For its part, the Japanese government did not acknowledge the existence of Unit 731 until recently. When it became apparent that Japan would be defeated, Japanese soldiers destroyed the headquarters of Unit 731.

The Chinese later rebuilt some of the main buildings and began setting up a museum in 1982.

Eight years ago, 180 Chinese victims and families of victims sued the Japanese government, demanding an apology, compensation and a full disclosure of Unit 731’s activities.

Last month, the Tokyo High Court acknowledged the existence of Unit 731 but upheld a lower court ruling that denied the plaintiffs compensation.

None of the Japanese scientists in Unit 731 was ever punished.

In 1946, US General Douglas MacArthur granted all the Japanese scientists immunity from war crimes prosecution in exchange for the germ warfare data gathered from experiments in Harbin.

As explained in an internal War Department memorandum, dated June 23, 1947: “Since it is believed that the USSR possesses only a small portion of the technical information, and since any war-crimes action would completely reveal such data to all nations, it is felt that such publicity must be avoided in the interests of defense and security of the U.S.

It is believed also that the war-crimes prosecution of Gen. Ishii and his associates would serve to stop the flow of much additional information of a technical and scientific nature.”

Gen. Ishii lived on the outskirts of Tokyo until his death in 1959. Other “graduates” of Unit 731 include the former governor of Tokyo, the former president of the Japan Medical Association, the former director of the health ministry’s preventive health research centre, the former chairman and president of Green Cross Corp. and the past heads of a number of Japanese medical schools. The man in charge of vivisections, Yoshisuke Murata, became director of the respected Kyoto University medical school, and later medical director at Kinki University.

In 1981, a fictionalized work by journalist Seiichi Morimura was published called Gluttonous Devils, which was based in part on interviews with surviving Japanese who worked at the laboratory. It was filled with accounts of victims being subjected to freezing, high pressure and vivisection.