By then a first lieutenant ("Oberleutnant"), he volunteered to join the Luftwaffe's parachute troops, the Fallschirmjäger. As company commander in the 9th Fallschirmjäger Regiment (part of the 3rd Parachute Division), he fought in the Ardennes Offensive, in the Ruhr Pocket, and at the battle of Hürtgenwald. Luther became an American prisoner on 28 April 1945, and was freed in December 1945.