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. In 1937 the prison camp was destroyed and testing operations were transferred to Pingfang under Unit 731.
Background
In 1930 Doctor Shirō Ishii, an Imperial Japanese Army researcher in biological and chemical warfare, petitioned the Japanese War Ministry to establish a biological weapons program. With the support of Army Minister Sadao Araki and the dean of the Tokyo Army Medical College, Koizumi Chikahiko, a biological weapons program was initiated under a newly formed department of immunology. Ishii began his research in biological warfare as the head of the "Epidemic Prevention Research Laboratory." Although protecting Japanese troops from disease was part of the agenda, the laboratory's primary objective was to develop an effective means to spread epidemics. Ishii relocated his laboratory to a military facility near Harbin. However, the facility's highly populated surroundings threatened to compromise the secrecy of the ongoing human experimentation. Consequently, a second site, about 100 kilometers to the south of Harbin at the village of Beiyinhe, was selected. Beiyinhe was a diffuse village of about 300 homes known to the local populace as Zhong Ma City. The Imperial Japanese Army cleared out the local inhabitants and burnt down the village, except for a large building suitable for use as a headquarters. at the time of the traditional summer festival, the prisoners were given a ration of special foods. One prisoner, named Li, managed to overpower his guard, seize the keys and freed about forty of his fellow prisoners. Although their legs were shackled, their arms were free, and the prisoners were able to climb the outside walls. A heavy downpour had knocked out the facility's electricity, deactivating the searchlights and electric fence. Some ten of the escapees were shot by guards while others were recaptured and subjected to sadistic treatment as reprisal, but roughly sixteen managed to escape. Some of the men soon died from exposure, hunger, cold, and the injuries from their experiments but several managed to survive, and spread word of the crimes against humanity being conducted by Shiro and his subordinates. Although the Kuomintang took no notice of these reports, Zhongma Fortress was closed down due to the significant publicity, and its activities transferred to a new site closer to Harbin called Pingfang (Heibo), which came to be known as Unit 731. The testimony of one of the escapees, Ziyang Wang, was collected by Xiao Han, deputy director of the Pingfang museum, in the 1980s.