He saw action in the First World War, when he was seriously wounded, and during the Second World War he commanded the 8th Army from August 1942 in the Western Desert until the final Allied victory in Tunisia. This command included the Battle of El Alamein, a major turning point in the Western Desert Campaign. He subsequently commanded Eighth Army in Sicily and Italy before being given responsibility for planning the D-Day invasion in Normandy. He was in command of all Allied ground forces during Operation Overlord from the initial landings until after the Battle of Normandy. He then continued in command of the 21st Army Group for the rest of the campaign in North West Europe.