Winter 1942-1943: in the North Atlantic, winter storms raged with gigantic waves and gusts of winds. But there were worst threats: the number of German submarines, the dreaded U-boats, was growing. Hunting in packs of up to 20 submarines, they targeted Allied convoys. These attacks were so destructive that they threatened to bring transatlantic shipping to a halt, making impossible the invasion of Europe. During the first twenty days of March 1943, 85 Allied ships were torpedoed and sunk. These were the darkest hours of the Battle of the Atlantic.

Dark hours for Royal Canadian Navy escort groups as well, as they were severely criticized by Western Approaches Command. In March 1943, three of the four Canadian escort groups were pulled away from the Mid-Ocean Escort Force for additional training at the Royal Navy base in Londonderry. They were then assigned to the Great Britain-Gibraltar route used by convoys involved in Operation Torch, the invasion of North Africa.

And then, the wind shifted direction…

A Change in the Balance of Power

A "hedgehog" on board HMCS Moose Jaw, Halifax, May 1st, 1944. Department of National Defence / National Archives of Canada, PA-112918.

If the U-boat fleet was growing, the number of Allied convoys, freighters, tankers and escort ships increased as well, in part through the efforts of the Canadian shipping industry. Improved ASDIC, radar and radio direction finding systems were installed on Allied vessels allowing them to better locate and hunt down German submarines. A new weapon, the "Hedgehog" was coupled to the ASDIC and could fire up to 24 mortar shells of 30 kg in front of a frigate or corvette. British intelligence services broke the new Enigma cipher allowing the Allies to intercept U-boat radio messages. Air patrols became more frequent and longer-ranged, flying from air bases in Iceland, Newfoundland or Great Britain.

The creation of support groups separate from escort groups made it possible to hunt down U-boats with some efficiency and without leaving convoys unprotected from attacks by other submarines of the pack.

In April 1943, the command of escort forces in the Atlantic was once more restructured: Western Approaches Command remained responsible for North Atlantic convoy operations east of Newfoundland; the US Navy was responsible for operations in the South Atlantic, including the Great Britain-Mediterranean route. The Royal Canadian Navy was put in charge of operations in the North West Atlantic. Rear Admiral L.W. Murray was appointed as commander in chief for that new theatre.

The following month, the three "C" (i.e. Canadian) escort groups completed their training and returned to the North West Atlantic sector. All ships were upgraded to improve their combat worthiness. Other Royal Canadian Navy ships were to be upgraded as well as the war went on, but the gap between Canadian and Royal Navy ships was never filled. In June 1943, the first Canadian-built frigates were commissioned.

In May, all those measures began to have a definite impact. In three weeks and a half, 30 U-boats were destroyed by the Allies, in regard of 50 merchant ships sunk. Between June and August 1943, 80 U-boats were destroyed or seriously damaged. Admiral Karl Dönitz was forced to order his submarines to avoid Allied convoys.

Even if the balance of forces changed within a few weeks, the submarine threat remained a major one. German naval engineers continued to improve U-boats and their weapon systems. In September 1943, the Kriegsmarine introduced the acoustic torpedo that could follow a sound source such as a propeller. That new weapon had devastating effects until the Allies came up with a sound-producing device that attracted the torpedo far enough from the hull so that it would explode without causing harm. In early 1944, the schnorkel was introduced, a device that allowed a continuous supply of fresh air while the submarine was just below the surface. U-boats thus equipped could stay below the surface for days on end, almost invisible but able to use their powerful diesel engines.

Starting in the summer of 1943, the German Navy found itself unable to regain the advantage in submarine warfare; Allied losses diminished and merchant ship convoys were now able to deliver supplies unhampered. The volume of goods to be shipped to Great Britain was enormous: for D-Day alone, some ten million tonnes of supplies were required.

Combined Operations

LCI(L) 299 of the 2nd Canadian flotilla ferrying soldiers of the 9th Canadian Infantry Brigade towards Normandy beaches, June 6th, 1944 Photo by Gilbert A. Milne. Department of National Defence / National Archives of Canada, PA-136986.

The Royal Canadian Navy ensured convoy escorts operations in the North Atlantic up to the very last weeks of the war, in May 1945. It also took part in those large-scale combined (Army, Navy, Air Force) operations that started in 1943: the invasion of North Africa in November 1942, the invasion of Sicily in July 1943, the landing of Allied forces in Italy in September 1943; as well as support operations required for the campaign in Northwest Europe, from June 6th, 1944, to the Armistice.

The Royal Canadian Navy's participation in combined operations took different forms. From 1943 onwards, speedboats patrolled the Channel; Canadian-flagged minesweepers ensured the safe passage of invasion flotillas in mine-infested waters. The RCN landing crafts got Canadian and British soldiers to their destination. And naturally, Canadian frigates and corvettes took part in landing operations, protecting the Allied fleet against enemy submarines and warships.