From approximately 1930 to 1945, Japan engaged in a series of military actions against China known as the Sino-Japanese war. After December 1941, China became an ally of the United States and Britain, and the fighting in China technically became part of World War II. However, the character of the fighting in China differed in some respects from that elsewhere in the Pacific: there was much deliberate cruelty against civilians, and the Japanese conducted chemical and biological warfare.
The Japanese conquest of China was often horrifically cruel and destructive, even when using only “conventional” weapons. During a 6-week period in Nanjing in 1937, for example, the Japanese army killed several hundred thousand civilians and Chinese prisoners of war and raped tens of thousands of Chinese women. Urban areas were subject to aerial bombardment with incendiaries.
Japan had adopted an expansionist policy in China following the first Sino-Japanese war in 1895, which led to the colonization of Formosa (Taiwan). The Russo-Japanese War of 1905 further extended Japanese influence into areas of northeastern China (Manchuria) and led to the annexation of Korea. In a series of fabricated “incidents,” Japanese military forces extended overt Japanese rule throughout Manchuria in 1933, and after 1937 throughout much of coastal China.
Japan did not ratify the 1925 Geneva Protocol that outlawed biological warfare (BW) and chemical warfare (CW). In 1930, Japanese military forces used an irritating agent chloroacetophenone (CN) during its suppression of a Formosa-based indigenous rebellion. Especially after 1933, Japan pursued the development of both CW and BW. In hundreds of separate incidents from 1937–1943, the Japanese military forces fighting in China used chemical weapons of the types developed in World War I. These included mustard, lewisite (often in mixtures), and another irritating substance, diphenylcyanoarsine. Chinese military forces lacked gas masks, and so they typically fled when gas was used. Although the United States later assisted in some areas to provide a defensive and offensive capability in CW, for the most part the Chinese lacked an effective chemical arsenal. Thus, the Japanese were able to use CW without having to endure retaliation in kind.
After China became a U.S. ally after the Japanese attack on Pearl Harbor (December 1941), President Roosevelt issued a warning in 1942 to the Japanese that further use of CW against China would be considered a use against the United States and that the U.S. military might retaliate in kind. Fearing the large chemical arsenal held by the Americans, Japan began to limit its use of chemical weapons against the Chinese after U.S. entry into the war in the Pacific.
As Japan faced an onslaught of both Allied and Soviet forces bent on liberating China, Japanese military forces buried up to 1 million or more chemical munitions, mostly along the Sino-Soviet border, in anticipation of warfare with the Soviet Red Army. As a result, the ongoing disposal of chemical weapons abandoned by Japan in China during the 1940s remains a problem today. Pursuant to the 1993 Chemical Weapons Convention (CWC), Japan has agreed to fund, and provide destruction technologies to rid China of, these abandoned chemical weapons.
Biological Weapons Research
In a well-funded program that lasted from approximately 1932 to the Japanese surrender in 1945, Japan researched, developed, and employed biological weapons while occupying mainland China. The primary research organization was called Unit 731, ostensibly a “sanitation” unit located near Harbin, Manchuria. The leader of this program was an ambitious Japanese military officer and microbiologist, Ishii Shiro. In addition to Unit 731, there were multiple satellite BW facilities located in most major occupied Chinese cities.
The program committed horrific crimes against humanity, including deliberately lethal testing on human captives. Field trials against civilians were conducted within these biological weapons research facilities, where victims (usually prisoners of war, or others taken from local villages) were sometimes vivisected. At least 3,000 innocent victims were murdered during biological experimentation by Japanese BW scientists in China. The weapons developed included plague-infected fleas dropped from airplanes over Chinese cities; bombs containing anthrax; and various waterborne pathogens (cholera, typhoid, paratyphoid, dysentery, and glanders), some of which were released into rural Chinese water supplies. Several cities and scores of villages in Zhejiang province in the summer of 1942 were subjected to BW attack with multiple pathogens, resulting in thousands of deaths. As a consequence of Japanese BW activities, infectious disease persisted in some Chinese villages long after the war was over.
Another branch of the Japanese military BW program included a veterinary research and development organization called Unit 100 that did work in agricultural BW. Unit 100 worked on antianimal diseases such as anthrax and glanders, as well as anticrop agents. Following the U.S. warning regarding the use of CW, Japanese use of biological weapons in China became less frequent.
After the Japanese surrender, the Soviets captured some Unit 731 scientists and related personnel. A dozen of these individuals were tried and convicted of war crimes at a court held in Khabarovsk in 1949. These individuals, however, were not executed but given various jail sentences, and most of them returned to Japan by the late 1950s. Other principal Japanese scientists and staff involved in the BW activity were granted amnesty for their war crimes by the United States in exchange for their technical data of BW effects on humans. At the time, concerns regarding the Soviet Union and its possible development of biological weapons were an important factor in this controversial decision.
Although technically not part of the Sino-Japanese War, the Japanese also mounted a BW attack during a short but vicious border war at Nohoman in 1939.This attack had the aim of contaminating water supplies used by Soviet forces. This was perhaps the first tactical antipersonnel BW attack of modern times. The effect on the Soviet forces is unknown, but the attack did not prevent a rout of the Japanese forces, and apparently it caused many unintended casualties among the retreating Japanese army.
UNIT 731
Unit 731 was the first modern biological weapons unit. It was organized by Japanese troops and conducted heinous crimes in China during World War II. Unit 731 was also referred to as “General Ishii’s Unit” because it was organized by Japanese Lieutenant General Shiro Ishii, a military surgeon.
In 1930 or 1931, General Ishii proposed to the Japanese Army that pathogenic bacteria could be used as a weapon. In August 1932, the Laboratory of Preventive Medicine was set up within the College of Military Medicine. In 1933, a Unit of Preventive Medicine in the Kwantung army was set up in the city of Harbin, Manchuria. The name was eventually changed to Kwantung Army Institute of Preventive Medicine. General Ishii was given formal command of the Kwantung Army Institute of Preventive Medicine, including its 1,300 military personnel, in 1936. In the Institute, the Japanese tried to weaponize plague, cholera, anthrax, Shigella dysenteriae, typhoid fever, tularemia, botulism, brucellosis, gangrene, glanders, influenza, meningococcus, Salmonella, smallpox, tetanus, tick encephalitis, tuberculosis, and typhus. Some toxins such as puffer fish (Fugu) toxin (i.e., tetrodotoxin) were also investigated. Tsutsugamushi fever, which is caused by rickettsia, and epidemic hemorrhagic fever were also studied.
Personnel under Ishii’s command used Chinese prisoners, dissidents, and spies as human specimens to study the effects disease and biological weapons. Altogether, about 3,000 people were sacrificed to obtain firsthand knowledge of the effects of different bacteria on humans. Despite the large scale of its biological warfare research, the identity of the Institute was kept secret.
Weaponization of bacteria was not an easy task, and General Ishii’s goal was to develop a bomb that could be delivered from an airplane to cause massive outbreaks of deadly diseases. He found that the bacteria alone were not suitable for spreading disease; he thought that fleas carrying plague were the most suitable vector for a biological weapon attack. Therefore, mass breeding of disease-carrying fleas was undertaken, using rats as hosts. Eventually the Japanese developed a porcelain bomb that incorporated a minimum amount of explosive (in order to protect the viability of the insects inside) to attack targets with plague-carrying fleas. Upon impact, the bomb’s porcelain shell was to break, and fleas were to be released, eventually reaching and biting humans. One bomb of this type carried 30,000 fleas. The survival rate of fleas when the bomb exploded was perhaps as high as 80 percent. Porcelain bombs also were made for anthrax, typhoid, and dysentery.
For the anthrax bomb, Ishii used the spore form of anthrax because of its extreme stability. When the bomb exploded, shrapnel fragments were to cause wounds through which anthrax spores entered the body. Modern-day biological weapons makers prefer to develop aerosol weapons, as the inhalation route of infection typically causes more severe disease.
At the end of World War II when Soviet Union troops invaded Manchuria, the Japanese destroyed the buildings and facilities of Unit 731 and returned all its personnel to Japan before they could be captured by advancing Soviet troops. Even so, some personnel associated with Unit 731 were arrested by the Soviets. In December 1949, these persons were trotted out in a show trial, and given sentences ranging from 3 years to 25 years by the Soviet Military Court. However, most of them were sent back to Japan without serving the full terms of their prison sentences.
The U.S. Army was surprised to see the advanced stage of the Japanese biological weapons program and tried to learn from General Ishii’s group in Japan. Instead of punishing them as war criminals, the United States protected them in an effort to obtain the information generated by Unit 731’s experiments.
References
Harris, Sheldon H., Factories of Death: Japanese Biological Warfare 1932–1945 and the American Cover-Up (New York: Routledge, 1994).
Tsuneishi, Kei’ichi, “Biological Warfare Research Conducted by the Japanese Imperial Army in Japan and China,” in Erhard Geissler and Robert Haynes, eds., Prevention of a Biological and Toxin Arms Race and the Responsibility of Scientists (Berlin: Akademie Verlag, 1991), pp. 49–73.
Williams, Peter, and David Wallace, Unit 731: Japan’s Secret Biological Warfare in World War II (New York: Free, 1989).
Williams, Peter and David Wallace, The Japanese Army’s Secret of Secrets (London: Hodder & Stoughton, 1989).
