HQ was disbanded and he remained temporarily unemployed. On his return to service in August he was, upon the recommendation of Alexander to Brooke, given command of I Corps in early August. Crocker took over from Lieutenant-General Gerard Bucknall, who had requested demotion to temporary major-general to command a division overseas. Crocker's I Corps was to form part of the British Second Army, then under his former army commander in North Africa, Lieutenant-General Sir Kenneth Anderson (but replaced in January 1944 by Lieutenant-General Miles Dempsey), training for Operation Overlord, the Allied invasion of Northern France. Crocker was to aided throughout by his BGS, Philip Balfour. Despite Crocker's background in armoured warfare, I Corps was predominantly an infantry formation, but General Sir Bernard Montgomery, the Allied Land Forces Commander for D Day and the battle of Normandy 21st Army Group, had confidence in Crocker's organisational skills and assigned I Corps the difficult task of capturing the city of Caen. For the landings I Corps had under command the 3rd Canadian Division, supported by the 2nd Canadian Armoured Brigade, and Major-General Tom Rennie's British 3rd Division, supported by the 27th Armoured Brigade, and Major-General Richard Gale's 6th Airborne Division. On D-Day, 6 June 1944, Crocker had a larger task than any other Allied corps commander: he had to control two landing beaches (Juno and Sword) and an airborne assault. The fact that, in spite of inevitable mishaps, the landings went so well was a testimony to Crocker's planning. However, Caen did not fall on D-Day as planned, although a battalion of the British 3rd Division made a spirited attempt before being driven back by the 21st Panzer Division. Instead, Crocker's corps took part in the bloody two-month Battle for Caen, including Operation Charnwood, which still had the 3rd Canadian and 3rd British Divisions under command (the latter now under Major-General Lashmer Whistler after Rennie was injured), along with Major-General Lewis Lyne's 59th Division. The operation began on 7 July and, after heavy fighting, had captured most of the Caen city centre, although the Germans still held the southern half. The corps, losing the 3rd Division soon after and gaining Major-General Evelyn Barker's 49th Division in exchange, came under command of Lieutenant-General Harry Crerar's First Canadian Army in August 1944, I Corps drove forward to the River Seine and then took part in the unglamorous mopping up operations along the French and Belgian