The Allies declared themselves judicial power to define what a war criminal was an prosecute the German and Japanese military leaders, torture them to get false confessions and prosecuting them on the same things that the Allies did.
Ex. Curtis LeMay firebombed and burned 100k citizens of Tokyo alive in ONE NIGHT. The British erased Dresden from the face of the map. LeMay (and Robert Macnamara) later said if the Japanese had won the war, they would have been convicted and executed as war criminals.
Why do we have such a biased view of WWII? Why do we accept everything we are told? Why don't people know that Hitler wanted an alliance with UK/France against the USSR? Why don't people realize history is written by the victor?