The role of the international tribunal after the second world war was to fix responsibility for the crimes committed by the German government during the war and punish the leading Nazis who were responsible for those crimes.
The tribunal tried and convicted many leading Nazi figures. The tribunal tried 24 leading members of the Nazi government who had survived the war. It sentenced 12 of them to death.
The difference that the tribunal made was that this was the first time that war criminals like the Nazis were made to face responsibility for their crimes against humanity.