@oristarA,
The Guardian is not USA media.
The USA let the folks of Unit 731 go free in exchange for all their dirty secrets. You see, the USA doesn't care about justice for others, they only care about advancing their position in the world to rape and pillage.
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http://en.m.wikipedia.org/wiki/Unit_731
American grant of immunity
After Imperial Japan surrendered to the Allies in 1945, Douglas MacArthur became the Supreme Commander of the Allied Powers, rebuilding Japan during the Allied occupation. MacArthur secretly granted immunity to the physicians of Unit 731, including their leader, in exchange for providing America, but not the other wartime allies, with their research on biological warfare.[9] American occupation authorities monitored the activities of former unit members, including reading and censoring their mail.[32] The U.S. believed that the research data was valuable. The U.S. did not want other nations, particularly the Soviet Union, to acquire data on biological weapons.[33]
The Tokyo War Crimes Tribunal heard only one reference to Japanese experiments with "poisonous serums" on Chinese civilians. This took place in August 1946 and was instigated by David Sutton, assistant to the Chinese prosecutor. The Japanese defense counselor argued that the claim was vague and uncorroborated and it was dismissed by the tribunal president, Sir William Webb, for lack of evidence. The subject was not pursued further by Sutton, who was likely unaware of Unit 731's activities. His reference to it at the trial is believed to have been accidental.
Separate Soviet trials
Although publicly silent on the issue at the Tokyo Trials, the Soviet Union pursued the case and prosecuted twelve top military leaders and scientists from Unit 731 and its affiliated biological-war prisons Unit 1644 in Nanjing, and Unit 100 in Changchun, in the Khabarovsk War Crime Trials. Included among those prosecuted for war crimes including germ warfare was General Otozō Yamada, the commander-in-chief of the million-man Kwantung Army occupying Manchuria.
The trial of those captured Japanese perpetrators was held in Khabarovsk in December 1949. A lengthy partial transcript of the trial proceedings was published in different languages the following year by a Moscow foreign languages press, including an English language edition.[34] The lead prosecuting attorney at the Khabarovsk trial was Lev Smirnov, who had been one of the top Soviet prosecutors at the Nuremberg Trials. The Japanese doctors and army commanders who had perpetrated the Unit 731 experiments received sentences from the Khabarovsk court ranging from two to 25 years in a Siberian labor camp. The Americans refused to acknowledge the trials, branding them communist propaganda.[35]