Unit 731 and its affiliated units (Unit 1644 and Unit 100 among others) were involved in research, development and experimental deployment of epidemic-creating biowarfare weapons in assaults against the Chinese populace (both military and civilian) throughout World War II.
Plague-infected fleas, bred in the laboratories of Unit 731 and Unit 1644, were spread by low-flying airplanes upon Chinese cities, including coastal Ningbo and Changde, Hunan Province, in 1940 and 1941.
This military aerial spraying killed tens of thousands of people with bubonic plague epidemics.
An expedition to Nanking involved spreading typhoid and paratyphoid germs into the wells, marshes, and houses of the city, as well as infusing them into snacks to be distributed among the locals.
Epidemics broke out shortly after, to the elation of many researchers, where it was concluded that paratyphoid fever was "the most effective" of the pathogens.

At least 12 large-scale field trials of biological weapons were performed, and at least 11 Chinese cities were attacked with biological agents.
An attack on Changda in 1941 reportedly led to approximately 10,000 biological casualties and 1700 deaths among ill-prepared Japanese troops, with most cases due to cholera.
Japanese researchers performed tests on prisoners with bubonic plague, cholera, smallpox, botulism, as well as other diseases.
This research led to the development of the defoliation bacilli bomb and the flea bomb used to spread bubonic plague.
Some of these bombs were designed with porcelain shells, an idea proposed by Ishii in 1938.

These bombs enabled Japanese soldiers to launch biological attacks, infecting agriculture, reservoirs, wells, as well as other areas with anthrax, plague-carrier fleas, typhoid, dysentery, cholera or other deadly pathogens.
During biological bomb experiments, researchers 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 to unsuspecting victims.

During the final months of World War II, Japan planned to use plague as a biological weapon against San Diego, California.
The plan was scheduled to launch on September 22, 1945, but Japan surrendered five weeks earlier.
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 at least 400,000 Chinese civilians.
Tularemia was tested on Chinese civilians.

Due to pressure from numerous accounts of the bio-warfare attacks, Chiang Kai-shek sent a delegation of army and foreign medical personnel in November 1941 to document evidence and treat the afflicted.
A report on the Japanese use of plague-infested fleas on Changde was made widely available the following year, but was not addressed by the Allied Powers until Franklin D. Roosevelt issued a public warning in 1943 condemning the attacks.
Unit 731 and its affiliated units (Unit 1644 and Unit 100 among others) were involved in research, development and experimental deployment of epidemic-creating biowarfare weapons in assaults against the Chinese populace (both military and civilian) throughout World War II. Plague-infected fleas, bred in the laboratories of Unit 731 and Unit 1644, were spread by low-flying airplanes upon Chinese cities, including coastal Ningbo and Changde, Hunan Province, in 1940 and 1941. This military aerial spraying killed tens of thousands of people with bubonic plague epidemics. An expedition to Nanking involved spreading typhoid and paratyphoid germs into the wells, marshes, and houses of the city, as well as infusing them into snacks to be distributed among the locals. Epidemics broke out shortly after, to the elation of many researchers, where it was concluded that paratyphoid fever was "the most effective" of the pathogens.
At least 12 large-scale field trials of biological weapons were performed, and at least 11 Chinese cities were attacked with biological agents. An attack on Changda in 1941 reportedly led to approximately 10,000 biological casualties and 1700 deaths among ill-prepared Japanese troops, with most cases due to cholera. Japanese researchers performed tests on prisoners with bubonic plague, cholera, smallpox, botulism, as well as other diseases. This research led to the development of the defoliation bacilli bomb and the flea bomb used to spread bubonic plague. Some of these bombs were designed with porcelain shells, an idea proposed by Ishii in 1938.
These bombs enabled Japanese soldiers to launch biological attacks, infecting agriculture, reservoirs, wells, as well as other areas with anthrax, plague-carrier fleas, typhoid, dysentery, cholera or other deadly pathogens. During biological bomb experiments, researchers 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 to unsuspecting victims.
During the final months of World War II, Japan planned to use plague as a biological weapon against San Diego, California. The plan was scheduled to launch on September 22, 1945, but Japan surrendered five weeks earlier. 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 at least 400,000 Chinese civilians. Tularemia was tested on Chinese civilians.
Due to pressure from numerous accounts of the bio-warfare attacks, Chiang Kai-shek sent a delegation of army and foreign medical personnel in November 1941 to document evidence and treat the afflicted. A report on the Japanese use of plague-infested fleas on Changde was made widely available the following year, but was not addressed by the Allied Powers until Franklin D. Roosevelt issued a public warning in 1943 condemning the attacks.
Unit 731