Beerfiend comments

Comparing Germany and Japan's admissions of their respective massacres, it is important to note that unlike Germany, Japan was never forced by the United States to admit their guilt and apologize. This may have had something to do with the fact that General Douglas MacArthur granted immunity to several members of the Japanese Imperial Army for war crimes they committed during WWII at a covert biological and chemical weapons research facility in North East China called Unit 731.

The Japanese conducted cruel and painful medical experiments of some 250,000 Chinese men, women and children (without any sort of anesthetic - because that might alter the research results). They operated an on-site crematorium to dispose of the bodies (a process which they called "putting a log on the fire"). The Americans were anxious to get their hands on the resulting research findings from the Japanese, so they let the perpetrators of these crimes off the hook in exchange for the documents. (See Wikpedia and other sources for more details).