They knew that a war crime was devastation beyond military necessity. It was a rape, a pillage, plunder. These were things that for many years had been codified as the rules of warfare but they didnt deal with questions like aggressive war being a crime. These were the things which came later with the military tribunal and were generated by the fact people like Justice Jackson as well as the other the british distinguished judges and lawyers who were represented on that, these were people who were familiar with the broader principles and concepts of International Law and justice whereas in the army it was just like, you know, another g. I. Trial where you bring in the accused, hes represented by another officer or another individual and the judges happen to be Army Officers who are available to hear