According to historians Yoshiaki Yoshimi and Seiya Matsuno , the chemical weapons were authorized by specific orders given by Japanese Emperor Hirohito himself , transmitted by the Imperial General Headquarters . For example , the Emperor authorized the use of toxic gas on 375 separate occasions during the Battle of Wuhan from August to October 1938 . They were also used during the invasion of Changde . Those orders were transmitted either by Prince Kan ' in Kotohito or General Hajime Sugiyama . Gases manufactured in Okunoshima were used more than 2,000 times against Chinese soldiers and civilians in the war in China in the 1930 's and 1940 's Bacteriological weapons provided by Shirō Ishii 's units were also profusely used . For example , in 1940 , the Imperial Japanese Army Air Force bombed Ningbo with fleas carrying the bubonic plague . During the Khabarovsk War Crime Trials the accused , such as Major General Kiyashi Kawashima , testified that , in 1941 , some 40 members of Unit 731 air-dropped plague-contaminated fleas on Changde . These attacks caused epidemic plague outbreaks . In the Zhejiang-Jiangxi Campaign , of the 10,000 Japanese soldiers who fell ill with the disease , about 1,700 Japanese troops died when the biological weapons rebounded on their own forces
units
Unit 731
Second Sino-Japanese War