plague bacteria and other microbes to observe progression. Those who did not die from infection were murdered using potassium cyanide or chloroform. The New York Times interviewed a former medical assistant who described cutting open a live human being who screamed terribly until death. Staff stuffed rags into mouths to stifle screaming during these procedures.
By 1939, Shirō Ishii condensed laboratory discoveries into six potent pathogens including anthrax, typhoid, paratyphoid, glanders, dysentery, and plague-infected fleas. These agents were robust enough to ignite epidemics of considerable magnitude and resilient to aerial dispersal. Field trials involved military expeditions on unsuspecting civilians aiming to devise efficient dissemination methods. Unit 731 developed biodegradable bombs housing live rats and fleas infected with diseases designed to explode mid-air. Low-flying aircraft spread plague-infected fleas over Chinese cities including coastal Ningbo and Changde in 1940 and 1941. These operations killed tens of thousands with bubonic plague epidemics. An expedition to Nanjing involved spreading typhoid and paratyphoid germs into wells, marshes, and houses. Infected snacks distributed to locals caused outbreaks shortly after distribution. At least twelve large-scale bioweapon field trials occurred between 1940 and 1943. Eleven Chinese cities were attacked with biological agents resulting in an estimated 400,000 civilian deaths from cholera, anthrax, and plague. Plague-infected animals released near the end of war caused outbreaks killing at least 30,000 people in Harbin area from 1946 to 1948. Japanese researchers produced substantial quantities monthly: 300 kg of plague, 500, 700 kg of anthrax, 800, 900 kg of typhoid, and 1,000 kg of cholera. Unit 100 also deployed aerial spraying methods similar to those examined by Unit 731.
Lieutenant Colonel Murray Sanders arrived in Yokohama aboard the American ship Sturgess in September 1945 to investigate Japanese biological warfare activity. He had no initial knowledge of what Unit 731 was until threatening to bring Soviets into the picture. The morning after his threat, Sanders received a manuscript describing Japan's involvement in biological warfare. General Douglas MacArthur struck a deal granting immunity to physicians including their leader Shirō Ishii. This agreement provided exclusive American access to research data from human experimentation in exchange for secrecy. American occupation authorities monitored activities of former unit members including reading and censoring their mail. The Tokyo War Crimes Tribunal heard only one reference to poisonous serums on Chinese civilians in August 1946. Joseph R Massey instigated the claim but it was dismissed by tribunal president Sir William Webb for lack of evidence. Judge Röling later expressed bitterness about being informed that centrally ordered Japanese war criminality was kept secret from the court. While German physicians faced trial and publicized crimes, U.S. concealed information about Japanese experiments securing immunity for perpetrators. Critics argued racism led to double standards as perpetrators were exempt while U.S. held tribunals in 1948 indicting nine physician professors conducting vivisection upon captured American pilots. Two professors received death sentences while others got fifteen to twenty years imprisonment.
Twelve top military leaders and scientists from Unit 731 and affiliated prisons faced prosecution during Khabarovsk war crimes trials in December 1949. Among those accused was General Otozō Yamada, commander-in-chief of the million-man Kwantung Army occupying Manchuria. Lead prosecuting attorney Lev Smirnov had been a top Soviet prosecutor at Nuremberg Trials. Sentences ranged from two to twenty-five years in Siberian labor camps. All defendants returned to Japan by 1956 despite unusually lenient sentences by Soviet standards. The United States refused to acknowledge trials branding them communist propaganda. US also asserted trials served as distraction from Soviet treatment of several hundred thousand Japanese prisoners. USSR claimed US gave diplomatic leniency in exchange for human experimentation information. Former members likely passed biological experimentation data to Soviet government for judicial leniency. Soviet Union built a biological weapons facility in Sverdlovsk using documentation captured from Unit 731 in Manchuria. A partial transcript published in different languages included English editions released by Moscow foreign languages press. The trial proceedings documented accusations of germ warfare manufacturing and employment against Chinese civilians.
In August 2002, Tokyo District Court formally acknowledged that Japan conducted biological warfare in China holding state responsible for related deaths. Presiding judge Koji Iwata ruled Unit 731 used bacteriological weapons on Chinese civilians between 1940 and 1942. Victims' compensation claims were rejected based on international peace treaties settling matters already. In April 2018, National Archives of Japan released names of 3,607 personnel affiliated with Unit 731. Professor Katsuo Nishiyama announced intent to publish list online promoting further research. Japanese history textbooks usually contain references but do not provide specific details about activities conducted at facility. Ministry for Education attempted removing passages describing experiments before Supreme Court ruled in 1997 requiring inclusion as legal violation of freedom of speech. Prime Minister Junichiro Koizumi responded to House inquiry stating government lacked records recognizing gravity of matter. Office of Special Investigations created watchlist banning suspected Axis collaborators from entering United States. Fewer than one hundred Japanese participants identified despite over sixty thousand names added due to document microfilming decisions. Department of Defense decided not to microfilm vast collection before returning to Japanese government. Information needed to identify individuals became impossible to recover cumulatively. International lawyer Kōnen Tsuchiya filed class action suit demanding reparations using evidence filed by Professor Makoto Ueda finding all levels baseless.
Up Next
Continue Browsing
Common questions
When was Unit 731 established and where did it operate?
The Empire of Japan established Unit 731 in 1936 within the Pingfang district of Harbin, Manchukuo. The facility operated until 1945 while maintaining multiple branches across mainland China and Southeast Asia.
Who commanded Unit 731 and how many staff members worked there by 1939?
Lieutenant General Shirō Ishii commanded Unit 731 from its inception in 1936. By 1939 the organization had expanded to include over 3,000 staff members and 150 structures.
What specific biological weapons did Unit 731 develop and deploy against Chinese cities?
Shirō Ishii condensed laboratory discoveries into six potent pathogens including anthrax, typhoid, paratyphoid, glanders, dysentery, and plague-infected fleas by 1939. Low-flying aircraft spread plague-infected fleas over Chinese cities including coastal Ningbo and Changde in 1940 and 1941.
Why did American authorities grant immunity to Unit 731 physicians after World War II?
General Douglas MacArthur struck a deal granting immunity to physicians including their leader Shirō Ishii in September 1945. This agreement provided exclusive American access to research data from human experimentation in exchange for secrecy.
When did Tokyo District Court formally acknowledge Japan conducted biological warfare in China?
Tokyo District Court formally acknowledged that Japan conducted biological warfare in China in August 2002. Presiding judge Koji Iwata ruled Unit 731 used bacteriological weapons on Chinese civilians between 1940 and 1942.