Cap badge The Ontario Regiment (RCAC), 1st Canadian Corps

The regiment mobilized the The Ontario Regiment (Tank), CASF on 1 September 1939. It was redesignated as The Ontario Regiment (Tank), CASF on 13 August 1940. It was converted to armour on 23 November 1940, and an army tank battalion on 11 February 1941, under the designation 11th Army Tank Battalion (The Ontario Regiment (Tank)), CAC, CASF. It was redesignated the 11th Army Tank Regiment (The Ontario Regiment (Tank)), CAC, CASF, on 15 May 1942 and the 11th Armoured Regiment (The Ontario Regiment), CAC, CASF, on 26 August 1943 and the 11th Armoured Regiment (The Ontario Regiment), RCAC, CASF, on 2 August 1945. On 21 June 1941 it embarked for Britain. The regiment landed in Sicily on 13 July 1943, as part of the 1st Canadian Armoured Brigade, and in Italy on 3 September 1943 in support of 17th Brigade, 5th British Division. On 8 March 1945 the regiment moved with the 1st Canadian Corps to North-West Europe as part of OPERATION GOLDFLAKE, where it fought until the end of the war. The overseas regiment was disbanded on 15 December 1945.

Within six days of mobilization, 594 men had enlisted for active service. In June 1941, the regiment sailed from Halifax on the "Pasteur", arriving in Greenock, Scotland on 1 July, and headed south to Headley Downs, England. The Ontarios were the first Canadians to be issued the Churchill tank with which it trained in exercises in its experimental period of 1941-42. On 21 December 1941 the regiment moved to Brighton, alternating between here and Shermanbury park in operational roles in the defence of the English coast. The unit fought with distinction in several theatres during the war, beginning with the Allied invasion of Sicily in July 1943, through the Italian Campaign (World War II) seeing action in the fierce Liri Valley, Monte Cassino, and on to Ortona. In 1945, the unit entered the Northwest European theatre where it fought with distinction in the Dutch Campaign winning honours at Arnhem.