Introduction
You want to uncover the hidden truth behind imperial Japan's most notorious wartime atrocities. Official secrecy and decades of institutional denial have obscured the full scale of human experimentation carried out in occupied China. Hal Gold exposes the harrowing history of imperial Japan's covert biological warfare and human experimentation unit through survivor testimonies and archival records. You will discover how a vast network of medical professionals transformed prisoners into subjects for fatal research.
The book traces this dark history across five core areas.
- How did military ambition create an offensive biological warfare program?
- What horrors occurred inside secret facilities like Pingfang?
- How did researchers weaponize deadly pathogens against civilians?
- Why did American authorities grant immunity to the perpetrators?
- How did former staff members build successful postwar careers in silence?
1. Historical Background and Origins
Japan revolutionized military medicine during the Russo-Japanese War by prioritizing preventive sanitation over reactive treatment, drastically reducing disease-related deaths. While other nations historically lost vastly more soldiers to the silent enemy of disease than to bullets, Japan implemented rigorous sanitation, water testing kits, and bacteriological laboratories in every field hospital, achieving an unprecedented low disease mortality rate.
Japan built its offensive biological warfare infrastructure upon early medical sanitation successes and the personal ambitions of Ishii Shiro.
U.S. Army doctor Louis Livingston Seaman accompanied Japanese troops in Manchuria and documented that only 1.2 percent of the entire army died of sickness or disease. This success contrasted with traditional conflicts where 80 percent of total mortality was caused by the silent enemy. Japan also took 60,000 Russian prisoners after the battle of Mukden.
The Japanese army successfully enforced the mandatory consumption of prophylactic creosote pills by framing them as an imperial command. When soldiers resisted taking bad-tasting pills issued to prevent bacterial infections, officers achieved compliance through direct authority.
- Issue prophylactic pills to soldiers with instructions to take one after each meal.
- Mark the containers as the direct will of the emperor to guarantee compliance.
Ishii Shiro and the Manchurian Incident
Ishii Shiro leveraged his academic pedigree at Kyoto Imperial University and high-level social connections to spearhead Japan's offensive biological warfare research. Born on June 25, 1892, Ishii possessed a driven personality, married the university president's daughter, and capitalized on the 1925 Geneva Convention to lobby military leaders. He reasoned that if biological weapons were outlawed, they must be exceptionally potent. Ishii spent over two years visiting more than twenty European countries, the United States, and Canada on a self-funded tour to research gas and bacteriological developments.
The Japanese military engineered the Manchurian Incident as a false-flag pretext to occupy Manchuria and secure a captive population for human experimentation. Terry's Guide to the Japanese Empire and South Manchuria Railway pamphlets documented the rapid modernization and transport efficiency of the region prior to the takeover.
At 10:30 P.M. on September 18, 1931, the Manchurian Incident started when an explosion occurred near Mukden. The Japanese blamed Chinese regular soldiers and took three months to completely occupy Manchuria, establishing the puppet state of Manzhouguo.
The kenpeitai military police acted as the primary procurement arm for Unit 731, capturing resistance members and suspected spies to be fed into the human experimentation program. Selected for unyielding personalities, kenpeitai officers interrogated detainees using intense psychological intimidation and torture, classifying them as Special Handling forces destined never to return. Former kenpeitai officer Miou Yutaka described how prisoners were bound with ropes, placed in closed freight cars on the South Manchuria Railway, and met at the station by black windowless trucks from Unit 731.
Decades of governmental concealment and a strict code of silence enforced by General Ishii Shiro kept Unit 731 hidden until public exhibitions and survivor testimonies broke the silence. Four decades following the end of World War II, details began surfacing as aging perpetrators came forward. An estimated three thousand individuals were killed at the hands of Unit 731 before the end of the war, originating from Manchuria, China, Russia, Korea, Europe, and America.
2. Facilities and Human Experimentation
The Japanese military established massive secret fortresses like Zhongma and Pingfang to conduct systematic human vivisections and germ tests.
Ishii established his first secret human experimentation facility, known as Zhongma Fortress, near Beiyinhe after forcibly evicting local residents. A poor neighborhood of about 300 homes was burned down, and an area of 500 square meters was designated a restricted military zone to build the fortress with hundreds of rooms in less than a year.
The complex was built by forced Chinese laborers who were executed upon completion to preserve secrecy. It featured a high wall, electric wire, and was heavily guarded while housing hundreds of prisoners subjected to lethal medical experiments.
The complex held 30 cells containing 500 to 600 prisoners at any given time, with a maximum capacity of 1,000 and a 1-month maximum life expectancy for prisoners.
A daring prisoner-led escape from Zhongma Fortress in 1936 exposed the existence of the secret facility, forcing the Japanese to relocate. Prisoner Li and about 40 inmates attempted to escape; around 20 made it outside, and some were sheltered by local villagers before escaping to join resistance fighters.
From Zhongma to Pingfang
Following the Zhongma escape, the Japanese built a much larger, highly fortified headquarters at Pingfang that operated as a sprawling industrial-scale germ warfare installation. The Pingfang compound covered a 6-square-kilometer tract of land and contained 70 buildings.
Local residents were told the massive facility was a lumber mill, which led researchers to privately refer to the human test subjects as logs. The compound included specialized prison blocks, laboratories, incinerators, and a dedicated airfield for specimen transport.
Vivisection and Satellite Units
Unit 731 systematically subjected live human subjects to controlled infections, extreme blood drainage, and unanesthetized vivisections to gather pathological data. Researchers performed vivisections on living prisoners to examine organs before putrefactive bacteria could alter the tissues, recording the progression of diseases and collecting biological samples.
Former unit member Ueda Yataro described eagerly drawing a 10-cubic-centimeter blood sample from a dying prisoner in cell block Number 7 while ignoring the man's agony. Prisoners could endure up to 500 cubic centimeters of blood drawn at two- to three-day intervals before death.
The operation relied heavily on civilian academic institutions, with university researchers rotating through Pingfang and pathological specimens being flown regularly to Tokyo. Amano Ryuji, a procurement worker, witnessed large numbers of human body parts and preserved specimens arriving at the Tokyo lab from Manchuria. Decades later, bones were dug up in Shinjuku near the former Army Medical College.
Unit 731 operated an extensive network of satellite facilities across Asia, including units in Anda, Xinjing, Guangzhou, Beijing, and Singapore. These sibling units held 20,000 total personnel across units and specialized in various aspects of biological and chemical warfare.
- Anda hosted open-air bomb testing.
- Unit 100 in Xinjing conducted animal pathogen research.
- Nami Unit 8604 in Guangzhou and Unit 1855 in Beijing handled regional operations.
- The 1,000-member Singapore facility produced flea-breeding plague under Operation Oka 9420.
Former Singapore lab worker Othman Wok recalled pulling fleas from chloroform-anesthetized rats using pincers as part of Operation Oka 9420. The Ishii organization conducted its first battlefield biological warfare test during the Nomonhan Incident in 1939 by dumping typhoid bacteria into a river.
Three former Youth Corps members testified decades later about carrying 22 or 23 eighteen-liter oil drums across swampy ground at night to dump the bacteria. Facing imminent defeat in a border clash with Soviet-Mongolian forces, unit members transported the oil drums filled with typhoid pathogens cultured in vegetable gelatin and poured them into the river upstream.
3. Pathogens and Field Testing
Unit 731 mass-produced disease vectors such as fleas, rats, and ceramic bombs to wage biological warfare against civilian populations.
Rodents, Fleas, and Disease Deployment
Unit 731 relied on local civilian populations, including schoolchildren and farming families, to cultivate rats on a massive scale for disease dissemination. In Saitama Prefecture, high school students on a bicycling research project interviewed farming families who recalled raising rats in wood-framed cages as a source of income during the war. On February 26, 1995, the Asahi Broadcasting Company presented a documentary titled The Mystery of the Rats That Went to the Continent.
Rats were harvested from Manchuria and given to farming families to raise in simple cages, holding six rats per cage as a capacity. The animals were collected at a research center in Saitama Prefecture and transported via Tokyo to the continent. After the war, the U.S. Army continued this infrastructure through Unit 406.
Flea production was managed by employing elderly prisoners who were subjected to strict confinement rules to harvest parasites from padded clothing. About ten prisoners over fifty years old were housed in a shed at Pingfang and told they did not have to work except to produce one hundred large fleas a day. They wore heavily padded clothing day and night, from which Japanese workers in white coveralls collected mature fleas. Han Xiao's book Crimes of Unit 731 describes how the ten elderly prisoners were given specific rules and had their clothes turned inside out to harvest fleas into aluminum boxes.
You can trace the specific rules imposed on these prisoners:
- Do not come into contact with other prisoners
- Never talk about this work to anyone
- Always sleep with your clothes on
- Do the required work every day
The Suzuki Group construction company built a new wing at Pingfang in 1940 to support this work. The group generated eight hundred to one thousand a day in total fleas collected from the ten prisoners.
Cholera was researched by infecting human prisoners and subsequently using domestic animals as carriers to spread the disease into local population centers. Unit members infected human prisoners with germs, then spread the illness to local populations by using dogs fed with cholera-laced pork. Former army captain Kojima Takeo testified about a cholera campaign where dogs were used to spread the disease in a village eight kilometers west of Chinan, causing severe symptoms and high mortality. Twenty percent of those who contracted the illness died.
Research on Epidemic Hemorrhagic Fever used human subjects disguised under the code word "monkeys" in published medical literature. After discovering that EHF was carried by ticks, researchers ground two hundred ticks into a saline solution and tested it on subjects. Published reports disguised human subjects as monkeys, a transparent sham recognized by the medical community.
General Kitano presented findings on EHF at a Tokyo University parasitology convention in 1943, publishing research papers in journals like the Nihon Byori Gakkaishi. An Asahi newspaper story on April 2, 1943 celebrated the conquest of the strange sickness. The disease carried a death rate of fifteen to twenty percent. The Imperial Army clearly identified the disease in 1938, and Japanese and Soviet researchers found the agent was a virus in 1941. Test subjects recorded a body temperature of 40.2 degrees Celsius that proved they were humans rather than monkeys.
Plague was deployed as a rapid-action biological weapon through aerial dissemination over Chinese population centers, causing mass casualties. Because plague kills within three days, it was prioritized by Ishii's researchers. Joint operations by Unit 731 and Unit 1644 dropped plague-infected materials mixed with wheat and corn from aircraft, resulting in severe outbreaks that were subsequently sealed off. Qian Guifa and other survivors from Ningbo and surrounding villages witnessed aerial drops of smoky material that led to fatal outbreaks among their families and local residents.
The plague attack against the Kaimingjie area of Ningbo occurred in October 1940. One hundred persons died within a few days after the Ningbo attack. Ishii commanded another plague attack in September 1942 that killed three hundred eighty people. A maximum of twenty people died in a single day during the 1942 attack, while Chinese disease prevention specialists recorded ninety-seven people of total deaths.
To overcome the limitation of explosives killing insects and to enable high-altitude delivery, Unit 731 developed specialized ceramic biological bombs. Standard explosives detonated with too much force for biological agents, so Ishii utilized traditional Japanese pottery makers to manufacture ceramic bombs based on historical precedents like poison gas production at Okunoshima and ceramic land mines. Artisans in Kyoto pottery regions produced sixty-five-centimeter ceramic bombs with screw-tops in the nose according to Ishii's precise specifications without knowing their true purpose.
Frostbite and Weaponized Plagues
Dr. Yoshimura Hisato conducted deliberate and destructive frostbite experiments on human subjects to prepare the Japanese military for cold-weather combat against the Soviet Union. Physiologist Yoshimura induced extreme frostbite by exposing bared, water-soaked limbs to sub-zero outdoor temperatures and industrial refrigerators, striking them with clubs to check if they were frozen through before testing treatments. Nishi Toshihide testified at the Khabarovsk trials about the frostbite experiments, and former members confirmed seeing victims with missing hands and feet.
Japan had crushed Russia's forces in 1905. Outdoor winter temperatures in Manchuria dropped to minus twenty to thirty degrees Celsius, while Yoshimura's refrigerator laboratory at Pingfang reached minus seventy degrees Celsius. Researchers discovered thirty-seven degrees to forty degrees Celsius as the optimal warm water temperature for thawing frostbitten limbs. Yoshimura tested five hundred males as subjects in his ethnic cold-adaptability research published in the Japan Journal of Physiology between 1950 and 1952, and he published his book of reminiscences in 1984.
4. Late-War Plans and Postwar Immunity
As defeat loomed, Japan plotted desperate suicide attacks while American occupation authorities traded war crimes immunity for exclusive research data.
Operation PX and Okinawa
Japanese military planners conceived Operation PX as a desperate joint army-navy suicide mission to attack the American mainland with biological weapons using submarine-launched aircraft. The plan involved using long-range submarines known as underwater aircraft carriers, specifically the I-400 class, to approach the U.S. West Coast and launch seaplanes to disperse plague, cholera, and other pathogens. The top naval leaders and Ishii developed the plan, but it was abruptly canceled on March 26, 1945, by General Umezu Yoshijiro, who feared it would escalate into an endless war against bacteria and draw global derision.
Former captain Eno Yoshio revealed details of Operation PX in a Sankei newspaper interview on August 14, 1977, noting that the I-400 submarine had a displacement of 3,530 tons and a range of 31,000 nautical miles.
The Japanese military planned to deploy plague bacteria against American invasion forces in Okinawa, viewing the island as expendable. As American forces approached Okinawa, the Ishii organization prepared plague bacteria to repel the invaders. Ito Kageaki, a former member of Unit 1855 in Beijing who was assigned to raise fleas for plague propagation, testified that the military considered Okinawa expendable due to racial disdain for Okinawans as part of the former Kingdom of the Ryukyus, unlike Japan proper.
Ito Kageaki gave testimony in the Okinawa Times in January 1994 during the Unit 731 Exhibition, describing how his unit expanded around 1944 to bring in plague germs and experiment on Chinese prisoners.
American Bargaining and Soviet Trials
General Douglas MacArthur granted immunity from war crimes prosecution to Unit 731 leaders in exchange for exclusive access to their biological warfare research data. When Lieutenant Colonel Murray Sanders arrived in Yokohama aboard the Sturgess in September 1945 to investigate Japanese biological warfare, Dr. Naito Ryoichi acted as an information filter. Faced with Japanese fears of the Soviet legal system, American authorities offered immunity from war crimes trials so that the U.S. could secure exclusive ownership of the human experimentation data, keeping it out of Soviet hands.
Naito Ryoichi approached Lieutenant Colonel Murray Sanders upon his arrival at Yokohama port, eventually providing a comprehensive manuscript detailing Japanese biological warfare command structures after Sanders threatened to bring in the Communists.
Recognizing that American occupation authorities sought practical intelligence rather than retributive justice, Ishii offered to describe his program in detail in exchange for written immunity for himself, his superiors, and his subordinates. Ishii argued that his decades of research, particularly regarding the viability of bacteria in specific Asian climates and cold regions, would be a distinct advantage to the United States in the event of a future war with the Soviet Union.
As the war ended, Unit 731 facilities in Manchuria and China were systematically destroyed, and staff members were sworn to absolute secrecy. Recognizing the impending Soviet advance into Manchuria, the Japanese blew up the facilities of Unit 731 and its branch units to erase evidence of human experimentation. Staff members evacuated via special trains through Korea and Japan, while Shiro Ishii instructed his subordinates to take jobs away from public offices, avoid contacting one another, and carry the secret to their graves.
At the Pingfang fortress, massive double stacks of the boiler room remained as a monument, while installations like Unit 1644 in Nanjing had prison cells and dissection rooms that were later repurposed as hospitals.
The Soviet Union pursued its own prosecution of former Unit 731 members, staging the Khabarovsk trial after being denied full access by the United States. While the United States traded immunity for research data to maintain an intelligence monopoly, the Soviet Union demanded access to interrogate Ishii and his officers over experiments that killed thousands of Chinese and Manchurians. After the U.S. restricted their access, the Soviets conducted their own war crimes trial in Khabarovsk in December 1949, where twelve former unit members confessed that biological warfare units had been established under direct orders from Emperor Hirohito.
5. Postwar Events and Institutional Cover-Up
Former unit members integrated into elite peacetime careers and business ventures while the government enforced decades of strict historical denial.
Criminal Connections and Business Ventures
High-ranking members of Unit 731 secured elite positions in Japanese academia, science, and industry. Kitano Masaji became a cofounder of Green Cross and served on the Special Committee for Antarctic Research. Okamoto Kozo became the dean of the Faculty of Medicine at Kyoto University. Ishii Shiro died of throat cancer in 1959 at age sixty-nine.
Leveraging financial opportunities presented by the Korean War, former unit figures Naito Ryoichi, Kitano Masaji, and Futagi Hideo founded Japan's first blood bank in 1951, later named Green Cross. In February 1988, U.S. medical researchers identified 18 patients in Japan infected with the AIDS virus via Green Cross blood products. Two of the infected patients brought suit against the company in May 1988.
North Korea and China lodged formal protests claiming American forces scattered bacteria-carrying insects and smallpox during the Korean War. A total of 2,600 cases of epidemic hemorrhagic fever were reported among U.S. troops during three years of the conflict, and 165 people died. The names of 10 former Unit 731 members appeared in U.S. Army medical reports regarding the disease.
In January 1948 at a branch of Teikoku Bank in Tokyo, a criminal killed 12 employees by administering poison under the guise of a preventive medicine distribution. The murderer took 181,850 yen from the bank desks. Four survivors recovered to bear witness and help create Japan's first montage photo. Hirasawa died in jail in 1987 at age ninety-five.
Uncovered Remains and Historical Suppression
Information regarding Unit 731 was heavily suppressed, rarely passed down by former members, and tightly guarded by government bodies to avoid public scandal and compensation claims. As recently as June 26, 1995, the Japan Times reported that a woman in Sendai discovered a résumé showing her late father worked for the secret germ warfare research army. This reflected half a century of the Japanese government's consistent denial of human experiments and biological warfare.
In June 1989, human bones were unearthed at a construction excavation site for a new facility of the Ministry of Health and Welfare in Shinjuku Ward. On April 22, 1992, Dr. Sakura Hajime announced his identification findings regarding more than one hundred people whose unburied bones showed a 3 to 1 ratio of males to females.
A former kenpeitai member named Iwasaki testified to using a water torture device for six years in Harbin before sending unyielding prisoners to Unit 731 for human experiments. You can see how the system operated by reviewing the physical steps of this interrogation method:
- pour water on the victim's chest to prevent a heart attack;
- place a cloth over the mouth and nose;
- trickle water over the cloth slowly until the belly swells within five or six minutes.
10 Key Ideas
- Japan built its offensive biological warfare infrastructure upon early medical sanitation successes and the personal ambitions of Ishii Shiro.
- The Japanese military established massive secret fortresses like Zhongma and Pingfang to conduct systematic human vivisections and germ tests.
- Unit 731 mass-produced disease vectors such as fleas, rats, and ceramic bombs to wage biological warfare against civilian populations.
- Physiologist Yoshimura induced extreme frostbite by exposing bared, water-soaked limbs to sub-zero outdoor temperatures and industrial refrigerators, striking them with clubs to check if they were frozen through before testing treatments.
- Japanese military planners conceived Operation PX as a desperate joint army-navy suicide mission to attack the American mainland with biological weapons using submarine-launched aircraft.
- Ito Kageaki gave testimony in the Okinawa Times in January 1994 during the Unit 731 Exhibition, describing how his unit expanded around 1944 to bring in plague germs and experiment on Chinese prisoners.
- General Douglas MacArthur granted immunity from war crimes prosecution to Unit 731 leaders in exchange for exclusive access to their biological warfare research data.
- As the war ended, Unit 731 facilities in Manchuria and China were systematically destroyed, and staff members were sworn to absolute secrecy.
- High-ranking members of Unit 731 secured elite positions in Japanese academia, science, and industry.
- Information regarding Unit 731 was heavily suppressed, rarely passed down by former members, and tightly guarded by government bodies to avoid public scandal and compensation claims.