[littlefisherman]

731 troops is a Japanese troops during World War II and Anti-Japanese War (1937-1945) which was engaged in biological warfare and germ warfare research and human trials related research a secret military medical unit. 731 troops was disguised as a water purification unit. 731 troops base was built in Harbin, northeast China near the cottage area, this area was part of the puppet regime in Manchukuo. Some researchers believe that more than 10,000 Chinese, Koreans, as well as the coalition forces of prisoners of war were in the 731 test victims, but the number is still in dispute.
Japanese right-wing nationalist historians have denied the 731 movements of troops, they think it is China's propaganda. At the same time, the left-wing organizations have published 731 history, saying that the United States deliberately concealed the facts in exchange for 731 units of research data. Now the history of 731 troops and others involved topics during World War II as well as the controversy have been cancelled in the Japanese text books, but more and more evidence show that this troop did exit during that period.

[Smilin' Dave]

saying that the United States deliberately concealed the facts in exchange for 731 units of research data

More than that, members of 731 ended up working in the US and Japan in medical fields, Shiro Ishii is alleged to have continued to work with bio-weapons. On the other hand, the Soviets used materials from Unit 731 to create a bio-weapons facility in Sverdlovsk. This did not bother the CCP apparently, as the two countries remained allies for much of the 1950s.