Zhongma Fortress

Zhongma Fortress (Chinese: 中馬城) — also Zhong Ma Prison Camp or Unit Tōgō — was a prison camp where the Japanese Kwantung Army carried out covert biological warfare research on human test subjects. Built in Beiyinhe, outside of Harbin, Manchukuo during the Second Sino-Japanese War, the camp served as a center for human subject experimentation and could hold up to 1,000 prisoners at any given time.^[1] In 1937 the prison camp was destroyed and testing operations were transferred to Pingfang under Unit 731.