In July 1940 Crerar was sent by the Canadian government to London as Chief of General Staff to plan training programs for Canadian troops. He worked seven days a week to set up the programs but in November 1941 resigned his post and took a lower command in order to see action in the field. He led the I Canadian Corps in Sicily where his troops distinguished themselves at Catania. In 1943 he was recalled to Britain to take command of the 1st Canadian Army, which in fact consisted of Poles, Belgians, Dutch and British units. The army landed near the mouth of the Orne river and was employed to ‘break in’ to Falaise in August 1944. The troops succeeded and then were used to assault the Channel fortresses of Le Havre, Boulogne, Calais and the mouth of the Scheldt. Crerar decided to take each in turn and by 1 October had reached his objective and taken 72,000 prisoners. After clearing the Scheldt and Antwerp his troops moved on to the offensive, southeast of Nijmegen. On 27 February 1944 the army stormed Udem and broke through the last and weakest defenses of the Siegfried Line. Crerar came under MONTGOMERY’s command. He was given a free rein by Montgomery who had faith in him and wanted to please the Canadian government.