Unit 731 (Japanese: 731部隊, Hepburn: Nana-san-ichi Butai), also referred to as Detachment 731, the 731 Regiment, Manshu Detachment 731, The Kamo Detachment, or the Ishii Company, was a covert biological and chemical warfare research and development unit of the Imperial Japanese Army that undertook lethal human experimentation during the Second Sino-Japanese War (1937–1945) of World War II.