The Battle of the Atlantic, 1939 to 1945

The war against the U-boats from 1939 to 1945 was the formative experience for the Royal Canadian Navy (RCN) in the twentieth century.

Painting depicts many ships at a harbour as men work to secure the ropes for ships coming into the docks.

Halifax – The Spring Board by John Horton, in which the flurry of dockyard activity during the Second World War is clearly evident.

Fought largely by reservists in small ships built in Canada and operating from Canadian bases, the defence of North Atlantic trade against the submarine menace defined a naval role for Canada within a much larger alliance. After 1945, the RCN became the best anti-submarine warfare (A/S or ASW as it is now known) navy in the world as part of the North Atlantic Treaty Organization (NATO). But it was not an easy or direct path.

In 1939, the RCN expected submarines to be a manageable problem. As Chief of the Naval Staff, Commodore Percy Nelles observed in 1937, “If international law is complied with, Submarine attack should not prove serious.” However, should submariners again resort to unrestricted attacks, Nelles felt that “the means of combating the Submarines are considered to have so advanced that by employing a system of convoy and utilizing Air Forces, losses to Submarines would be very great and might compel the enemy to give up this form of attack.”


Submarines: a manageable problem?

Convoys and airpower had reduced the effectiveness of the submarine in 1917–18, but the optimism of naval officers about the submarine problem was fired by the perfection of “asdic” (now called sonar). This active “pinging” acoustic locating device allowed warships to attack submerged targets effectively. It had never been used extensively under operational conditions, but interwar trials and training suggested that few subs — expected to operate inshore and submerged — would now escape the deadly combination of asdic and depth charges.

Sinking of Athena and the start of the convoys

Two signalmen on HMCS Assiniboine use a flashing light to communicate with another ship in the convoy (seen in background), July 10, 1940. (DND photo H-96)

SS Athenia arrives in Montreal, circa 1932. (Library and Archives Canada photo PA-056818)

When the liner SS Athenia was sunk by U-30 on September 3, 1939, the day the war began, it was assumed that the Germans had resumed an unrestricted submarine campaign against Allied shipping. Convoys were instituted immediately, and the first to sail from Halifax, HX-1, left with an escort of HMC Ships Saguenay and St. Laurent on September 16. The destroyers protected the convoy from submarines inshore. Once HX-1 was well out to sea, larger vessels arrived to shield it from surface raiders — a threat which lingered well into 1941.The primary function of the convoy system was safe and timely arrival of the ships, and the object of its passage was avoidance of the enemy. At times, special intelligence (called Ultra), provided by breaking the German operational codes for the North Atlantic, permitted highly effective routing. But the subs could not always be avoided and the convoy system provided the focal point for much of the RCN’s war with the U-boats.


There was little in the first year of the war to suggest that submarines were a major issue. When the Canadian Navy ordered its initial wartime shipbuilding program in early 1940, its main vessel — the corvette — was completed as a jack-of-all-trades, but would prove to be master of none. This included complete minesweeping equipment, a single magnetic compass and the most basic of asdic, the type 123A. In 1940 none of this seemed to matter.

New U-boat tactic: ‘Wolf Pack’

DND photo RE85-1474

Two Type VIIC German submarines (U-boats) prepare to leave port.

Under operational conditions submarines proved remarkably difficult to locate and destroy, but what really confounded the Allies was the adoption of new tactics by Germany’s U-boats. In the late summer of 1940, the U-boats, operating from new bases in France, began to employ “pack attacks” on Allied convoys on the high seas. The deployment of U-boats into a long patrol line solved the problem of locating convoys in the vastness of the ocean, while the U-boats themselves attacked the convoy on the surface at night like motor torpedo boats — submerging only to escape Allied forces. What followed was the U-boats’ first “Happy Time,” when they roamed the Atlantic with impunity, overwhelming the tiny escorts of transatlantic convoys and creating a generation of U-boat aces.

The RCN participated modestly in this early phase. The bulk of the navy’s destroyers were already overseas guarding Britain against invasion. These destroyers soon joined escort forces for convoys in the Western Approaches. It was during these operations that HMCS Ottawa shared in the destruction of the Italian submarine Faa’ di Bruno on November 6 — the first time the RCN destroyed an enemy at sea.


Packs move westward, RCN fills the gap

What ultimately drew the whole RCN into the war against the U-boats was the extension of pack attacks westward. By the spring of 1941, the British had pushed anti-submarine escort of transatlantic convoys to south of Iceland, leaving a gap between there and the limits of RCN escorts on the Grand Banks. In May 1941, the British asked them to fill that gap in transatlantic anti-submarine escort of convoys. As a result, the Newfoundland Escort Force (NEF) was born and with it the commencement of the RCN’s war on U-boats.

The reputation of the RCN in this war depends on the success or failure of the NEF... (Newfoundland Escort Force)

— Commodore L. W. Murray, RCN, Flag Officer, Newfoundland Force, October 1941

The Corvette: the RCN’s jack of all trades

Two explosions are seen on the surface of the water from the perspective of a ship.

A depth charge attack in progress.

DND photo NP-893

A depth charge is fired from the corvette HMCS Pictou (K146).

DND photo O-753

Commander J.D. Prentice, Commanding Officer, on the bridge of the corvette HMCS Chambly (K116) at sea, May 24, 1941.

The burden of this new role fell on the RCN’s corvettes, those jacks-of-all-trades built for local work. In the spring of 1941, their great value lay in seakeeping and operational range, thereby allowing the convoy system to be completed. The keys to effective trade defence were evasive routing based on good intelligence — and the British battle fleet, which sank Bismarck in May. The close escort only fought if the system failed. So in 1941, using newly commissioned and ill-equipped Canadian corvettes with poorly trained crews in the mid-ocean was a fair risk.

Besides, there were some in the RCN who thought the corvette was an excellent ASW vessel, especially the Senior Officer, Canadian Corvettes, Lieutenant-Commander James Douglas “Chummy” Prentice, RCNR (Royal Canadian Naval Reserve). A Canadian who had retired from the Royal Navy in 1934, Prentice thought that the nimble and highly manoeuvrable corvette was more than a match for the U-boat, and he taught their crews to launch “quick attacks.” These called for a steady 12-knot speed during both the search and the final depth charge attack. This allowed contact to be maintained until the last possible moment, and eliminated the sudden burst of speed in the final attack run that would alert the U-boat. Enthusiasm for attacking and sinking U-boats were the hallmarks of Prentice’s training schemes throughout the war, and it may account for the success of Canadian corvettes in destroying U-boats.

The challenges: leadership, intel, teamwork, communications

DND photo H-1293

View of convoy from HMCS St. Croix (I81), March 1941. On September 20, 1943, while part of Escort Group 9, HMCS St. Croix would be sunk by a torpedo from U-305.

However, what was wanted from 1941 to 1943 was less the ability to sink U-boats than skill at defending convoys, and equipment shortages made this task especially difficult. Good convoy defence required good tactical intelligence, excellent leadership and teamwork, and effective communications. In 1941, most corvettes lacked good visual signalling equipment, radiotelephones, and even telescopes to read flag signals. Escort groups were often ad hoc, leadership was inconsistent, and group training non-existent — because no permanent group training establishment existed.

These problems were manifest in all the operations of the NEF, especially in the battle for SC-42 in September 1941.The slow eastbound convoy was escorted by the destroyer HMCS Skeena and three corvettes, with support from now-Commander Prentice’s training group, Chambly and Moose Jaw. During the initial confused night action of September 8-9, when seven ships were lost, the escort caught only glimpses of the attackers. When Kenogami fired its four-inch gun at a U-boat, the blast left everyone temporarily night-blind and the sub escaped. Meanwhile, Skeena pursued a U-boat inside the convoy just as the convoy started an emergency turn. While Skeena swerved to avoid collisions, the U-boat raced by it on an opposite course drawing fire from every gun within range. Both Skeena and the U-boat escaped unharmed.

U-501: the RCN gets its first U-boat

DND photo NF-722

Mate A.F. Pickard and Chief Engine Room Artificer W. Spence, St. John's, Newfoundland, 1942. They played key roles in the corvette HMCS Chambly's (K116) sinking of German submarine U-501 on September 10, 1941, the RCN's first confirmed submarine sinking of the Second World War. For their actions, Pickard received a Mention in Despatches and Spence received a Distinguished Service Medal.

Canadian fortunes were redeemed the next night when Prentice’s Chambly blew U-501 to the surface right in front of Moose Jaw. When Moose Jaw ran alongside the submarine, the U-boat’s captain blithely stepped from his conning tower to the corvette’s fo’c’sle. Then U-501 got underway. Moose Jaw eventually rammed it, then used its guns to keep the Germans from manning their armament. Most of the crew was captured before the U-boat sank: U-501 was the RCN’s first confirmed U-boat kill, and its first single-handed destruction of an enemy warship.

DND photo H-2252

Radar set on HMCS Camrose (K154), December 1941.

In the end, 16 merchant ships were lost from SC-42. In reaction, the RCN increased the size of escort groups, and scrambled to acquire new equipment like radiotelephones and radar. But this all took time. Only 15 early model radars were fitted to Canadian corvettes before the end of the year, and communications remained a major impediment: in mid-October, Shediac missed a flag signal ordering a change in convoy course and the next morning found itself alone at sea. Through the fall of 1941, NEF operations remained plagued by poor equipment, too few destroyers and escort group commanders, no training, and an operational cycle between Newfoundland and Iceland that was unbearable as winter set in. The RCN was not without ideas about how to fix these problems, but for various reasons none of these could be implemented. What saved the struggling NEF was the sudden transformation of the war itself on December 7, 1941.

DND photo Z-1664

A stricken tanker ablaze and sinking after a U-boat attack. Tankers were prized targets and strategically placed in the centre of a convoy for maximum protection, but a skillful and daring U-boat captain could strike even at the heart of a convoy.


America enters the war, U-boats stalk the U.S. East Coast

The entry of the United States into the war opened-up a vast new theatre for enemy operations, and by the end of January 1942, U-boats were probing the U.S. coast. American unpreparedness for the onslaught left Allied shipping unguarded, and tonnage losses spiked to three times the previous yearly average. Canada was spared much of this calamity because of the rapid introduction of convoys along the East Coast, such that the RCN even ran oil tanker convoys to South America through the carnage without loss.

But the expansion of the war in 1942 resulted in two defeats for the RCN that year. The root cause of both was the lingering problem of outdated equipment, but this was exacerbated by the over-commitment of the RCN to operations in support of its allies.

War comes to the Gulf of St. Lawrence

The first area to feel this inflexibility was the Gulf of St. Lawrence. The Canadian Navy had long anticipated U-boat attacks in the Gulf. The moment came in May, when U-553 sank the steamers Nicoya and Leto between Gaspé and Anticosti Island. By the time U-132 arrived in the St. Lawrence River in early July, traffic was moving in convoys. But in the “slot” between Father Point and Cap Gaspé the river confined their movements to an easily intercepted route. U-132 discovered this on the bright moonlit summer night of the 6 – 7 of July, not far from Rimouski, when it sank three ships from the Quebec-Sidney convoy QS-15.The escorting Bangor-class Drummondville caught U-132 on the surface and tried to ram it; however, the U-boat crash-dived successfully. Drummondville then bracketed the sub with depth charges, inflicting serious damage, but no asdic contact was obtained.

The real damage was done by U-517 and U-165. In the early hours of August 27, in the northern gulf, U-517 sank the American troopship Chatham (only 13 of the 562 passengers and crew were lost), while U-165 attacked the main body of the convoy sinking one ship and leaving another foundering to be sunk by U-517.

DND photo CT-248

The corvette HMCS Weyburn (K173).

DND photo H-1445

The armed yacht HMCS Raccoon (S14) on patrol, April 1941.

U-517 then escaped destruction when it entered Forteau Bay and ran afoul of the corvette Weyburn, which was unable to get an asdic contact. Those same poor acoustic conditions saved U-517 several days later after it attacked the little Quebec-Labrador convoy NL-6. Weyburn stumbled onto U-517 as it took aim at the Donald Stewart, driving the sub underwater just as the torpedoes were fired. As the steamer sank, Weyburn looked in vain for the U-boat. Tony German, a junior officer on Weyburn’s bridge, later recalled, “It is a fact that Weyburn didn’t get a sniff of him on asdic although we’d seen him twice, as large as life.”1

In September, U-517 and U-165 moved into the St. Lawrence River and let the convoys come to them. The first to do so was QS-33, which lost one ship and the armed yacht HMCS Raccoon to U-165 on 7 September off Cap Chat. The next day, U-517 sank three ships from the convoy off Cap Gaspé. German radio gloated over the victory, describing Canada’s escort fleet as third rate. Four days later, U-517 destroyed the corvette Charlottetown in broad daylight off Cap Gaspé. Then on the September 15, U-517 attacked SQ-36 by using the eastward flow of the river and the forward motion of the convoy to drift silently down on its victims in the darkness, sinking two ships. U-165, informed of the convoy’s progress, later hit three ships in a submerged daylight attack.

No naval counterattacks were effective against these two intrepid submariners. In many instances the escorts were right on top of U-boats and watched them submerge. And yet the searching asdics failed to penetrate the complex water layers. As one German U-boat captain later observed, once down into the Gulf through the 15-metre depth “layer” they were as “safe as in the bosom of Abraham.”2

Gulf closes to shipping

The Canadian Navy had to admit defeat and the government closed the Gulf to oceanic shipping in September 1942.Actual losses to Gulf shipping were negligible: for the QS-SQ series only 1.2 percent. Moreover, the decision was made late in the shipping season and other ports could handle the traffic. Nonetheless, both the navy and the government took intense public criticism for their inability to keep the nation’s main artery open in the face of enemy attack.

Perhaps for that reason, problems in the navy’s other major effort, in the mid-ocean, remained a secret for 40 years. The elimination of Iceland as an escort relay point in February (to free escorts for elsewhere) forced convoys to travel a predictable route across the Atlantic by the spring of 1942.The advantage for the RCN was that its four Newfoundland- based escort groups gained access to excellent facilities in Northern Ireland, including training. When the U-boat packs returned to the mid-ocean briefly in May, to see what was going on, they easily found Canadian escorted convoys but did not find them easy targets.

Lack of modern radar: a major problem

DND photo H-2038

Radar aerial (SW-1C and SW-2CQ) on foremast of HMCS Drumheller (K167), Halifax, November 1941.

Men stand on a ship’s bow.

The ex-USN 'four-stackers' were not the best anti-submarine warfare platforms, but they were good enough for the critical years of 1940–41. Here St. Croix returns to Halifax after a harsh winter crossing.

Nonetheless, serious equipment shortfalls remained, especially the lack of modern radar. Although the RCN was adapting to 1.5-metre sets known as the SW-1C, the British were already fitting the shorter wavelength (and hence more precise) 10-centimetre radar, the type 271. It could detect small targets on the sea at considerable ranges. The RCN was also short of destroyers and shipboard high frequency direction finding (HF/DF) radio-interception gear. Destroyers provided escorts with the speed needed to “put down” shadowing U-boats, forcing them to submerge and so drive off the enemy. Only the RCN’s pre-war River class and the ex-American “four-stacker” St. Croix class had the range to operate in the mid-ocean. In theory, the British made up for the shortfall of destroyers in Canadian groups. But the RN destroyers assigned were often mechanically unreliable and in the fall of 1942, Canadian mid-ocean groups frequently sailed with only one destroyer.

The importance of destroyers was enhanced if their sweeps were directed by HF/DF. HF/DF could fix the direction and rough distance of a U-boat wireless transmission, and two sets could fix the sub’s location by triangulation. If this was done early and well enough, destroyer sweeps might help the convoy escape entirely. At the least, HF/DF-directed sweeps reduced the number of U-boats the escort had to fight. In 1942 the only Canadian ship fitted with HF/DF was Restigouche.

Western Support Force established

The RCN also understood the need to reinforce threatened convoys, especially in the fog shrouded waters of the Grand Banks. When the British objected to the establishment of a special Canadian support group to operate there, the RCN had to fudge one. In April 1942, “Chummy” Prentice’s training group was re-established and during the next four months, he trained over a score of corvettes and supported nearly as many convoys east of Newfoundland. When his group dissolved in August due to increased operational commitments, the Americans and British soon established the “Western Support Force” to fill the need.

There was no question that RCN escorted convoys needed all the help they could get in late 1942, for they were still slaved to slow convoys. In the last half of 1942, the RCN escorted 14 out of 24 slow eastbound convoys, while the RN protected the fast HX series. The British escorted more than their share of the slow westbound convoys (17 out of 21), but westbound speeds were nominal: all ships steaming in ballast against prevailing winds were slow. This meant that Canadian escorted convoys — roughly 35 percent of the traffic — were more easily intercepted, more easily attacked, and spent longer in the danger area.

DND photo CT-273

HMCS Restigouche (H00) departs Halifax May 15, 1942, fitted with her High Frequency Directing Finding (HF/DF) equipment.

Mid-ocean attacks start

Attacks against convoys in the mid-ocean began in earnest in early June, when ONS-100, the hundredth slow convoy returning from the United Kingdom to Halifax, was attacked while escorted by C-1.The next slow convoy, ONS-102, escorted by the “American” group A-3 of two U.S. Coast Guard cutters, a USN destroyer, the Canadian destroyer Restigouche, and three RCN corvettes, reinforced by Prentice’s training group of Chambly and Orillia, fared much better. In one day alone Restigouche used its HF/DF set to locate and drive off five U-boats as they made their sighting reports: two were damaged. Meanwhile, Prentice operated as distant cover and a “striking force” around ONS-102. In the end, only one daring submariner slipped into the convoy, sinking one ship.

Some RCN successes in convoy battles

These battles confirmed the need for modern equipment, but there was little the RCN could do to acquire it before the year ended. Moreover, convoy battles in July and August were not without success for the RCN. In the battle around the fast UK to New York convoy ON-113 at the end of July two ships were lost, but St. Croix sank U-90. In the battle for ON-115 a week later, C-3 fought the “wolf pack” to a stalemate for most of the passage. In the absence of HF/DF, the group used its medium frequency direction finders (fitted for navigational purposes) to locate the MF homing beacons of shadowing U-boats. It was only partially successful, and it may simply have been the aggressive patrolling by Saguenay and Skeena during the transit that kept the pack at bay. Sweeps also led to the destruction of U-558 on July 31 by Skeena and the corvette Wetaskiwin.

DND photo O-693-A

HMCS Orillia (K119) as seen from the deck of HMCS Chambly (K116) in the fog of the North Atlantic.

Naval personnel pose for a picture on a ship tied to a dock.

Rear-Admiral L.W. Murray, Flag Officer Newfoundland, greets the crew of the destroyer Assiniboine at St. John’s after their sinking of U-210 on August 6, 1942; the ship’s captain, Lieutenant- Commander John Stubbs (right), would be lost with his next ship, Athabaskan.

ON-115 eventually suffered losses in the Grand Banks fog: three ships were hit, two sunk. Had the rump of C-3 been fitted with modern radar they could have turned the poor visibility to advantage. The corvette Sackville had three close encounters with U-boats on the night of July 31–August 1. At the time it was believed it killed one and seriously damaged another. But none was sunk. Even British staff officers concluded afterward, “Sackville’s two [sic, actually three] U-boats would have been a gift if it had been fitted with RDF [radar] type 271.”3

Two more U-boat kills followed that summer. The most dramatic was Assiniboine’s memorable battle with U-210 in the fog around SC-94 in August after a wild hour-long running gun battle. While Assiniboine tried to ram and the U-boat tried to steady on course long enough to dive, they traded gunfire. U-210’s conning tower was riddled with holes and littered with dead; Assiniboine’s upper decks and bridge were cut-up by German 40mm fire, and small fires started in its superstructure. Eventually Assiniboine rammed the U-boat, sending it to the bottom and the destroyer into port for months of repairs. The British corvette Dianthus helped even the score around SC-94 by ramming and sinking another sub.

The RCN killed one more U-boat in the summer of 1942 (but it was not credited until 1982), when Morden sank U-756 in the battle for SC-97 on September 1. That marked the end of a successful summer for Canadians on the North Atlantic Run. Of the five U-boats destroyed in the mid-ocean since May, Canadians sank four. One can only wonder at what the C groups might have accomplished had they been properly equipped. But when they stopped sinking U-boats, the RCN mid-ocean effort came to be judged by its ability — or inability — to defend convoys.

More losses, not enough destroyers

The crisis began in September with the passage of ONS-127, during which aggressive sweeps by St. Croix and Ottawa could not prevent the loss of seven ships and Ottawa itself with heavy loss of life. Canadians congratulated the escort of ONS-127 for a difficult job well done, blaming the losses directly on the lack of modern radar. Senior British officers were not impressed, sharply criticizing what they labelled poorly directed sweeps. The British had long suspected that the Canadians were aggressive but misguided and ONS-127 seemed to confirm that.

DND photo H-200

The destroyer HMCS Ottawa (H60).

With the loss of Ottawa, and with Assiniboine and St. Laurent in refit, the RCN was now down to one destroyer for each of its four mid-ocean groups. While the RCN looked for ways of acquiring more escort destroyers, it finally removed the bureaucratic hurdles to fitting modern equipment in British ports and hoped that the British destroyers assigned to the C groups were able to steam. And to make matters even worse, the Germans now had a radar detector to warn of first generation — metric wavelength — sets. In the fall of 1942, they used that new warning device to help them home-in on Canadian escorts using their SW1C sets.

Men and women in uniform work diligently in the combined operations room.

The RCN-RCAF combined operations room at St. John’s.

In contrast to the struggling Canadians, the British groups in the mid-ocean sank U- boats and put up effective radar barriers around their convoys. In the most serious British battle of the fall, for SC-104 in mid-October, eight losses to the convoy were balanced by two U-boat kills by RN destroyers. If Canadian ships could no longer sink U-boats, they must at least protect shipping. The tragic passage of SC-107 in early November suggested that they could no longer do that, either.

SC-107, escorted by Restigouche and six corvettes, was intercepted while still west of Cape Race. Seventeen U-boats were directed to attack. One was sunk by the RCAF early in the battle, while Restigouche used its HF/DF to help drive off shadowers. But with only one destroyer, and with only Restigouche and the British corvette Celandine with modern radar, the escort was overwhelmed. Eight ships went down in the first furious night of battle; seven more followed over the next week. No U-boats were sunk by the naval escort. It was a devastating blow to Canadian prestige and morale.

In contrast, ONS-144 coming the other way a week later and defended by only six corvettes, five Norwegian and one British, of group B-6 was also beset by a large pack. Fortunately, all the escorts carried type 271 radar and by forming a tight barrier around the convoy they fought it through with only six ships lost.

DND photo NF-1377

Signalmen on HMCS Kitchener communicate with another ship in a convoy en route to Liverpool, October 1942.

Mid-ocean now the only convoy route to Britain

Quite apart from Canadian shortcomings, the British were anxious about the mid-ocean by November for other reasons. The landings in North Africa on November 8 resulted in the suspension of the eastern Atlantic convoys, making the mid-ocean the only way in or out of Britain. Moreover, much of the shipping lost in 1942 was British or British chartered, and the North African campaign strained what remained.

By November the Allies were also operating in the Atlantic without the benefit of Ultra intelligence. Since the previous February, Allied cryptanalysts had been unable to read the signals of Atlantic U-boats. Through most of 1942, with the U-boats attacking inshore, this was not a serious problem. However, by late 1942, the U-boats began to concentrate in the mid-ocean again. The decisive battle of the Atlantic war was looming and any weakness in Allied escort forces had potentially disastrous consequences.

Inadequate training, maintenance, leadership, equipment

SC-107 pointed to the Canadians as the weak link in the mid-ocean. Training, maintenance, leadership, and equipment all seemed to be inadequate. Even the Americans confided to the British their concerns about the ability of the Canadians. Obscure warnings about “fairly drastic” measures to sort out the mid-ocean reached Ottawa in early December. The RCN was aware of the need for action, too. In November, Saguenay was damaged in a collision and St. Croix went into refit, leaving Canadian mid-ocean groups desperately short of destroyers. In early December the government appealed to the British for the loan of at least 12 escort destroyers.

The British were not convinced that destroyers were the solution. They believed that the RCN had expanded too rapidly, taken on too many tasks, was poorly trained and badly led. Something had to be done. The British solution was to get the RCN out of the embattled mid-ocean. On 17 December 1942, Winston Churchill made a formal request to the Canadian government asking that the C groups be withdrawn.

DND photo R-701

Vice-Admiral Percy Nelles, Chief of the Naval Staff, arrives at Naval Service Headquarters in Ottawa.

The Canadian naval staff rejected the British claims. Equipment shortages were crucial, as was the unreliability of the RN destroyers assigned to Canadian groups, and the burden of escorting slow convoys. Even Lieutenant-Commander P.M. Bliss, RN, recently arrived in Ottawa from St. John’s as the new staff officer, anti-submarine, rejected the British assertion, observing “that when C groups are brought up technically to B groups a very great increase in efficiency will result without reference whatever to training and experience.”4

Bliss was right. However, events at sea undermined the Canadian case. In late December, ONS-154, escorted by C-1, was routed through the widest portion of the air gap, battered by the tail end of a hurricane, and beset by 20 U-boats. The escort had much new equipment aboard, but the radars and HF/DF sets were not yet calibrated and the assigned British destroyer failed to show. C-1 fought blind, holding the U-boats to a draw for the first two days, sinking U-356 in the process (not awarded until after the war).Then the defence was overwhelmed and ONS-154 lost 15 ships, with no apparent retribution exacted upon the enemy.

Prime Ministers Winston Churchill and W.L. Mackenzie King leave the House of Commons, Ottawa, December 30, 1941, after Churchill’s famous ‘Some Chicken! Some Neck!’ speech to Parliament to help boost wartime resolve and morale. (Library and Archives Canada photo C-015132)


On the January 6, 1943, the Canadian Cabinet agreed to the temporary withdrawal of Canada’s mid-ocean escorts. “This is another real good turn you have done us,” Winston Churchill replied. Indeed, it was. The RCN had been driven to the brink of collapse in 1942, in the face of enormous enemy pressure. As the RN’s Monthly Anti-Submarine Report for January 1943 conceded, “The Canadians have had to bear the brunt of the U-Boat attack in the north Atlantic for the last six months, that is to say, of about half of the German U-boats operating at sea….” That they did so with a fleet manned largely by reservists who “put up a good show is immensely to their credit.” In short, during the last half of 1942 the Canadian Navy shouldered the weight of the U-boat war. Sadly, subsequent historians of the Atlantic war failed to notice.

Better weather, intelligence, air support: the keys to victory

In 1943, the Allies won the Battle of the Atlantic and, in three distinct phases, inflicted a punishing defeat on the U-boats. The RCN was not really a part of this great Allied offensive: it remained tied primarily to close escort work. In the spring of 1943, victory around the transatlantic convoys was won by a combination of better weather, improved intelligence, increased air support, and designated “support groups” that were able to hunt and kill U-boats.

DND photo R-1078

HMCS Athabaskan (G07) anchored at Plymouth, England.

The RCN had a front row seat for this offensive when its escorts returned to the mid-ocean in March and early April, but attempts by the Canadians to again field a support group did not come to fruition until late May. By then the carnage in the mid-ocean had ended and the Germans had temporarily abandoned pack attacks.

Summer Allied offensive

The Allied offensive over the summer consisted of air assaults in the Bay of Biscay, and by USN escort carriers off northwest Africa and south of the Azores. By the time EG-5 (Escort Group-5), the first RCN support group, got into the Biscay to help the air force, the battle had escalated to include surface vessels and heavy reinforcement from the German air force. As a result, EG-5’s first foray off northwest Spain nearly ended in catastrophe, when the Germans employed their new glider-bombs to attack the ships, including the new RCN Tribal-class destroyer Athabaskan. Surface ship ASW operations in the area were subsequently abandoned.

U-boats fight back: acoustic torpedoes, more anti-aircraft fire

DND photo R-529

Stoker 1st Class William Fisher, RCNVR, with Wren Jill Humphreys. Fisher was the sole survivor of HMCS St.Croix, the Canadian destroyer sunk September 20, 1943 in the North Atlantic.

Meanwhile, the second RCN support group, EG-9, arrived in the UK. Its first assignment also encountered a new weapon that effectively destroyed the group. In September, the Germans planned to blast their way back into North Atlantic convoys using increased anti-aircraft fire and a new acoustic homing torpedo. In late September, 20 U-boats equipped with this new equipment lay in wait for ONS-18/ON-202, two convoys that joined together as they approached the pack. EG-9 was sent to help.

By the time EG-9 arrived on September 20, a full battle was underway. The British frigate Lagan of C-2 already had its stern blown-off by a homing torpedo, and while conducting a sweep, St. Croix of EG-9 was struck by a homing torpedo that left it shattered. EG-9’s senior officer arrived in HMS Itchen just in time to see the second torpedo strike St. Croix, which disappeared in a towering explosion. When a torpedo detonated in Itchen’s wake, it set off to screen the rescue operation of the corvette Polyanthus. All that Itchen ever found of the corvette was wreckage and a single man clinging to it: Polyanthus, too, had been completely destroyed by a single homing torpedo. It was early the next morning before Itchen returned to pluck 100 survivors of St. Croix from the sea and headed back into the battle.

Despite intense air support and the sinking of one of the attackers, 10 U-boats remained in contact with ONS-18/ON-202 at dusk on September 22. That night, EG-9’s corvettes Morden, Chambly, and Sackville all dodged homing torpedoes, but Itchen was not so fortunate. It disappeared in a shattering blast caused by a torpedo detonating just below its magazine. Only three men survived: two from Itchen and one who had been rescued from St. Croix; Polyanthus’s lone survivor perished.

DND photo RE94-1125-5

Canadian Anti-Acoustic Torpedo (CAAT) gear.

The Germans claimed a great victory in the battle for ONS-18/ON-202, but the truth was quite different: three escorts and six merchant vessels were lost, but so were two U-boats. An RCN success of sorts in this battle was the quick response to the homing torpedo. Production of Canadian Anti-Acoustic Torpedo (CAAT) equipment began on September 21, the day after St. Croix was sunk and while the battle still raged. By the time ONS-18/0N-202’s escorts arrived in St. John’s, their new CAAT gear was waiting. Meanwhile, the final German pack assault on the transatlantic convoys fizzled out, hounded and beaten by Allied naval and air power — and watched again from the sidelines by the RCN. It was not until November that the first U-boat kill fell to an RCN support group, when Snowberry of EG-5 sank U-536.

1944: The RCN’s best year for anti-sub warfare

If 1943 was arguably the worst year of the war for RCN ASW, then 1944 was the best. The sinking of U-536 in November 1943 marked the start of a year-long period in which the Canadian Navy was second to none in finding and sinking submarines. Over the winter of 1943–44, much of the support group effort around transatlantic convoys fell to the Canadians, including EG-6, EG-9, and C-2. They did extremely well, with a concentration of successes in the open ocean in the late winter and early spring. Indeed, between the sinking of U-257 by the new River-class frigate5 Waskesiu on February 27, 1944, and the end of April, the RCN sank four out of 14 U-boats claimed by surface vessels in the North Atlantic.

A boarding party from the corvette Chilliwack comes alongside U-744, March 6, 1944.

Among these winter victories was U-744, pursued by C-2 for 32 hours on March 5-6, the second longest hunt of the war. C-2 was operating in support of HX-280 when Gatineau picked-up U-744 on asdic at a great depth. Its captain was no ordinary submariner, and attacks during the day achieved nothing. C-2 circled the U-boat that night, maintaining asdic contact and waiting for first light to renew its attacks. The next morning, the pounding began. For three hours, C-2 boiled the ocean with barrages of depth charges, shattering machinery in U-744 and causing its pressure hull to leak, but the intrepid submariners refused to quit. After a pause for several hours, and amid deteriorating weather, C-2 attacked again in the late afternoon. Then suddenly U-744 bobbed to the surface near Chilliwack. The corvette smothered the U-boat in gunfire, blowing off the sub’s anti-aircraft gun and riddling the conning tower with holes. When the firing stopped a boarding party was sent away to try to salvage the U-boat. Thirty-nine Germans were rescued, but U-744 — slowly filling with water — was torpedoed and sunk.

The sinking of U-744 was a classic deep water ASW operation of the period: a large group of ships holding a deep contact, pounding it relentlessly with masses of depth charges and hoping that a lucky attack or sheer exhaustion in the submarine would end the action. Meanwhile, British support groups, equipped with newer equipment and in some cases (like EG-2) directed by special intelligence, scored with greater ease. The net result, however, was much the same: the RCN proved to be effective U-boat hunters in the first months of 1944.

RCN helps clear the Channel for D-Day

DND photo E-5729

The new frigate HMCS Swansea (K328) part of escort group EG-9.

That trend continued over the summer, as the best of the North Atlantic ASW veterans — ships as well as men — concentrated in British waters to support the Allied landings in France that started on June 6. Besides the Channel-clearing effort, the RCN committed four support groups to this campaign. The veteran River-class destroyers were combined into groups EG-11 and -12 and assigned to work in the middle of the English Channel along with two British groups. Two groups of RCN River-class frigates, EG-6 and -9, joined three British groups to form an outer barrier to the English Channel between Brest and the south of Ireland.

Inshore: a new kind of anti-sub warfare

DND photo HS-692-4

The asdic team on duty, HMCS Cobourg (K333). Asdic is now known as sonar.

These groups faced a “new” challenge: inshore ASW in tidal waters that were often mined, and invariably strewn with shipwrecks, while under constant threat of attack by the enemy. ASW veterans soon understood that proper classification of the contact was all-important — and extremely difficult. Until they learned to anticipate the impact of tidal currents on their own movements and on water passing quickly over bottom features, it was not unusual to have reports of large boulders moving at considerable speed along the bottom. This was complicated by the unexpected tendency of U-boats to lie on the bottom when being hunted.

So learning a new form of ASW and sorting out the enemy from the background clutter became the story of the summer of 1944.The best at doing this was EG-11, which sank three U-boats, the best score of any group over the summer. EG-11’s skill owed a great deal to the tenacity, patience, and inventive genius of its officers and men. They perfected systems for classifying bottomed contacts, including profiling them using their navigational echo sounder. Snagging the contact with a grappling hook on a wire, and sliding a depth charge down the wire to “cook off” against the target achieved further “classification.” EG-11 called this “tin opening.” If the debris — especially bodies or parts thereof — was fresh and German, it was probably a sub. RN officers found this particularly distasteful, although highly effective.

Continued RCN success in anti-sub warfare

DND photo HS-343-119

Portside view of the frigate HMCS Annan (K404).

The RCN continued to enjoy success in its ASW operations in the fall of 1944, when things were generally very quiet as the Germans adjusted to the loss of bases in France. The RCN achieved a pinnacle of sorts in October, when the frigate Annan of EG-6 sank U-1006 north of the Shetlands. They had given up on an asdic contact and were miles away when Annan’s radar operator took one final peek astern and found U-1006 on the surface. The frigate raced back and sank the U-boat after a brief but fierce gun battle. U-1006 was the only U-boat sunk by the Allied navies in the North Atlantic in October 1944.

Unfortunately, none of the expertise displayed by the RCN inshore in British waters in 1944 transferred easily to Canadian waters. The area was vast by comparison, there were too few support groups in Canada, and the RCN struggled with complex inshore water conditions to the very end of the war. The U-boats therefore achieved some success off Canada in 1944, torpedoing the frigate Magog in the St. Lawrence River and the corvette Shawinigan off Port aux Basques in the fall of 1944.

1945: Victory in the Atlantic brings victory in the war

DND photo O-266-1

Survivors of the minesweeper HMCS Clayoquot (J174), torpedoed by the German submarine U-806, are rescued by the corvette HMCS Fennel (K194) off Halifax, December 24, 1944.

Worse followed that winter. U-806 sank the minesweeper Clayoquot just off Halifax on Christmas Eve, and then, in early January, U-1232 began a successful cruise off Nova Scotia. On January 4, it sank three ships near Egg Island, then attacked convoy BX-141 in the very entrance to Halifax harbour during a blizzard, sinking two ships and damaging a third. U-1232 was lining up for another shot when the frigate Ettrick ran over it by accident, smashing the conning tower, rolling the U-boat over and snagging the sub with its CAAT gear. No one in Ettrick knew what had struck it until the hull was examined in drydock and bits of U-1232 removed; the sub, however, survived. Asdic conditions had been so poor that contact could not be made on the freighter British Freedom, which lay on the bottom with its bow pointed skyward.

Apart from atrocious weather and water conditions, the bottom off Halifax was so boulder strewn that asdic echoes bounced in all directions and ships often unwittingly tracked themselves. Only constant air patrols and operations by USN forces in deep water beyond the Canadian zone provided an effective check on U-boat depredations in the RCN’s own front yard in the last winter of the war.

The situation overseas was better. RCN groups continued to sink U-boats until the end of March 1945, even if they were unable to keep up with the RN. Under pressure to crush the U-boat fleet before the war ended or Germany could deploy the radically new type- XXI and XXIII subs in large numbers, the British increasingly put their better-equipped groups in the hot spots. The key components of this very late war ASW were the latest asdic and radar. In particular, the three centimetre radar of RN Captain-class frigates could detect the snorkel masts of U-boats. So radar searches became the key to initial detection, and British groups got the high probability areas as a result. Ironically, the RCN’s last “kill” of the war, U-1003, occurred when a snorkelling U-boat collided with New Glasgow on a dark night. The U-boat was subsequently abandoned and the RCN was awarded credit.

Success in Atlantic gives RCN its postwar niche: anti-submarine warfare

Men discussing on the ship as a plane flies overhead.

An RCN crew handles the surrendered U-889 off Shelburne, Nova Scotia, as a Royal Canadian Air Force (RCAF) Canso flying boat passes overhead.

The RCN destroyed 33 enemy submarines during the war: three Italian and the rest German. It was, in the end, a very small proportion of the 1,000 U-boats sunk by the Allies between 1939 and 1945, and a very modest portion of the 500 of these claimed by naval vessels. But the real measure of the RCN’s war against the U-boats lay in the shipping safely escorted. Indeed, a huge proportion of the 25,000 ships brought safely across the Atlantic during the war moved under Canadian escort. That work was not glamorous, and it made no compelling history. However, it did make Allied victory in 1945 possible. And in the Atlantic war against submarine adversaries, the RCN found its niche for the next 50 years.

Taken from The Naval Service of Canada 1910-2010: The Centennial Story
Chapter 5: Fighting the U-Boats, 1939-45 by Marc Milner

Author: Marc Milner

1 As quoted in Michael L. Hadley, U-Boats Against Canada: German Submarines in Canadian Waters (Montreal/Kingston: McGill-Queen’s University Press, 1985), 115.

2 Hadley, 228.

3 As quoted in Marc Milner, North Atlantic Run: The Royal Canadian Navy and the Battle for the Convoys (Toronto: University of Toronto Press, 1985), 140.

4 As quoted in Milner, 199.

5 The class designation followed British usage; Canadian frigates generally were named after Canadian towns, with destroyers taking river names.

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