In World War II he commanded a corps in the North African and Sicilian campaign. He commanded US land forces in the Normandy Campaign, and later, following the Ardennes Campaign, went beyond Eisenhower’s orders to link up with the Soviet forces on the Elbe in 1945. He was instrumental in building up NATO, formulating US global defence strategy in the post-war years, and in committing US troops to fight in the Korean War.