With the recent move by President Trump to issue pardons to some U.S. soldiers that were either charged with or convicted of war crimes, it is fitting that the largest war crimes trials in history and the ones that changed how the world treats war crimes began on this day in 1945.

These trials would last from November 20, 1945 to October 1, 1946. Of the initial 24 men tried, 12 would be found guilty (one in absentia) and hanged. Of the rest, three were acquitted; one was found unfit for trial by reason of bad health; one committed suicide before the trial could commence; and one was indicted incorrectly and not tried. The rest were given long prison sentences. 

This trial was significant because something of this scope had never been attempted before. (Of a smaller scale, in the United States, Henry Wirz was convicted of war crimes and executed over the maltreatment of Union prisoners of war at Andersonville prison during the Civil War. The Turks also held a trial in 1920 for the 1915-1916 Armenian Genocide.) 

But besides its scope, another novelty of the trial was that four different legal systems (British, French, American, and Soviet) would be applied to try the alleged illegal and criminal activities of a fifth nation (Nazi Germany). Therefore, the rules of the trial had to be worked out beforehand.