The Canadian 1st Infantry Division mobilized on 1 September 1939, even before the formal declaration of war, with the 1st Canadian Infantry Brigade, 2nd Canadian Infantry Brigade, and the 3rd Canadian Infantry Brigade. The division crossed the Atlantic in two main convoys at the end of 1939, with additional troops reaching the UK at the beginning of February 1940.
All elements of the division were far from completely equipped: of the artillery and machine guns on hand, most were obsolescent, 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. Only the 1st Canadian Infantry Brigade actually arrived on the continent, and it returned almost immediately. The division trained in the UK for three years before transferring to the Mediterranean to take part in the assault landing on Sicily. It then landed in Calabria and fought its way up the Italian peninsula from Ortona to the Senio with the 8th British Army, earning an excellent reputation along the way.
The 1st moved from Italy as part of Operation Goldflake in March 1945, finishing the war in the Netherlands with Canadian 1st Army.
; 1st Canadian Infantry Brigade :
Formation
; 2nd Canadian Infantry Brigade :
; 3rd Canadian Infantry Brigade :
; Other Units :
(In July 1944, the divisional recon battalion (Princess Louise Dragoon Guards) converted to infantry and transferred to 5th Canadian Armoured Division, to be replaced by The Royal Canadian Dragoons. The Princess Louise returned to its original role in Northwest Europe, and The Royal Canadians became the armored car regiment of I Canadian Corps.)