The war crimes tribunal tried and punished personnel only from Axis countries. Accusations arose claiming victor's justice, since no war crimes by the Allies were heard. It is, however, usual that the armed forces of a civilized country issue their forces with detailed guidance on what is and is not permitted under their military code. These are drafted to include any international treaty obligations and the customary laws of war. For example, at the trial of Otto Skorzeny, his defence was in part based on the Field Manual published by the War Department of the United States Army, on 1 October 1940, and the American Soldiers' Handbook. If a member of the armed forces breaks their own military code, they can expect to face a court martial. When members of the Allied armed forces broke their military codes, they could be and were tried, as, for example, at the Biscari Massacre trials.
However, General Chuck Yeager writes in his autobiography that some air corps missions were probably war crimes, (specifically, the 'shoot anything that moves' missions in the German countryside) but he, and other pilots, went on the missions in order to avoid court martial for disobeying orders. He also said he hoped the allies won the war, otherwise they might be tried for war crimes.
The unconditional surrender of the Axis powers was unusual and led directly to the formation of the international tribunals. Usually, international wars end conditionally and the treatment of suspected war criminals makes up part of the peace treaty. In most cases, those who are not prisoners of war are tried under their own judicial system if they are suspected of committing war crimes – as happened to some Finns at the end of the concurrent Finnish-Soviet Continuation War. In restricting the international tribunal to trying suspected Axis war crimes, the Allies were acting within normal international law.