The Impact of German Technology on the Royal Canadian Navy in the Battle of the Atlantic

by Rob Fisher

The Royal Canadian Navy (RCN) destroyed five German U-boats in two months during the summer of 1942, after sinking only two enemy submarines in the first three years of the war. Canadian anti-submarine escorts then hit a dry spell which lasted almost four months before they sank their next U-boat. To date, this brief period of success has been thought of largely as a coincidence or something of an anomaly. Many naval historians have observed this phenomenon but no one has adequately explained the reason for this brief surge in sinkings by the Canadian Navy, or considered the implications of German technological advances for Canadian warships.

Joseph Schull's The Far Distant Ships, a popular history of the Canadian Navy during the Second World War, devoted eight pages to the "summer successes" but glossed over the period of failure, from September-December in two pages.(1) Tony German's survey history of the RCN provided more balanced treatment but offered no explanation for the downturn in the fortunes of the RCN after the summer kills.(2) Marc Milner's North Atlantic Run observed that in September the Canadian escort groups' record "of at least balancing losses with U-boat kills came to an end". But this seminal book was primarily a study of convoy and escort policy and operations rather than U-boat sinking and did not speculate on the reasons behind this turn of events. Instead, Milner demonstrated the impact the lack of U-boat kills and the heavy losses of merchant ships in Canadian-escorted convoys had on British decision-makers.(3) His following book, The U-Boat Hunters, is a study of U-boat killing, but is almost exclusively focused on the last two years of the war, 1943-1945. It does not deal with the summer and autumn of 1942 in depth.(4)

Looking at this period from the standpoint of sinking U-boats rather than convoy defence--still the escort's primary task at this stage--reveals that the period of failure from September to December 1942, when the RCN did not sink a U-boat, was in fact the anomaly, not the period of success. This challenges the conventional wisdom. The predominant factor in assessing patterns in U-boat sinking by the Canadian Navy is the degree of contact between Canadian warships and enemy submarines. This is directly related to two variables: the number of U-boats and escorts at sea, and their geographical deployment. Obviously, if there were not many U-boats at sea and they were operating in different theatres from Canadian naval forces, they would have few opportunities to sink them.

This latter scenario existed from the outbreak of war until the summer of 1941. The RCN started the war with only six destroyers and the corvette building program took some time to get on track. The U-boat fleet was also small. Still, the destroyers were deployed overseas in the thick of the action after the fall of France in June 1940. This led to the RCN's first kill--shared with HMS Harvester--in November 1940. HMCS Ottawa did not receive credit for sinking the Italian submarine Faa di Bruno until 40 years after the fact.(5) This kill was an exception. Few Canadian escorts encountered enemy submarines before the autumn of 1941. The lack of more tangible results during the first two years of the war can largely be attributed to the relatively small number of RCN warships engaged in anti-submarine warfare.

During 1941 new construction began to increase the size of the German U-boat fleet while the first corvettes increased the size of the RCN dramatically. Evasive routing based upon special intelligence kept Allied convoys safely clear of the wolf packs through much of 1941. There were few chances for the new escorts to attack and sink U-boats. However, this changed in September and October 1941 when a series of convoy battles gave the RCN corvettes their first taste of action on a large scale. The passage of convoy SC 42--though otherwise a disaster witnessing the loss of sixteen merchant ships--produced the first confirmed U-boat kill for the RCN. HMCS Chambly and Moose Jaw sank U-501 as they joined the convoy to reinforce the close escort. The sinking represented a remarkable achievement for the inexperienced corvettes but the feat was not soon duplicated: the Canadian escort groups of September and October 1941 were too small--usually only 1 destroyer and three corvettes--to hunt U-boats to a kill.(6) Furthermore, changes in the deployment of U-boats in late October 1941 kept them well clear of the RCN.

German U-boats operated mainly in the Mediterranean and Gibraltar theatres during the last two months of 1941, providing the RCN with little opportunity to atone for the defeat of SC 42 or duplicate its success in sinking U-501. Enemy submarines moved into the coastal waters of the western hemisphere in early January 1942 and operated close inshore from St John's, Newfoundland south along the US eastern seaboard to the Caribbean Sea. The U-boats preyed on the abundant independent shipping, avoiding encounters with escorts and convoys at all costs.(7) Thus, despite increasing numbers of Canadian escorts at sea, not to mention the growing U-boat fleet, the RCN had little chance to prove itself during the first half of 1942. The creation of convoys off the North American coast and in the Caribbean Sea left U-Boat Command no choice but to resume attacks on convoys. The Germans began wolf pack operations against transatlantic convoys again in July 1942 and, as well, made half-hearted attempts to attack coastal convoys.(8)

The resumption of wolf pack operations produced an almost continuous string of convoy battles between July 1942 and May 1943 when Allied forces ultimately defeated the wolf packs. The RCN destroyed five U-boats in the space of six weeks in the summer of 1942 to begin this campaign. The first kill, U-90, was by HMCS St Croix on 24 July with the westbound convoy ON 113. HMCS Skeena and Wetaskiwin destroyed U-588 one week later with convoy ON 115. HMCS Assiniboine rammed and sank U-210 with the eastbound SC 94 on 6 August. HMCS Oakville and an American aircraft sank U-94 in the Caribbean Sea on 28 August with convoy TAW 15. The fifth kill, U-756, was by HMCS Morden on 1 September with SC 97.(9) There were no patterns apparent in the five kills. The kills were made both at night and by day, by both destroyers and corvettes, and by both professional and reserve escort captains. The means of detection included eyesight, ASDIC, and radar. The means of destruction included both ramming and depth charges. The victims included both inexperienced and veteran U-boat commanders. However, all of the killers formed part of the close escort of a convoy.

After the sinking on 1 September by HMCS Morden, the RCN did not sink a single submarine for almost four months afterwards. It was not for a lack of opportunities, in contrast to the dry spell before the summer of 1942. During the autumn Canadian escort groups defended several convoys against huge wolf packs. German U-boats torpedoed eleven merchant ships from ON 127 in September and fifteen merchant ships from SC 107 in November. In addition, several minor convoy battles such as SC 100, HX 212, ON 137, and ON 139 placed the RCN at the forefront of the action. The quality of defence provided by the Canadian escort groups varied greatly from battle to battle. In some cases the escort had to abandon promising contacts after only a few attacks to protect the endangered convoy. Still, the frequent engagement with the enemy provided numerous opportunities for counter-attacks. Canadian naval escorts, however, did not sink a single U-boat until HMCS St Laurent destroyed U-356 on 27 December during the battle for ONS 154.

German U-boats torpedoed fourteen ships from ONS 154, making it another disaster for the RCN. But it was also a turning point in terms of U-boat kills, which has often been overlooked by historians because of the magnitude of the losses, and perhaps because the exact identity of the killer was not clearly known until after the war. The sinking of U-356 by St Laurent kicked off another period of success for the RCN in its boom or bust cycle of anti-submarine warfare. It was the first of six enemy submarines sunk by Canadian warships in less than three months and spelled the end of the drought. Next, HMCS Ville de Quebec destroyed U-224 on 13 January 1943 and four days later HMCS Port Arthur sank the Italian submarine Tritone. HMCS Regina followed these two quick kills by sinking another Italian submarine, the Avorio, on 8 February. HMCS St Croix and Shediac destroyed U-87 on 4 March--the second kill for St Croix--and HMCS Prescott destroyed U-163 on 13 March. The RCN did not receive credit for this last kill until long after war.(10)

Changes in the deployment of Canadian escorts affected the geographical distribution of the six U-boat kills from late December 1942 to March 1943. Only the first, on 27 December, occurred on the transatlantic convoy routes between North America and Great Britain. The assignment of sixteen RCN corvettes to Operation Torch in the Mediterranean Sea in November 1942 was the first move which shifted resources out of the North Atlantic theatre.(11) The transfer, in January and February 1943, of three of the four Canadian mid-ocean escort groups from the transatlantic convoy run to the route between Gibraltar and Great Britain furthered this shift to the eastern Atlantic and Mediterranean theatre.(12) The following five U-boat kills took place, as a result, in the Mediterranean Sea and in between Britain and Gibraltar. This change of theatre has caused many historians to view the two periods as distinct episodes where vastly different conditions prevailed and accounted for the better results in the new area. The perception was that the RCN could perform well in a secondary theatre but not in the North Atlantic where the brunt of the battle was borne. However, the change in fortunes in U-boat sinking (initiated by St Laurent) preceded the wholesale transfer to the eastern Atlantic.

The degree of enemy contact experienced by the RCN--and therefore the opportunity to sink submarines--is the first variable to be considered when comparing the autumn drought and the periods of success that preceded and followed it. It is clear that the RCN encountered the heaviest action in the autumn and the high frequency of contact with the enemy should have translated into more (or at least some) U-boat kills. The periods before and after were by no means idle, and indeed were quite active by earlier standards, but did not rival the September-December months in terms of engagement by enemy submarines. The vicious convoy battles of the drought--ON 127, SC 100, HX 212, SC 107--provided excellent opportunities to engage and destroy U-boats. The RCN failed to capitalize on them until ONS 154. Viewed in these terms, the autumn dry spell stands out as the anomaly, not the periods of success.

What happened between August and December 1942 to reduce the RCN's ability to destroy enemy submarines? Or was it just chance or bad luck? Several factors stand out as potential causes of the autumn drought. First of all, the atrocious weather in the North Atlantic in the autumn of 1942. A series of unrelenting gales swept the transatlantic convoy routes almost continuously from October to December. Rough seas played havoc with ASDIC conditions and made the RCN's outdated radar virtually useless. While the weather was abnormally bad for autumn, the winter months of the period that followed were not much better. A winter gale slowed the progress of ONS 154 but its southerly route carried it close to the Azores and more moderate weather prevailed when St Laurent sank U-356 on the night of 26/27 December. The Mediterranean climate spared the Torch corvettes and Canadian escorts on the Britain-Gibraltar run from some of the worst excesses of the North Atlantic. Still, the weather is not sufficient in itself to explain the complete failure to destroy enemy submarines between September and December 1942. Nor does it explain the revival of Canadian fortunes during the winter of 1942-1943.

Some historians have speculated that the strong performance by the Torch corvettes in January and February was brought about improved equipment--specifically type 271 radar.(13) There is no denying that it was far superior to previous Allied radars for detecting surfaced submarines. Still, this explanation is not entirely satisfactory for a number of reasons. First, type 271 radar played a role in only two of the five sinkings in the Mediterranean Sea and eastern Atlantic--that of Avorio and U-163.(14) Second, the successes of the summer of 1942 were achieved by Canadian escorts without type 271 radar. Indeed, the outdated metric radar played a role in two of the five sinkings during that summer. Thus, the presence of the type 271 radar, while it did assist in the destruction of Axis submarines in the winter of 1942-43, does not offer an explanation as to why the RCN was able to sink U-boats in the summer of 1942 but not in the autumn of 1942.

German technological developments were, perhaps, the hidden cause of the autumn drought. In August, as the RCN basked in the glory of its recent successes, U-Boat Command acquired the first prototypes of the Funkmessbeobachtung 1 (FuMB 1) radar detector.(15) The Germans commonly called it Metox, after its French manufacturer. It contained French, German, and even American parts. In addition to the search receiver, it included a wooden aerial in the shape of a cross, known as the "southern cross" or "Biscay cross". The aerial had a horizontal and a vertical antenna and had to be detached and taken below before submerging. FuMB 1 intercepted radar transmissions from both air and surface escorts on wavelengths between 1.25 and 2.5 metres.(16) Thus, Allied radar types which used wavelengths of 1.4 and 1.5 metres--such as the Canadian naval radars SW1C and SW2C, British naval type 286, and the airborne ASV Mark II--were vulnerable to Metox. However, it could not detect the 9.7 centimetre transmissions produced by newer British naval type 271 radar.(17)

The introduction of the radar detector gave U-boats an advantage over Canadian escorts which they did not enjoy over British escorts. During the summer of 1942 most Canadian escorts had SW1C or SW2C radar, modifications of the type 286, and a few had the type 286 itself. Most British escorts already had the superior type 271 radar which could not be detected by FuMB 1(18). In addition to being vulnerable to Metox, the older metric radar had a poor sense of discrimination between objects on the surface and waves. It could detect a trimmed-down submarine at ranges of 1.0 to 1.5 miles in good conditions.(19) Anything approaching rough seas, however, made metric radar useless except for station-keeping. The superior type 271 radar had a much sharper sense of discrimination than metric radar. Type 271 could pick up a submarine at ranges of 3.5 miles or more in optimum conditions.(20) Only four Canadian corvettes had type 271 radar by September 1942; no destroyers had it.(21)

The Germans pressed FuMB into service quickly. Most of the submarines sailing from the French bases in September carried it and German and Norwegian ports also had supplies for installation by the end of the month. By October virtually all of the German U-boat fleet sailed with Metox.(22) The search receiver was primitive, it did not give the bearing or range of a contact, it only warned that radar was in operation nearby. Experienced operators, however, could make rough estimates of range and bearing based on signal strength and the rotation of the aerial.(23) FuMB could intercept airborne radar signals from distances up to 30 miles, well in excess of the 5-10 mile range of ASV Mark II. Its effective range against shipborne radar seems to have been in the neighbourhood of 6-10 miles which still offered a significant advantage over the very limited ranges achieved by Allied shipborne metric radar.(24)

The obsolescence of the search receiver relative to British surface radar type 271 has had the effect that most historians of the war at sea have discounted its effectiveness, except against Allied aircraft.(25) The similar tendency (though changing) to minimize or ignore the role played by the Royal Canadian Navy in the Battle of the Atlantic has caused historians to overlook the impact of Metox on the performance of Canadian warships. FuMB gave the U-boat ample warning of the approach of a Canadian escort in the autumn of 1942. In effect, in the deadly game of cat and mouse between the escorts and the U-boats, the cats had been belled. The RCN's string of summer successes came to an abrupt end with the advent of Metox. None of the Canadian escorts which sank U-boats in the summer of 1942 had been fitted with type 271 radar. From September 1942 on, only RCN escorts with centimetric radar would destroy enemy submarines.

It is often stated that U-boats did not rig Metox during convoy operations because of the need to take down the aerial quickly before crash diving.(26) Indeed, German prisoners of war possibly gave Allied interrogators this impression.(27) While this may be true of a later period, and of some German captains at this time, it is clear from war diaries that most of them used the search receiver in the midst of convoy battles during the autumn of 1942. Some examples of the performance of FuMB against Canadian escort groups during the convoy battles of September-December 1942 will illustrate its impact. It first seems to have been used against the RCN with success on 18 September, just a few weeks after the sinking of U-756. On that day U-599 made the initial contact with SC 100, escorted by the Canadian and American warships of escort group A3 (the American ships did not have centimetric radar either). The U-boat sighted the convoy and made a contact report which referred to the detection of "additional radars to the Northeast". The boat's war diary has not survived so no further details are available. Some of the other U-boats in the wolf pack had FuMB and used it during the battle around SC 100 but it does not seem to have played a dominant role. Most of the pack had been at sea since August and had not yet had the equipment installed. Still, they sank five merchant ships from SC 100, without the loss of a U-boat.(28)

During the operation against ONS 137, escorted by escort group C4, U-258 used FuMB to avoid surface escorts on 16 and 17 October. U-71 made a Metox detection on the 1.4 metre wavelength on the seventeenth in visibility of only 200 metres. The sub crash dived where it heard hydrophone effect and ASDIC noises but was not detected. U-437 evaded attack on 19 October thanks to its search receiver. The wolf pack, however, sank only two merchant ships from ONS 137.(29) The Germans made even greater use of FuMB in the operation against HX 212 in late October. By this time most, if not all, of the subs operating in the North Atlantic had the search receiver. U-575 detected an escort on 27 October and took evasive action. U-602 even used Metox to maintain contact with an escort in conditions of poor visibility. During the night of 28/29 October U-624's search receiver measured the range of an escort as 1,500 metres, again in poor visibility. The high seas made the escort's radar useless, except to the U-boat which penetrated the screen and torpedoed the SS Pan New York, a large tanker. The wolf pack sank six merchant ships from HX 212, under combined Canadian and American escort, again without suffering any losses.(30)

The Germans also found FuMB invaluable during the large wolf pack operation against SC 107 in early November. Canadian escort group C4 failed to exact retribution for the fifteen merchant ships torpedoed by the U-boats. The experience of U-71 during the night of 2/3 November shows the value of FuMB in evading a surface escort equipped with metric radar. The war diary reads: "Surface detection 142 cm. Horizontal. Initially this was a very audible constant oscillating sound. It was repeated at irregular intervals....Dived when signal was loud and constant. Subsequently heard rapidly moving ASDIC noises and listening noises". U-71 escaped without being detected or attacked. During the following night, while being driven off by an escort, the captain of the same U-boat wrote in his war diary: "Brought FuMB on to the bridge to establish whether radar detection signals were present. Two detections on 142 and 143 cm horizontal which commenced and then decreased following which there was a steady, fairly loud signal for ten seconds. Range is 3-4 n[autical ]m[iles]. The searching units appear to still be fairly inexperienced. Sent FuMB back down below when the visibility improved". Afterwards U-71 slipped past the screen for an unsuccessful attack.(31)

The pack used its Metox to good effect to avoid detection by the surface escort. U-571 intercepted three surface escort radars during the night of 1/2 November. The following night, in visibility which varied between 500 and 1,000 metres because of fog and rain, the boat received signals on her FuMB which grew steadily louder. U-571's war diary reads: attempted "to open out on the port side at half speed and on course 020 but in this process the signals become screamingly loud (they can be heard from the listening room as far as the bow compartment and the control room) and the signal is joined by a second and then by a third one which can clearly be differentiated by their different notes. I conclude from this that I was on the starboard bow of the convoy and that I am now passing close ahead on my course of 020. The visibility does not increase more than 1,000 m[etres]".(32) The sensors available to C4--metric radar and eyesight--had little hope of detecting the U-boat in the prevailing rough seas and poor visibility. These conditions would not have been such a problem for type 271 radar. It possibly would have detected the U-boat long before the Germans sighted the escort--rough weather trials showed that 271 radar could pick up a surfaced sub at 2.1 miles or more--providing its bearing and range.(33)

Other U-boats also used FuMB to detect surface escorts and avoid attack during the battle for SC 107.(34) Still, the search receiver did not have the dominant role it might have had if it had been more reliable. Almost one-half of the members of the wolf pack reported that their FuMB was unserviceable or had broken down at some point during the action.(35) The captain of U-704 suspected that he had been detected by radar when an escort forced him off the convoy on 2 November. He complained that the FuMB was unserviceable, implying that he would have been using it to guard against surprise if it had been in working order.(36) In spite of its poor reliability (something metric radar suffered from as well), it is clear that Metox greatly assisted a number of U-boats in evading detection by surface escorts during the battle, especially at night or in conditions of poor visibility. The battle was not a complete failure for Canada, however, RCAF aircraft (not using radar) sank two U-boats in daylight attacks.(37)

The Germans faced a different outcome two weeks later when they engaged convoy ONS 144. All of the British and Norwegian escorts had type 271 radar and used it to intercept U-boats time and again as they closed to attack. Escort group B6's solid defence held the losses to five merchant ships and one corvette. The failure of Metox to give warning of surface radar in this operation alarmed the U-boat captains who had taken part in the successful operation against SC 107. When escorts arrived overhead after U-521 submerged during the night of 15/16 November to listen with the hydrophones, the German captain observed: "Nothing had been heard on FuMB. Despite this I suspect radar detection or measurement as it cannot be considered probable that the escorts would steer such courses randomly but rather would only do so when something had been detected".(38) Two nights later, an escort suddenly closed U-522 which could not possibly have been sighted by the Allied warship in the prevailing conditions. The captain, Herbert Schneider, entered in the war diary: "Suspect radar detection. Turn away and rig FuMB. Nothing to be heard in this device". Similar incidents of detection led Schneider to conclude after the battle that "The escort force of this last convoy was more experienced and more difficult to prevail against than that of the previous convoy [SC 107]". He attributed this to the "difference between British and American escort forces". The perceptive submariner was close to the mark, but of course it was the difference between British and Canadian escorts. American escorts, if they had been present in larger numbers at this stage of the Battle of the Atlantic, would have suffered a similar fate to the Canadians: their ships also did not yet have centimetric radar. Finally, Schneider considered that the lack of warning provided by Metox for these incidents suggested that the detections were not made by radar. He speculated that Allied escorts had some new device--perhaps infra-red detection--for locating U-boats on the surface.(39)

In the battle for SC 104 a month earlier, this same British and Norwegian escort group had destroyed two enemy subs in return for losing eight merchant ships. The losses of merchant ships in B6's two convoy battles did not differ all that much from Canadian convoy battles of autumn 1942, but the sinking of the U-boats did.(40) Indeed, it is possible that for a brief period FuMB engendered a false sense of security in the U-boats: if radar was operating nearby surely the search receiver would detect it? There was no mention of the failure of Metox to detect the escort's radar in the U-Boat Command War Diary at this time.

Allied authorities realized by November that the Germans had developed a radar detector. Intelligence revealed that FuMB (known as the German Search Receiver or GSR to the Allies) could only detect metric radar transmissions.(41) Western Approaches Command issued a general order to that effect which escort group C3 incorporated into its standing orders. Thus, during the pursuit of SC 109 from 16-19 November, the Senior Officer, Lieutenant-Commander K.L. Dyer, RCN, ordered strict radar silence for three of his six escorts--those without centimetric radar. His move was sound because the shadower, U-43, had FuMB rigged. It made a number of detections against aircraft before the convoy moved out of the range of Newfoundland-based aircraft. Dyer considered the risk of detection by Metox greater than the chances of SW2C or type 286 radar uncovering the U-boat.(42) Later in the month, HMS Broadway, the Senior Officer of escort group C2 with ON 149, ordered HMS Sherwood not to operate her type 286 radar.(43) In effect, FuMB had neutralized metric radar and escorts equipped with it basically operated without anti-submarine radar by late November.

The fact that two of the five Canadian escorts with SC 109 actually carried type 271 radar revealed that the RCN had made some progress in fitting it. The RCN had begun to install centimetric radar in larger numbers in early November. Whereas only four RCN corvettes had it at the end of the summer, forty corvettes and destroyers had it by 22 December 1942, the lion's share of them having it installed in November and December.(44) The sixteen RCN corvettes assigned to Operation Torch received type 271 in Great Britain in preparation for the Torch convoys while the rest of the escort fleet began to fit it piecemeal in the United Kingdom, Halifax, and New York from late October on. The installation usually required two lay-overs in Britain for the mid-ocean escorts but by the end of December 1942 about 34% of Canadian corvettes and destroyers operating in the North Atlantic and western Atlantic had centimetric radar (while all of those with Operation Torch had it).(45) When C3 sailed with ONS 152 on 10 December it was probably the first Canadian escort group in which every escort had centimetric radar, and both of its destroyers had been fitted with ship-borne High Frequency/Direction Finding as well.(46)

Through the debriefing of U-boat commanders after their return to base, the Germans too had become aware of some of the limitations of Metox. During the operation against ONS 152, U-Boat Command warned the wolf pack "that the enemy uses his location gear [radar] very cautiously and when he picks up a target he gradually reduces his signal strength to mask his approach".(47) It may have conjectured this unlikely Allied tactic to explain the inability of FuMB to detect radar transmissions during the battles with the type 271 equipped escorts of B6. It is also possible, though less likely, that they had learned that some Allied escorts were observing radar silence. The Germans, however, were still unaware that the Allies had developed a centimetric radar which operated on wavelengths outside the range of Metox.(48) By this time, mid-December, a clear majority of the escorts in the Mid-Ocean Escort Force (if not a majority of Canadian escorts) had type 271 radar. In any event, the U-boats now recognized the limitations of Metox just as surface escorts realized the dangers of metric radar.

The period of the German technological advantage conferred by FuMB corresponds closely with the drought experienced by the RCN, as it does with the longer dry spell suffered by Allied aircraft equipped with metric radar. Night-time sightings by anti-submarine aircraft in the Bay of Biscay offensive tailed off in the last two weeks of September and dropped away to almost nil during October 1942. Daytime sightings also dropped off but less sharply. The Northern Transit Offensive between the Shetland Islands and Iceland also dried up at this time. Winston Churchill, Prime Minister of Great Britain, informed Harry Hopkins on 20 November that Metox "had reduced the efficiency of our day patrols in the Bay and defeated the night patrols altogether". Not until Coastal Command aircraft began to receive centimetric radar in large numbers in mid-March 1943 did the campaign revive.(49)

The RCN drought finally ended during the night of 26/27 December when HMCS St Laurent destroyed U-356. The destroyer's type 271 radar, fittingly, picked up the U-boat at a range of 2,500 yards.(50) The destruction of U-356 was the lone bright spot for the Allies in the battle for ONS 154--which witnessed the torpedoing of fourteen ships. All of the corvettes had had type 271 radar installed before the passage but were still inexperienced in its use and had no time for training before sailing. Indeed, some of the corvettes continued to use their SW1C or SW2C metric radar because the U-boats made several FuMB detections against surface escorts during the battle. U-260, the only sub in contact during the night of 27/28 December, shadowed ONS 154 in visibility of 1,500 metres through the use of Metox. The U-boat obtained a radar signal on 138 cm horizontal, turning away whenever the signal grew louder. The German captain, Hubertus Purkhold, proceeded on a steady course alongside the escort "whose approaches were announced by radar signal". He kept a distance such that the radar signal remained constant at strength 0-1, estimating the escort's range as 5,000-6,000 metres. Purkhold maintained contact for over seven hours during the night by means of FuMB and transmitted hourly homing signals and contact reports for the rest of the pack. He reported that "Radar signals were detected every 2-6 min. and were up to 30 sec. in length". During the following day U-260 held contact in thick fog through use of the hydrophones until late in the afternoon when the visibility improved and eleven other U-boats closed the convoy. That night the wolf pack torpedoed nine ships from ONS 154 in a few hours--a feat made possible by U-260's superb shadowing, and a tragedy possibly averted if the escort had not operated its metric radar.(51)

The RCN followed up the lone success of ONS 154--the sinking of U-356--by destroying five more U-boats during the winter of 1942-43, making it another period of concentrated success. The Torch corvettes accounted for three enemy submarines in January and February. HMCS Ville de Quebec, Port Arthur, and Regina had all received type 271 before taking part in Operation Torch. In any event, the two Italian submarines, Avorio and Tritone, probably did not have the search receiver. Similarly, the RCN escorts that destroyed U-87 and U-163 in March, HMCS St Croix, Shediac, and Prescott, had centimetric radar.(52)

The period that followed March, the spring and summer of 1943, proved to be another "bust" in the RCN's cycle of U-boat killing. Canadian escorts shared in the certain destruction of only one U-boat during this period when the Allies achieved a decisive victory over the wolf packs. HMCS Drumheller, a type 271-equipped corvette, shared in the sinking of U-753 on 13 May 1943 with other Allied forces. Drumheller possibly also shared in the sinking of U-338 in September 1943, but the evidence was not conclusive enough for credit to be given. The RCN's failure to take part in the heavy U-boat sinkings of the spring and summer had more to do with the deployment of its escort fleet than with its state of readiness. Allied special intelligence permitted the Canadian-escorted convoys to evade the wolf packs or meet them on favourable terms with British support groups reinforcing the close escort. The clashes that did take place did not involve RCN ships for the most part.(53)

Allied aircraft and support groups supplanted close escort groups as the prime U-boat killers during the summer of 1943. Centimetric radar enabled aircraft to take the offensive again by neutralizing Metox. Aircraft claimed most of the kills during this phase, the golden age of maritime air.(54) The RCN now needed to form support groups and/or acquire escort carriers--surface forces assigned to hunt submarines as their primary task--if it wanted to become a major U-boat killer again. Its next official kill did not come until November 1943 when the Canadian support group EG 5 destroyed U-536 to lead off yet another intensive period of U-boat killing by the RCN during the winter and spring of 1944.(55)


1. Joseph Schull, Far Distant Ships: An Official Account of Canadian Naval Operations in World War II (Ottawa: King's Printer, 1950), pp.131-41.

2. Tony German, The Sea is at Our Gates: The History of the Canadian Navy (Toronto: McClelland & Stewart, 1990), pp.124-30.

3. Marc Milner, North Atlantic Run: The Royal Canadian Navy and the Battle for the Convoys (Toronto: University of Toronto Press, 1984), p.151.

4. Marc Milner, The U-Boat Hunters: The Royal Canadian Navy and the Offensive against Germany's Submarines (Toronto: University of Toronto Press, 1994), pp.11-13.

5. R.M. Coppock to Giovanni Corsetti, 15 December 1982, Directorate of History, National Defence Headquarters (DHist), 90/437.

6. W.A.B. Douglas and Jürgen Rohwer, "The Most Thankless Task Revisited: Convoys, Escorts, and Radio Intelligence in the Western Atlantic, 1941-3", in James A. Boutilier, ed., The RCN in Retrospect, 1910-1968 (Vancouver: University of British Columbia Press, 1982), pp.193-207.

7. Befehlshaber der U-Bootes (BdU) War Diary, November-December 1941 and January-February 1942, DHist, 79/446.

8. Robert C. Fisher, "Return of the Wolf Packs: The Battle for ON 113, 23-31 July 1942", The American Neptune 56, No 1 (Winter 1996), pp.45-62.

9. Robert C. Fisher, "Axis Submarine Losses to Canadian Forces", appendix in David Bercuson and J.L. Granatstein, Dictionary of Canadian Military History (Toronto: Oxford University Press, 1992), pp.246-248.

10. Robert C. Fisher, "Axis Submarine Losses to Canadian Forces", appendix in Bercuson and Granatstein, Dictionary of Canadian Military History, pp.246-248.

11. Shawn Cafferky, "A Useful Lot, These Canadian Ships: The Royal Canadian Navy and Operation Torch, 1942-1943", The Northern Mariner (October 1993), pp.1-17.

12. Marc Milner, North Atlantic Run, pp.220-29. This withdrawal of Canadian escort groups from the mid-ocean came about because of British concerns about the level of training on Canadian ships (pp.196-7).

13. See for example G.N. Tucker, The Naval Service of Canada: Its Official History (Ottawa: King's Printer, 1952), II, p.457.

14. Shawn Cafferky, "A Useful Lot, These Canadian Ships: The Royal Canadian Navy and Operation Torch, 1942-1943", The Northern Mariner (October 1993), pp.6-12.

15. Great Britain, Ministry of Defence (Navy), The U-boat War in the Atlantic, 1939-1945 (London: Her Majesty's Stationery Office, 1989), II, pp.42-43.

16. Great Britain, Admiralty, Naval Intelligence Division, Interrogation of Survivors of U-353, pp.13-14, DHist, 80/582, Item 14. Some sources say FuMB 1 intercepted signals on wavelengths between 1.3 and 2.6 metres.

17. Derek Howse, Radar at Sea: The Royal Navy in World War II (Annapolis, MD: Naval Institute Press, 1993), pp.142-3.

18. Approximately 102 of 113 British and British-controlled corvettes (mostly Norwegian and Free French) had type 271 radar by September 1942.

19. Norman Friedman, Naval Radar (Annapolis, MD: Naval Institute Press, 1981), pp.195-6, 201-202.

20. Derek Howse, Radar at Sea, pp.116, 277-8.

21. The corvettes were HMCS Barrie, Bittersweet, Trillium, and Eyebright.

22. Great Britain, Ministry of Defence (Navy), The U-boat War in the Atlantic, II, pp.42-43; and Great Britain, Air Ministry, Air Historical Branch, The R.A.F. in Maritime War, III, p.487, DHist, 79/599, Vol 3.

23. Great Britain, Admiralty, Naval Intelligence Division, Interrogation of Survivors of U-353, pp.13-14, DHist, 80/582, Item 14.

24. Great Britain, Air Ministry, Air Historical Branch, The R.A.F. in Maritime War, III, p.487; and Great Britain, Admiralty, Naval Intelligence Division, Interrogations of Survivors of U-353 and U-517, DHist, 80/582, Items 14 and 16.

25. See for example, Stephen Roskill, The War at Sea, 1939-1945 (London: Her Majesty's Stationery Office, 1954-61), II, p.205; John Terraine, The U-Boat Wars, 1916-1945 (New York: Putnam, 1989), p.479; or Great Britain, Air Ministry, Air Historical Branch, The R.A.F. in Maritime War, III, p.487.

26. See for example, Great Britain, Air Ministry, Air Historical Branch, The R.A.F. in Maritime War, III, p.487, which makes this claim.

27. Great Britain, Admiralty, Naval Intelligence Division, Interrogations of Survivors of U-353 and U-517, DHist, 80/582, Items 14 and 16.

28. U-599, War Diary (Signals only), 18 September 1942, DHist, 83/665; and BdU War Diary, 17-18 September 1942. U-258 also used FuMB against SC 100. Two of the escorts, HMCS Trillium and HMS Nasturtium, had type 271 radar.

29. U-258, U-71, and U-437, War Diaries, 16-19 October 1942. One of the escorts, HMS Celandine, had type 271 radar.

30. U-602, U-575, and U-624, War Diaries, 27-29 October 1942.

31. U-71, War Diary, 2-4 November 1942.

32. U-571, War Diary, 1-3 November 1942.

33. Derek Howse, Radar at Sea, p.86.

34. U-84 and U-521, War Diaries, 1-4 November 1942.

35. U-89, U-132, U-438, U-454, and U-704 reported technical problems with their FuMB during the battle.

36. U-704, War Diary, 2 November 1942.

37. W.A.B. Douglas, The Creation of a National Air Force: The Official History of the Royal Canadian Air Force Volume II (Toronto: University of Toronto Press, 1986), pp.527-8.

38. U-521, War Diary, 16 November 1942.

39. U-522, War Diary, 18-19 November 1942. The possibility of Allied infra-red detection preoccupied the Germans through 1943-44.

40. It is has been generally believed that B6 also sank a U-boat, U-184, during the battle for ONS 144, but recent research has disproved this claim. The submarine radioed base hours after it was supposedly destroyed.

41. Great Britain, Air Ministry, Air Historical Branch, The R.A.F. in Maritime War, III, p.522. The RAF narrative cites a letter from Winston Churchill to Harry Hopkins on 20 November 1942 which pointed out that centimetric radar "could not be detected by the enemy device".

42. HMCS Skeena, Report of Proceedings, SC 109, 1 December 1942, National Archives of Canada (NAC), RG 24, Vol 11335, NSS 8280-SC109; and U-43, War Diary, 16-19 November 1942. HMS Winchelsea, HMCS Galt, and HMCS Wetaskiwin had type 271 radar. The two Canadian corvettes had it installed in Halifax before sailing with SC 109.

43. HMS Broadway, Report of Proceedings, ON 149, 7 December 1942, NAC, RG 24, Vol 11320, NSS 8280-ON149.

44. Commander G.A. Worth, RCN, to Chief of the Naval Staff, 24 December 1942, NAC, RG 24, Vol 6796, NSS 8375-4.

45. David Zimmerman, The Great Naval Battle of Ottawa (Toronto: University of Toronto Press, 1989), p.84. Forty of the RCN's eighty-six destroyers and corvettes carried type 271 by 24 December 1942.

46. HMCS Skeena, Sackville, and Arvida had centimetric radar installed during the lay-over between SC 109 and ONS 152.

47. BdU War Diary, 17 December 1942. See also Karl Doenitz, Memoirs: Ten Years and Twenty Days (Annapolis, MD: Naval Institute Press, 1990), pp.231-2.

48. Karl Doenitz, Memoirs: Ten Years and Twenty Days, pp.266-7, 339.

49. Great Britain, Air Ministry, Air Historical Branch, The R.A.F. in Maritime War, III, pp.487-94, 522.

50. HMCS St Laurent, Report of Proceedings, ONS 154, 3 January 1943, and HMCS St Laurent, Report of Attack on U-boat, 27 December 1942, both in NAC, RG 24, Vol 11332, NSS 8280-ONS154.

51. U-260, War Diary, 27-8 December 1942; and Jürgen Rohwer, Axis Submarine Successes, 1939-1945 (Annapolis, MD: Naval Institute Press, 1983), pp. 143-4. U-664 and U-203 also made FuMB detections during the battle.

52. See Shawn Cafferky, "A Useful Lot, These Canadian Ships: The Royal Canadian Navy and Operation Torch, 1942-1943", The Northern Mariner (October 1993), pp.1-17, for more details of these sinkings.

53. Marc Milner, The U-Boat Hunters, pp.37-39, and North Atlantic Run, pp.239-40; and R.M. Coppock, "Loss of U-338 in September 1943", DHist, 90/437.

54. See Marc Milner, The U-boat Hunters, and David Syrett, The Defeat of the German U-boats (Columbia: University of South Carolina Press, 1994) for a description of this period.

55. Marc Milner, The U-boat Hunters, pp.78-84.

The article first appeared in "The Northern Mariner", Vol. 7, No. 4 (October 1997), pp.1-13.
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This article was published on 14 May 2002.

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Books dealing with this subject include

50 North. Easton, Alan, 1980.
Battle of the Atlantic. Milner, Marc, 2002.
A Blue Water Navy. WAB Douglas, R. Sarty, M. Whitby et al., 2007.
Canada's Submariners. Perkins, J. David, 1989.
The Canadian Naval Chronicle 1939-1945. Darlington, Robert and McKee, Fraser M., 1998.
Canadian Submarine Service in Review. Perkins, J. David, 2000.
Corvettes of the Royal Canadian Navy, 1939-1945. MacPherson, Ken and Milner, Marc, 2001.
H.M.C.S.. Milne, Gilbert A., 1960.
HMCS Swansea. McKee, Fraser M., 1994.
In Peril on the Sea. Graves, Donald E., 2003.
The Longest Battle. Harbron, John D., 1993.
North Atlantic Run. Milner, Marc, 1985.
North atlantic run. Milner. Marc, 2006.
On The Triangle Run. Lamb, James B., 2000.
The Ships of Canada's Naval Forces 1918 - 1981. Macpherson, Ken and Burgess, John, 1981.
Through a Canadian Periscope. Ferguson, Julie H., 1995.
The U-Boat Hunters. Milner, Marc, 1994.
U-boats Against Canada. Hadley, Michael, 1990. (transl.)

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