Second Sino-Japanese War
During the Second Sino-Japanese War, Japanese forces used biological and chemical warfare against several parts of China. The Japanese were known to be willing to do just about anything to defeat the Chinese and they even created their own biological/chemical warfare laboratory. Unit 731 covered six square kilometers of Pingfang, a district of Harbin in the Japanese puppet state of Manchukuo which is now Northeast China.
Unit 731 operated from 1935 until 1945 and it is estimated that up to 250,000 men, women and children were subjected to experimentation by the laboratory. The laboratory tested out both chemical and biological agents against Chinese, Russian, South East Asians, Pacific Islanders and a small number of Allied war prisoners. The vast majority of the victims were Chinese. Some of the prisoners would be given diseases and then dissected alive in order to determine how the disease affected the body.
The Japanese used the information to experiment with germ warfare. They would place plague-ridden fleas and infected clothing and supplies in bombs and drop them on different targets. Cholera, anthrax and the bubonic plague were found to have killed as many as 400,000 civilians. Bubonic plague fleas were also spread by airplanes over coastal Chinese cities. In addition to the fleas, there was aerial spraying of the plague over cities which resulted in the deaths of thousands. The Japanese had planned a similar attack on San Diego, California in September 1945, but ended up surrendering five weeks earlier.
The Japanese were not opposed to the use of chemical attacks either. They were used up to 2,000 times in 77 different counties during the war. The chemical weapons attacks claimed the lives of tens of thousands. When the war ended, Japan abandoned much of their chemical weapons in China by burying them or dumping them in rivers. Many civilians were killed by the leaking containers and to this day not all of the canisters have been found or properly disposed of.