Unit 731 (Japanese: 731部隊, Hepburn: Nana-san-ichi Butai), short for Manshu Detachment 731 and also known as the Kamo Detachment and Ishii Unit, was a covert biological and chemical warfare research and development unit of the Imperial Japanese Army that engaged in lethal human experimentation and biological weapons manufacturing during the Second Sino-Japanese War (1937–1945) and World War II. It was based in the Pingfang district of Harbin, the largest city in the Japanese puppet state of Manchukuo (now Northeast China) and had active branch offices throughout China and Southeast Asia.