Royal Canadian Navy (RCN)

• Began the war with 13 vessels, of which 6 were destroyers, and 3,500 personnel, and ended it with the third largest navy in the world. At war's end the RCN had 373 fighting ships and over 110,000 members, all of whom were volunteers, including 6,500 women who served in the Women's Royal Canadian Naval Services.
• Escort of merchant ship convoys was the RCN's chief responsibility during the Battle. The first convoy sailed from Halifax on September 16, 1939, escorted by the Canadian destroyer St. Laurent. By mid-1942, the RCN, with support from the RCAF, was providing nearly half the convoy escorts, and afterward carried out the lion's share of escort duty.
• Approximately 2,000 members of the RCN died during the war, and 24 RCN vessels were sunk.
• Canadian aircraft and ships, alone or in consort with other ships or aircraft, sank 50 U-boats.

Merchant Marine

• On August 26, 1939, all Canadian merchant ships passed from the control of their owners to the control of the RCN. No Canadian-registered ship or merchant ship in a Canadian port could sail without the RCN's authority and direction.
• When the war began Canada had 38 oceangoing merchant vessels of 1,000 tons or more. 410 merchant ships were built in Canada during the war.
• More than 25,000 merchant ship voyages were made.
• The Merchant Navy Book of Remembrance lists the names of approximately 1,600 Canadians who died at sea during the war, including those of eight women.

U-boats (Unterseebooten)

• German submarines, main threat to merchant and other surface vessels. Were capable of remaining away from port for three months and more. When submerged, operated on batteries which, until the schnorkel was invented, had to be re-charged by their diesel engines at surface level. Carried up to 21 torpedoes and also laid mines. Could dive below the surface in roughly 30 seconds.
• In one month — June 1941 — over 500,000 tons of Allied shipping were lost to U-boats.
• U-boats improved with acoustic torpedo and schnorkel, which drew air inside sub and expelled exhaust fumes, allowing vessel to recharge its batteries while beneath the surface. First appeared in late 1943.
• By March 1945, 463 U-boats were on patrol, compared to 27 in 1939.