A dramatized, extremely graphic account of Unit 731, the Imperial Japanese Army's real wartime biological and chemical warfare research unit in occupied Manchuria, which conducted horrific human experimentation on prisoners of war and civilians under the guise of medical research. Directed by Tun Fei Mou, the film became notorious on release for blurring dramatization with what were reported to be genuine, unsimulated scenes of animal cruelty and human dissection footage, making it one of the most controversial "based on true events" war-horror films ever released, still banned or heavily cut in numerous countries.