The division was remobilized, as the 1st Canadian Infantry Division, before Canada's formal entrance into the Second World War, along with the 2nd Canadian Infantry Division and the 3rd Canadian Infantry Division. The division left Halifax from Pier 21 in two heavily escorted convoys, the first departing on December 10 and the second on December 22, 1939, with additional troops reaching the United Kingdom at the beginning of February 1940.[2] In 1941, the formation adopted the red rectangular battle patch insignia worn by the 1st Canadian Division in the First World War.
All elements of the division were far from completely equipped on mobilization: of the artillery and machine guns on hand, most were obsolete, and the troops lacked steel helmets. Only gradually did a full complement of more modern weapons, equipment, and transport begin reaching the division in 1940.
Nevertheless, in the wake of the Dunkirk evacuation the Canadians were ordered to France in June 1940. Among the Infantry units that landed at Brest, France were The Royal Canadian Regiment (RCR), The 48th Highlanders of Canada and The Hastings and Prince Edward Regiment. Members of the RCR were present in France at least until 16 June, after Paris had fallen to German forces, and returned almost immediately after. The 48th withdrawal was not without some excitement.
The division returned to England where it became the only fully equipped and trained force trained for the defense of England in the case of a German invasion. It eventually stayed in England for another three years before transferring to the Mediterranean theatre where it took part in Operation Husky, the Allied assault landing on Sicily in July 1943, which ended after just 38 days. The division, now commanded by Major-General Guy Simonds, came under command of British XIII Corps, serving alongside the veteran 51st (Highland) Division, part of the British Eighth Army, commanded by General Bernard Montgomery. Soon after the conquest of Sicily, the division, still under XIII Corps but now serving alongside the British 5th Infantry Division (which had also fought in Husky), then landed in Calabria as part of Operation Baytown on the Italian mainland and fought its way up the Italian peninsula, participating in the Moro River Campaign and, supported by tanks of the 1st Canadian Armoured Brigade, squaring off in the seaside town of Ortona with German Fallschirmjäger – crack air force paratroops of the 1st Parachute Division – over Christmas 1943. Both sides suffered heavy losses in the fight for the town which a reporter forThe New York Times had begun calling a "miniature Stalingrad", based on the ferocity of the street fighting and the losses, [3]with the Canadians suffering 650 casualties. By December 27, what remained of Ortona, after days of shelling and aerial bombardment, was in Canadian hands. It then went on to break out of the Eighth Army's bridgehead with the second wave in the spring offensive, Operation Diadem, in May 1944. The 4th Princess Louise Dragoon Guards, the reconnaissance (or 'recce') regiment serving with 1st Canadian Division, was the first of the Eighth Army's units to cross the Hitler Line in May 1944, below Pontecorvo in its armoured cars.
After heavy fighting in front of the Gothic Line throughout the summer, the 1st Canadian Infantry Division spent the next several months fighting, as it had the previous fall, for a succession of heavily-defended river crossings surrounded by high ground. By the time the division reached the Senio, as the icy rain began giving way to snow in the Canadian sector, a decision had been reached to transfer the entire 1st Canadian Corps, 1st Infantry Division included, to the Netherlands.[4] By the end of March, 1945 all Canadian Army units serving with Allied Forces Mediterranean had been transferred and Operation Goldflake, the reunion of 1st Infantry and 1st Armoured Brigade and First Canadian Army, commanded by Lieutenant-General Henry Duncan Graham Crerar, accomplished.