When the United States entered the war , Allied resources were pooled at the request of the British and the U.S. established a large research program and industrial complex at Fort Detrick , Maryland in 1942 under the direction of George W. Merck . The biological and chemical weapons developed during that period were tested at the Dugway Proving Grounds in Utah . Soon there were facilities for the mass production of anthrax spores , brucellosis , and botulism toxins , although the war was over before these weapons could be of much operational use . The most notorious program of the period was run by the secret Imperial Japanese Army Unit 731 during the war , based at Pingfan in Manchuria and commanded by Lieutenant General Shirō Ishii . This unit did research on BW , conducted often fatal human experiments on prisoners , and produced biological weapons for combat use . Although the Japanese effort lacked the technological sophistication of the American or British programs , it far outstripped them in its widespread application and indiscriminate brutality . Biological weapons were used against both Chinese soldiers and civilians in several military campaigns . In 1940 , the Japanese Army Air Force bombed Ningbo with ceramic bombs full of fleas carrying the bubonic plague . Many of these operations were ineffective due to inefficient delivery systems , although up to 400,000 people may have died . During the Zhejiang-Jiangxi Campaign in 1942 , around 1,700 Japanese troops died out of a total 10,000 Japanese soldiers who fell ill with disease when their own biological weapons attack rebounded on their own forces
Unit 731
Unit 731
Biological warfare