The horrors of World War II compelled the Allies to prosecute German and Japanese government officials and military personnel for war crimes. Although WWI provided a precedent, the Allies still confronted many legal, political, and diplomatic challenges to the prosecution of war criminals. How was the International Military Tribunal organized and what were its powers and duties? What standards were used to identify defendants? Was it possible to prosecute individuals for actions not yet defined as criminal at the time they occurred? What kind of defense counsel was provided? Were guilty verdicts presumed? Using a selection of primary sources, we will address these questions as they relate to the trials of German war criminals at Nuremberg, 1945-46.