The Battle of the Atlantic, 1939-1945

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Navy News / April 30, 2021

Every year on the first Sunday in May, the Canadian Navy family gathers to commemorate the Battle of the Atlantic – to honour the struggle, sacrifice, and loss, but also to celebrate the heroism and courage in the face of daunting obstacles: horrible weather and high seas, rough little ships and cramped quarters, and the ever-present threat of attack by submarines lurking below.

Because we can’t gather in person this year, the 76th anniversary of the end of that Battle, it may be more important than ever to know more about what we are commemorating, and why.


What was the Battle of the Atlantic? Why does it matter?

The importance of the Battle of the Atlantic simply can’t be overstated: it is universally acknowledged that without victory in the Atlantic, Allied victory in the Second World War would not have been possible.

Even British Prime Minister Winston Churchill, not known for expressing doubt or fear, wrote in his memoirs that the only thing that ever really frightened him during the war was the threat posed by German submarines in the Battle of the Atlantic.

It was the longest Battle of the Second World War, lasting from the outbreak of hostilities in September 1939 until victory in Europe in May 1945. It completely transformed the Royal Canadian Navy from a tiny, ill-equipped and under-trained force into one of the largest navies on earth, quickly expanding to fifty times the personnel and hundreds of ships.

Victory came with a high cost: 4,600 Canadian lives, including members of the Navy, the Royal Canadian Air Force, the Merchant Navy, and the Wrens (the Women's Royal Canadian Naval Service).


How did it start? Why was it necessary?

With continental Europe under Germany’s control, the United Kingdom stood alone against the Nazi threat. To sustain Britain’s war effort, supplies of food and war materials from the rest of the world had to be shipped there. To try to cut Britain off and starve the island nation into submission, Germany used all-out submarine warfare – making no distinction between military warships and civilian merchant vessels. In response, convoys were formed, with warships (called escorts) protecting the merchant ships carrying the supplies. In addition to the Atlantic convoys, there were Arctic convoys that carried vital supplies to the northern ports of the Soviet Union, to help that country in its fight against Nazi Germany.

The strategy of the convoys was to place ships together in a relatively small area to give the enemy less open space in which to attack, and to increase enemy losses by concentrating the escorts. But the escorts were often outnumbered, ill-equipped, and short of sailors, with those they had often having been hastily trained.



There were two main types of convoys:

Slow convoys (SC) were ships that went less than 9 knots, usually even slower, with 7 knots being a common speed. They went from Sydney, Nova Scotia to Liverpool, UK, taking about 20 days. There were 117 of these convoys during the Battle of the Atlantic, with a total of over 6800 ships, of which about 340 were lost.

Fast convoys (HX) left from Halifax, and later New York City, and typically made the crossing to England in 15 days. There were 377 of these convoys, for a total of more than 20,000 ships, with 200 ships lost.

The largest convoy of the war was HX 300 in July-August 1944, with over 160 ships. It arrived without incident and with no losses.

The main Canadian escort ships for these convoys were the corvette, the frigate, and the destroyer (see photos).


Anti-Submarine Warfare

With the enemy conducting unrestricted submarine attacks, the greatest challenge was Anti-Submarine Warfare, or ASW, and early in the war, the Allies were not well prepared to meet the challenge. The main ASW weapons were ASDIC (sonar) and depth charges launched from ships to attack submarines below. Both had limited effectiveness: sonar only worked when the submarine was submerged but U-boats (German submarines) routinely operated on the surface at night. With depth charges, the ship had to break sonar contact to use them because they were delivered from the stern while the sonar pointed forward.

However, with mounting losses of lives and ships as motivators, ASW weapons and tactics improved rapidly over the course of the war, to the point where the Allies eventually had the upper hand on the U-boats. The development of multi-ship tactics, where one ship tracked the U-boat while others attacked, helped reduce losses, as did the deployment of forward-throwing weapons such as the Hedgehog and the Squid.

Newer technologies like radar and HF/DF, though slow to be installed in Canadian corvettes, also helped turn the tide in the battle against submarines. HF/DF (‘Huff-Duff’), short for High-Frequency Direction Finding, allowed ships to pick up radio transmissions from U-boats and track their locations. The capture of the Enigma machine, a German encryption device, allowed the Allies to decode U-boat transmissions, and this ability to decode, combined with HF/DF, allowed the Allies to track, intercept, and translate U-boat communications, offering a decisive advantage.


The cost: ships lost in the Battle of the Atlantic

Every year on Battle of the Atlantic Sunday, a bell is rung for each of the ships lost during the battle, and for the lives lost with them.

  • Adversus - 20 Dec 1941. Ran aground, McNutts Island, near Shelburne, NS, none lost.
  • Alberni - 21 Aug 1944, English Channel, 49 lost.
  • Athabaskan - 29 Apr 1944, sunk by enemy torpedo, North of Île Vierge, off the coast of Brittany (France), 128 lost.
  • Bras D’or - 19 Oct 1940, St. Lawrence River, 30 lost.
  • Charlottetown - 11 Sep 1942, St. Lawrence River, 10 lost.
  • Chedabucto - 21 Oct 1943, St. Lawrence River, 1 lost.
  • Clayoquot - 24 Dec 1944, Halifax Approaches, 8 lost.
  • Esquimalt - 16 Apr 1945, Halifax Approaches, 44 lost. Last Canadian Warship to be sunk, Second World War.
  • Fraser - 25 Jun 1940, Bay Of Biscay, 47 lost.
  • Guysborough - 17 Mar 1945, Bay Of Biscay, 51 lost.
  • HDC 15 (Harbour Defence Patrol Craft) - 14 Apr 1943, Saint John, NB, 6 lost.
  • Lévis - 19 Sep 1941, North Atlantic, 18 lost. First corvette sunk in Second World War.
  • Louisbourg - 6 Feb 1943, Western Mediterranean, 37 lost.
  • Margaree - 27 Oct 1940, Northeastern Atlantic, 142 lost.
  • MTBs (Motor Torpedo Boats) 459, 461, 462, 465, 466 - 14 Feb 1945, Ostend, Belgium, 26 lost.
  • MTB 460 - 2 Jul 1944, English Channel, 11 lost.
  • MTB 463 - 8 Jul 1944, English Channel, none lost.
  • Ottawa - 13 Sep 1942, North Atlantic, 113 lost.
  • Otter - 26 Mar 1941, off Halifax, 19 lost.
  • Raccoon - 7 Sep 1942, St. Lawrence River, 37 lost.
  • Regina - 8 Aug 1944, Northern coast, Cornwall, 30 lost.
  • St Croix - 20 Sep 1943, North Atlantic, 147 lost.
  • Shawinigan - 24 Nov 1944, Cabot Strait, 91 lost.
  • Skeena - 25 Oct 1944, Iceland, 15 lost.
  • Spikenard - 10 Feb 1942, North Atlantic, 57 lost.
  • Trentonian - 22 Feb 1945, English Channel, 6 lost.
  • Valleyfield - 6 May 1944, Northwestern Atlantic, 123 lost.
  • Weyburn - 22 Feb 1943, Strait Of Gibraltar, 8 lost.
  • Windflower - 7 Dec 1941, Northwestern Atlantic, 23 lost.
  • Ypres - 12 May 1940, Halifax, none lost.


Air cover and the mid-Atlantic gap

Air power was an essential part of the Battle of the Atlantic, with both the Royal Canadian Air Force and the RCN’s own naval aviators protecting convoys by spotting and hunting submarines. However, with the limited range of aircraft at the time, there was a section of the Atlantic that could not be reached by land-based warplanes. In this Mid-Atlantic Gap, called the Black Pit by sailors, the convoys were especially vulnerable, but by May 1943 the gap was closed thanks to the increasing use of Very Long Range Liberator bombers and Escort Aircraft Carriers.


The legacy 

During convoy duty in the Battle of the Atlantic, HMC Ships sank 33 enemy submarines: not insignificant, but a small percentage of the 1000 subs sunk by the Allies in the war. The true measure of success was in safely escorting merchant ships, and in this the RCN made its mark. A very large portion of the 25,000 ships shepherded safely across the Atlantic got there under Canadian escort. In the struggle against the U-boats, and the lessons learned from it, the RCN found its area of expertise for the next 50 years, in anti-submarine warfare.


Heroes of the Battle of the Atlantic

Any battle is about more than facts and figures. It is about the people who fought, and their stories of courage and grit. Here are just a few of those stories, but there are many more. You can read about other Canadian Naval Heroes here.

Max Bernays was Coxswain of His Majesty's Canadian Ship (HMCS) Assiniboine during the sinking of German submarine U-210, where he ordered the two other sailors out of the burning wheelhouse, remaining there alone to give dozens of helm and engine telegraph orders to aid in fighting the ship. Awarded the Conspicuous Gallantry Medal for his actions, Bernays has one of the RCN’s new Arctic & Offshore Patrol Vessels (AOPVs) named for him.

Margaret Brooke, an RCN Nursing Sister, was aboard the ferry SS Caribou when it was torpedoed and sunk off the Newfoundland coast. For her valiant attempt to keep a fellow nursing sister alive in the freezing water, SLt Brooke was made a Member (Military Division) of the Order of the British Empire (MBE). One of the RCN’s OPVs is named for her. 

Harry DeWolf was Commanding Officer of HMCS Haida, known as the “Fightingest Ship in the Royal Canadian Navy.” Haida sank more enemy tonnage than any other Canadian warship. The first of the RCN’s AOPVs is named in his honour. 

Walter Hose headed Canada’s navy as Chief of the Naval Staff, 1928 to 1934. Credited with saving the Royal Canadian Navy during the interwar years. Created the Royal Canadian Naval Volunteer Reserve (RCNVR), which was instrumental in providing the personnel to fight the Battle of the Atlantic.

John Stubbs was Commanding Officer of HMCS Assiniboine during the sinking of German submarine U-210, where he earned a Distinguished Service Order (DSO). He was Commanding Officer of HMCS Athabaskan when that ship was sunk off the coast of France, killing LCdr Stubbs and 127 others.


This article is presented as a general overview of the Battle of the Atlantic. For a more comprehensive account, please see this chapter of The Naval Service of Canada 1910-2010, published for the RCN’s Centennial.