In the intense fighting around Changde, Japanese forces could not push through the heavy Chinese resistance, and decided to launch poison gas artillery shells into the city. The shells possibly contained mustard gas or lewisite. This action was undertaken by Unit 516 of the Japanese Army during the Second Sino-Japanese War. This and other units used assorted types of chemicals in liquid or gaseous form, including mustard gas, lewisite, cyanic acid gas and phosgene in experimental and some operational uses during hostile actions against China. This was effective in spreading fear, terror and death to devastating effect against both humans and livestock.
During the Khabarovsk War Crime Trials, some Japanese soldiers also admitted to have spread Bubonic plague within a 36-km radius around the city (Daniel Barenblatt, A plague upon Humanity, HarperCollns, 2004, pp.220-221).
However, the Japanese action did not achieve its objective, as the Chinese defenders put up additional resistance. Reinforcements from the Chinese army forced the Japanese to retreat and the Chinese retook the city. Furious over their defeat, the Japanese units took revenge by burning the city and massacring civilians during the retreat.