The Fifteenth United States Army was the last field army to see service in northwest Europe during World War II and was the final command of General George S. Patton. The Fifteenth Army served two separate missions while assigned to the area. During the later stages of World War II its mission was training and rehabilitating units and acting as a defensive line against counterattacks. After the war its mission was to carry out occupation duties and to gather historical information related to the European Theater of Operations, or ETO. The Fifteenth Army was inactivated in 1946 and has not been activated since.