A search for evidence of Imperial Japanese or Nazi war crimes turns up a lot of information. In contrast, the results of a search for Allied atrocities is rather thin. Even documentation of the barbaric and vengeful Russian invasion of eastern Germany at the end of the war is scant compared with records of the holocaust or Japan’s China campaign.
There is no question that the Axis powers committed numerous terrible atrocities in WWII. Imperial Japan did not sign and completely ignored the rules of war as designated by the Geneva conventions. Nazi Germany systematically murdered large civilian populations.
But the Allies were not always boy scouts, fighting clean and hard. Although the number of documented Allied atrocities was relatively small compared with the Axis powers, the Allies also committed war crimes.
The myth of a chivalrous and honorable war is fantasy. War produces atrocities on all sides. And the axiom rings true: the victor gets to write the history.
Read more:
https://en.wikipedia.org/wiki/Allied_war_crimes_during_World_War_II
http://www.theguardian.com/world/2001/jun/03/humanities.highereducation