CCaannaaddiiaann MMiilliittaarryy HHiissttoorryy Volume 7 Issue 3 Article 3 1998 CCoonnffrroonnttiinngg TTeecchhnnoollooggiiccaall aanndd TTaaccttiiccaall CChhaannggee:: AAlllliieedd AAnnttii-- SSuubbmmaarriinnee WWaarrffaarree iinn tthhee LLaasstt YYeeaarr ooff tthhee BBaattttllee ffoorr tthhee AAttllaannttiicc Douglas M. McLean Directorate of Maritime Concepts and Doctrine, Department of National Defence Follow this and additional works at: https://scholars.wlu.ca/cmh Part of the Military History Commons RReeccoommmmeennddeedd CCiittaattiioonn McLean, Douglas M. "Confronting Technological and Tactical Change: Allied Anti-Submarine Warfare in the Last Year of the Battle for the Atlantic." Canadian Military History 7, 3 (1998) This Article is brought to you for free and open access by Scholars Commons @ Laurier. It has been accepted for inclusion in Canadian Military History by an authorized editor of Scholars Commons @ Laurier. For more information, please contact [email protected]. McLean: Confronting Technological and Tactical Change: Allied Anti-Submar Confronting Technological and Tactical Change Allied Anti-Sub111arine Warfare in the Last Year of the Battle of the Atlantic Douglas M. McLean T he recall of German U-boat wolfpacks from Improvements in Submarine the central north Atlantic at the end of May Technology 1943 ended the most costly phase of the shipping war for the Allies. Never again would the German S omewhat paradoxically, the new challenges U -boats inflict dangerously high shipping losses. 1 to Allied ASW forces in 1944-45 were born The naval war remained bitter. nonetheless. for of their very success in the Spring of 1943. In the U-boats refused to give up. turning instead desperation. the Germans adopted new tactics. to new technology and new tactics. Right to the These featured submerged penetration of focal end, they continued to present a plausible threat areas of trade by individual boats, which then that caused concern in high Allied circles. Indeed, waited for targets of opportunity, made sudden in January 1945 the First Sea Lord of the ambushes. and then immediately executed Admiralty was moved to warn that. "The high extreme evasive manoeuvres for prolonged shipping losses which may occur during the first periods. Unlike the massed "wolfpack" attacks half of 1945 may well prejudice the maintenance against convoys which had been the hallmark of of our forces in Europe .... "2 U -boat operations in 1942-1943, these so-called "static'"1 tactics seldom caused severe losses The ensuing struggle in early 1945 led to a because U-boats spent far more time avoiding confrontation between improvised technological detection than aggressively seeking opportunities improvements and tactical changes by the U to attack. Yet their new success in avoiding boats countered by operational and tactical detection in areas where the Allies had previously adaptation produced in reply by Allied anti been able to detect and destroy them caused submarine warfare (ASW) forces. This last phase concern in some quarters of the Allied High of the battle of the Atlantic was fought out for Command. 5 As 1944 drew to a close this the most part in the confusing and difficult apprehension grew because it appeared that the shallow waters around the coasts of the United U-boats were not only mastering the art of Kingdom and off the east coast of Canada, evading antisubmarine forces but were once moving to the shores of the United States only more becoming effective in their attacks.G in the last few months of the war. This campaign provides insights into how new and unexpected The new equipment which allowed this initiatives by an enemy could be dealt with even dramatic change in U-boat tactics was the when no te~hnological solutions were readily at schnorkeJ.7 This was a comparatively simple hand. It also illustrates the difficulty that both device which provided enough air to allow U submarine and antisubmarine forces encounter boats to operate their diesel engines while when operating in the challenging environment submerged.8 Little more than a tube about as of shallow water.3 ©Canadian Military History. Volume 7, Number 3, Summer 1998, pp.23-34. 23 Published by Scholars Commons @ Laurier, 1998 1 Canadian Military History, Vol. 7 [1998], Iss. 3, Art. 3 Sleek type XXI U-boats at Lisahally. Northern Ireland, 1945. U-2582. on the lf(ft. has her sclmorkel mast raised. The submarine in the middle is U-2511. the only type XXI to undertake a wartime cruise. long as the submarin~·s periscope, the schnorkel frustratingly difficult opponent.12 Although greatly reduced a U-boat's vulnerability to shipping losses remained comparatively light, searching Allied forces because its small head schnorkel-equipped U-boats regularly prowled was far less conspicuous than the submarine's in the vicinity of the shipping routes to the conning tower. Moreover, travelling slowly and beachheads. Even when discovered these carefully, the U-boat needed to use the schnorkel submarines proved elusive targets, and. in view only three to five hours in every twenty-four.9 of the immense concentration of ASW forces. Most U-boat commanders prudently schnorkeled remarkably few were destroyed. ~~l at night to avoid visual detection of the smoke produced by the submarine's diesel engine. In In addition the Allies (thanks to decryption addition, the head of most schnorkels was fitted of high-level German message traffic, an with a detection device that gave warning ofthe intelligence source known as "Ultra") were approach of Allied radars. 10 Since the U-boat was acutely aware of the possibilities of the new U already submerged when using its schnorkel, an boat designs. 14 The Type XXI and Type XXIII alert crew could usually dive deep and escape boats were the first conventional submarines before an attack could be launched even if an capable of rapid underwater manoeuvring. 15 Allied radar operator could distinguish the small Although they could sustain high-speed echo of the tube from the random returns manoeuvres for perhaps only an hour or an hour provided by ocean swells or flotsam and jetsam. and a half, these submarine were the most menacing known at that time. 16 German Schnorkel-equipped U -boats were sent into authorities assigned the highest priority to their the English Channel during the summer of 1944 production in July 1943, but the first few only to attack the heavy flow of shipping that became operational as the war ended.17 The sustained the Normandy beachhead; their potential impact of these vessels on the trans commanders learned that they could operate in Atlantic logistics of the Allied campaign in the most heavily defended waters. 11 The Allies Europe remains one of the most interesting had anticipated an aggressive response to the subjects for speculation. Fortunately for the June 1944 invasion and had prepared a Allies, however, the war was fought with older, comprehensive defence in depth of the ChanneL Type VII and Type IX. U-boats re-equipped with Massed ASW forces devastated U-boats not yet schnorkels and radar detectors. equipped with schnorkels (at the time a majority) but found schnorkel-equipped submarines a 24 https://scholars.wlu.ca/cmh/vol7/iss3/3 2 McLean: Confronting Technological and Tactical Change: Allied Anti-Submar The only area where schnorkel-fitted boats of the bottom is another factor which can be could achieve any success was in the coastal largely ignored in deep water, but not along the areas near ports and focal points of shipping. 18 coast. Rocks and shoals, as well as shipwrecks Although both Allied and German naval officers and schools of fish, produce convincingly considered in late summer 1944 that a return submarine-like echoes. Finally, the effect of fresh to open-ocean wolfpack operations would be the water from rivers and streams is frequently only way in which Allied shipping could be pronounced, and, in combination with interdicted effectively, and though such tactics temperature variations, cause especially dense might arguably have been practical using the new layers to form in the water that so affect the submarines, 19 the Germans realized that such propagation of sound as to effectively "blind" the tactics were impossible with the older U-boats. sonar of a searching warship. The Germans were encouraged by the ability of schnorkel-equipped submarines to operate in Consequently warships acting as close escort such heavily defended waters as the English to convoys rarely detected aU-boat in shallow ChanneF0 but were acutely aware that simply water before the submarine attacked. During this , surviving was not enough. Shipping had to be stage of the war U-boats often rested on the destroyed if the apparently inexorable Allied bottom in the vicinity of shipping traffic, rising advance was to be slowed. and too few ships up to fire a torpedo only when alerted by the were being sunk. Still. the schnorkel-equipped sound of an approaching convoy. Waiting to boats had just garnered the greatest success that detect convoys passively by their noise did not German submarines had enjoyed since the fall prove adequate, however. and in mid-December of 1943. As the summer of 1944 waned, 1944 BdU ordered all U-boats to remain at Befehlshaber der U-boote (U-Boat periscope depth during daylight hours so as to Headquarters. or BdU) decided that until increase their chance of finding targets visually. 24 improved types ofU-boats became operational, This helped the U-boats somewhat. and the U an offensive in coastal areas offered the best boat's chance of being detected by the escort chance of inflicting losses on the Allies. 21 before it attacked remained slight. After firing. the submarines usually either made off at slow speed just above the bottom. sometimes simply Shallow Water Submarine Warfare drifting with the tide, or rested on the bottom until searching forces had moved on.2s Close W ith their decision to move into coastal escort vessels had little chance to destroy a waters using older schnorkel-equipped U submarine employing such snap attacks and, boats, the Germans created a difficult problem since they had to remain with their convoy. could for the Allies. Shallow water ASW had been rare rarely stay in the vicinity of an attack long enough since early in the war. The Germans had found to conduct the prolonged and methodical search operating in coastal waters without schnorkels necessary to find a bottomed or deep. slow prohibitively difficult because of constant Allied moving U-boat. air patrols.22 In the first half of the war U-boats endeavoured so consistently to escape to deep Aircraft patrolled coastal waters incessantly water that Allied doctrine prior to the Normandy but rarely spotted schnorkels, and had great Invasion presumed that after an attack or upon difficulty attacking even if an aircrew was being detected. U-boats operating in shallow fortunate enough actually to find one.2 New (i water would head for deep water. The possibility sensors such as sonobuoys were being that aU-boat might either settle on the bottom introduced, but these were in a primitive stage or move closer inshore was "considered of development. On occasion U -boats were unlikely. "2:l detected by sonobuoys and then attacked by air dropped homing torpedoes - a very modern As it became apparent that the U-boats had tactic indeed - but too rarely to have any begun to do exactly that, the Allies discovered significant impact on the campaignY The main that shallow water ASW was, for many reasons, effect of ASW aircraft was the caution that their a particularly demanding art. Sound conditions pervasive presence induced among most U-boat are extremely changeable in shallow water, a crews. Seldom daring to surface, U-boats function of tidal and current variations. The effect travelled slowly underwater at a fraction of their 25 Published by Scholars Commons @ Laurier, 1998 3 Canadian Military History, Vol. 7 [1998], Iss. 3, Art. 3 surfaced cruising speeds, groping for clues to The strategic bombing campaign, for its part, their actual position.28 Radio communication succeeded in stopping U-boat production as the with BdU, which required the submarines to war drew to a close, and mines laid in the Baltic surface and exposed them to the efficient Allied by these aircraft severely hindered the training radio-direction-finding network, became of new U -boat crews. These achievements gave :lO extremely intermittent and contributed to a promise of causing the entire German submarine growing inability at BdU to follow operations at campaign eventually to wither. but there was little sea.29 Overall, ASW aircraft substantially reduced that strategic bombers could do to counter the the effectiveness of U-boats at sea, but did not hundreds of U-boats that were already neutralize them. More direct measures were operational. needed. "' American hunter-killer groups had proved 0) 9 formidable U-boat killers during 1943 and early "!' 1944, but rarely encountered German Ol ~ submarines in the later part of the war. As a ::J result of rationalization of command structures [t and operating areas among the Allies in early 0 1943, the USN handled the central Atlantic and the eastern seaboard of the United States, while British and Canadian forces were primarily responsible for the north Atlantic. Since by mid- 1944 few U -boats remained in the central Atlantic, and not many submarines could reach the eastern seaboard when they travelled submerged, USN hunter-killer groups seldom had any opportunity to show their mettle after 1943. When U-boats began to penetrate into US waters in the last few months of the war, the USN demonstrated remarkable adaptability and success in countering them. 31 The growing strength of the USN as the European war closed did allow that navy to "maintain nearly as many Left: An unlikely place to find an air force photographer! However. a good shot of the dummy schnorkel mastfitted to the British training submarine HMS Unseen. based at Digby. NS in early 1945. Below: A hard targetfor radar or human eye. The dummy schnorkel and search periscope of HMS Unseen as they appear when the sub is submerged. https://scholars.wlu.ca/cmh/vol7/iss3/3 4 McLean: Confronting Technological and Tactical Change: Allied Anti-Submar ships and aircraft in the Canadian zone [the tactically sound was a lively one both at the time waters adjacent to Newfoundland and the and since. However, the argument was reduced Canadian coast] as the entire naval and air to irrelevancy in the face of the new German strength normally available to the commander tactics, which largely denied both Anglo in-chief Canadian Northwest Atlantic."32 Canadian and American forces the intelligence Nevertheless. it was at this late stage a minor they required to use these groups in their player, because the main battle against schnorkel preferred ways. :Js U -boats was now in the waters around the British Isles, the one area still within reach of most U The great strength of support and hunter boats in the beleaguered German fleet. Almost killer groups was that because they were not by default, therefore. the main burden of counter preoccupied with protecting convoys they had measures against the coastal campaign by great flexibility. This allowed them to adopt schnorkel-equipped U-boats fell toRN and RCN procedures which became the foundation of "support groups." eventual Allied success in the contest with inshore submarines. Prolonged searches for U boats became a staple in their tactical inventory, Support Groups as did extended operations in geographical areas where U-boat activity was high. The ships of these groups were theoretically well-prepared to deal with the new German During 1944 the number of support groups tactics. They were the best equipped for ASWin in the North Atlantic grew to 17 RN and 7 RCN.:Hi their respective navies. By this late stage of the The predominance of the Royal Navy in support war, the majority were either frigates or an groups was partly a result of its larger size, but equivalent class of vessels. fitted with the most it also reflected the greater role the Royal modern weapons and sensors. The role of Canadian Navy continued to play in the close support groups was to find and destroy U-boats escort of north Atlantic convoys. The reason for wherever they operated. this inequitable distribution is not clear in the records, but it is not unlikely that the RN The idea of a group of escorts whose primary considered close escort a less demanding task role was to counter U-boats was straightforward than operating as a support group, and therefore enough. Experiments as early as 1941 had more suited to the RCN's capabilities. indicated how effective such an organisation could be.:tl However, it was only when enough Most support groups were allocated to ships became available to provide close escorts United Kingdom waters, which senior Canadian for all convoys that support groups were finally and British officers appreciated was the critical established in significant numbers. As the battle area. This left the Canadian coast inadequately on the North Atlantic convoy routes approached protected, but despite the risk the Canadian its peak in the spring of 1943, the formation of Naval Staff recommended that the five RCN five such support groups was one of the major support groups under the operational control of initiatives taken that resulted in the crushing the RN remain in UK waters "unless there is a defeat ofwolfpack attacks.34 real need for them. "37 In other words, unless intelligence provided clear indication that a large The Royal Navy most commonly used number ofU-boats were en route to Canada or support groups as rapid reinforcements for shipping losses soared. convoys either under attack or expected to come under attack. This practise was extremely Despite the advantage of vastly superior effective as an antidote to wolfpacks, but lost its numbers, adequate time to search and good utility as the Germans changed their tactics. USN equipment, support groups found the task of Hunter-Killer Groups, the American equivalent locating schnorkel-equipped U-boats in coastal of support groups, emphasized the actual waters extremely challenging. The first hunting of U-boats using radio-intelligence. experience these ships had with the new German These USN groups were enormously successful tactics was in the difficult shallow waters of the in the summer and fall of 1943. The debate over English Channel in the wake of the Normandy which approach was more strategically and invasion. One particularly graphic account is 27 Published by Scholars Commons @ Laurier, 1998 5 Canadian Military History, Vol. 7 [1998], Iss. 3, Art. 3 provided by Allan Easton, who commanded the after "Scabbard" was first circulated before Allied destroyer HMCS Saskatchewan at the time. On anti-submarine ships began to demonstrate 7 June 1944, his ship was narrowly missed by notable proficiency in any of the tactical two German torpedoes, one of which apparently techniques and procedures required to defeat exploded prematurely, the other being detonated schnorkel-fitted U-boats. by the anti-acoustic-torpedo decoy deployed after the first explosion. While Saskatchewan and the A further reason for the somewhat measured three other destroyers in the group saw the U pace of the Allied response was that, initially, it boat's periscope several times - sometimes in seemed likely that U-boat operations inshore very close proximity-and conducted numerous were only a passing phase dictated by the attacks upon it. as well as a similar opponent Normandy Invasion. The limitations that U-boats the next day, the only result was, in Easton's laboured under in shallow water were well words, "dead or unconscious cod rising to the appreciated, and Allied intelligence considered surface. "~1H that a return to (potentially) more effective wolfpack tactics would ensue once the Germans Compounding the difficulties faced by these gave up their efforts (largely futile in terms of ships was the lack of a coherent tactical doctrine. real effect) to interdict shipping through the Some procedures had been prepared in English Channel.42 As August ended. however. anticipation of the Invasion, and the techniques and the U -boats fled from the Biscay ports. firmer developed to combat U-boats in deep water could evidence of German intentions came to light. It be applied to some extent in shallow water, but became clear then that U-boats would it soon became evident that the Germans had concentrate in the coastal waters around Britain brought new and mysterious elements to bear and not against mid-ocean convoysY and a good deal more was required in response. The first hints of new German tactics (such The Inshore Battle: as resting on the bottom to avoid detection) came Tactics and Technology from prisoners of war rescued from U-boats destroyed in the English Channel as the Invasion The opening operations of the U-boats in the began. The first Allied message discussing this British littoral were comparatively small in change appears to have been promulgated on scale, mostly because the evacuation of the 01 July 1944Y9 However, it was not until 25 Biscay bases had dislocated the German navy's August that the first new tactical search plan organisation. A handful ofU-boats were sent out (known as "Scabbard") that dealt with "static" to what were hoped, albeit more on the basis of tactics was adopted.40 In other words, it took estimate than solid intelligence, to be the most two to three months for the Royal Navy to react profitable hunting areas. The most successful as an organisation to the German change. U-boat ofthis period. the U-482, operated in the North Channel, the area just north of Ireland During this transition period, the ships made where shipping from North America had been do as best they could. Old tactics were adapted, routed since the fall of France. This boat's patrol or improvised plans were worked up within lasted from 16 August until the 26th of individual groups.41 Although this was far from September, and she claimed three merchantmen, sufficient, the novelty of the situation militated one corvette and one rescue ship, taking two of against more rapid development of new tactics. her victims only fifteen miles from the Irish coast. It was also evident that a number of new tactical The success of this bold submariner in these procedures would have to be developed: waters came as something of a shock to the "Scabbard" was but the first. It must also be Allies. despite the experiences off Normandy. Not emphasized that simply promulgating tactical only were all the merchantmen in convoy when procedures was only the first step in actually sunk,44 but the U-boat traversed waters where a employing new methods; plans must be special effort had been made to detect and absorbed and practised by all ships before they destroy U-boats on passage.45 Although U-482 could be effectively employed, and in the best of was the only submarine to achieve significant conditions this takes a good deal of time. In the success during this period. her accomplishments event, it would be almost another six months 28 https://scholars.wlu.ca/cmh/vol7/iss3/3 6 McLean: Confronting Technological and Tactical Change: Allied Anti-Submar made it apparent that the Allies had a long way reaction by the close escort to a torpedo attack. to go in countering "static" tactics. "Artichoke" called for the escorts in the van of the convoy to reverse course back through the convoy columns en route to the stricken ship. Command and Tactics Details of "Basin" have not been found, but presumably it called for the close escort to Yf"'he analysis of U-482's attacks led to a change congregate near the stricken vessel as well. .1 in the command arrangements between Particular emphasis was placed on the close escort groups and support groups.46 importance of quick action as soon as there was Support groups had always been put under the evidence of the presence of aU-boat. Once the control of the Senior Officer of the close escort initial actions were completed, "Scabbard" was group of whatever convoy they had been sent to to be conducted by either a part of the close support. During the period when convoys at sea escort or, if one were available. by a support were the focus of German attacks, this group.50 arrangement was entirely appropriate; support groups, which rarely stayed with any convoy for The Admiralty summarized the new methods more than a day or two. necessarily had a less in a message in October 1944. This complete tactical picture than the Senior Officer recommended stationing escorts astern of the of the close escort."~ With the switch to static convoy so that they could "pounce" upon aU tactics by U-boats. however. the situation was boat in the wake of a torpedo attack. The radically altered. Since convoys were no longer synopsis of U-boat intentions in the final the focus of a running battle, support groups paragraph accurately outlined the new German were now tasked to operate in specific tactics, and stressed the change from previous geographical areas. Convoys were still methods: "supported" as they passed through these areas, but now the support group's knowledge of the U-boats can now operate inshore and are likely to adopt static tactics in place of the mobile peculiarities of a locality were far more important tactics which we have been used to dealing with. than the close escort's familiarity with the Static tactics involve the use of curly and gnat idiosyncrasies of a convoy. In particular. the torpedoes fired from U-boats which endeavour support group's knowledge of bottom conditions to lie in wait on the course of convoys. When no and wreck locations in a local vicinity became targets are available U-boats are likely to move critical. As a result in mid-September 1944 the with great caution and charge by snort [i.e. schnorkel] mainly by night. On approach of a senior officers of support groups were made hunting force [the U-boat] will probably bottom independent of the close escort when operating or may drift with tide near bottom." in support of a convoy.'18 The tactical procedures developed in the late In September 1944 the RN officially summer and early fall of 1944 remained acknowledged that U-boats would probably essentially unchanged for the remainder of the employ static tactics. From doubting that U -boats inshore campaign.52 In practice it was not would ever choose to bottom, the Royal Navy uncommon for standardized tactical procedures had swung almost completely around. In a to be combined or slightly modified as escorts message to all forces under his command reacted to unique situations. The general engaged in the fight against U-boats, Admiral Sir principles in inshore ASW were, however, Max Horton, Commander-in-Chief Western constant: quick reaction and concentration of Approaches, put forth the view that, "When a forces in the vicinity of an attack to deter further ship in convoy is torpedoed in waters where a attacks and to destroy the enemy, followed by a U-boat can bottom it should be assumed that it prolonged hunt by support group ships if the will do so provided immediate scaring tactics enemy, as generally happened, eluded the initial [i.e. urgent ASW attacks] are adopted."49 Ships response. of the close escort were given detailed new tactics as well, which varied depending upon whether a Patrolling geographic areas near shipping support group was present or not. Previously routes where U -boats might be lurking entailed developed tactical procedures, "Artichoke" by day endless hours of repetitious effort, most of it to and "Basin'' by night were adopted for the initial classify the innumerable wrecks and other non- 29 Published by Scholars Commons @ Laurier, 1998 7 Canadian Military History, Vol. 7 [1998], Iss. 3, Art. 3 HMCS La Hulloise entering port at Liverpool, England, 7 April 1945. La Hulloise. a River-class ji·igat.e. worked wilh both Escort Group 16 out oJ Halifax and Escort Group 25 based in Londonderry and Rosyth. She was partially credited with the sinking oJ U- 1302 in March 1945. submarine contacts found in British waters. Detection, Classification, and Tactical procedures for these patrols evolved Prosecution with expeiience gained duiing the winter of 1944 I 45. Essentially there were two choices: either to J\ ctually locating a submarine was a serious proceed at slow speed so that anti-acoustic ~roblem throughout the campaign. The torpedo decoys were unnecessary and maximum relative number of U -boat detections by asdic in asdic [i.e. sonar] effectiveness was assured, or the last year of the war was not markedly less to proceed at moderately high speed, searching than it had been in earlier yearsY However, the with decoys deployed. The first approach gave a comparative ineffectiveness of other detection relatively high probability of submarine detection assets (such as high-frequency direction-finding in the swept water but covered little area, (HF I DF) of radio signals, radar or visual produced numerous false contacts, and gave U sight.ings) because of the almost constant boats some opportunity to evade because of the submergence ofU-boats meant that reliance on warships' slow speed of advance. The second asdic was far greater. With only one effective option was less likely to detect aU-boat, but was sensor, the total number of detections dropped more likely to disturb any submarine present in dramatically. Initially, this led to grave concern the search zone because of the greater area that in some quarters that asdic did not work in could be swept. If enough groups were available, shallow water. The truth was more complex. then a combination of these methods could be Asdic was somewhat less effective in shallow productive, because U-boats intent on avoiding water because of the number of non-submarine the noisy high-speed groups might be ambushed contacts that confused operations there, but by the slow, stealthy ones. 53 However, because there were also areas in both deep and shallow there were seldom sufficient numbers in one water where U-boats could operate with relative place for this ambitious scheme, most groups impunity due to hydrographic factors. The issue alternated between the two approaches in both deep and shallow water was initial depending upon weather and asdic conditions detection, and the Second World War asdic was and on the amount of time available to linger in a poor sensor for this role (now known as an area. surveillance) because of its extremely limited 30 https://scholars.wlu.ca/cmh/vol7/iss3/3 8 McLean: Confronting Technological and Tactical Change: Allied Anti-Submar range. The overall problem was not so much with Good navigation was essential to reduce the asdic itself as that there were so few other number of unnecessary attacks, and ensure that detection opportunities to complement asdic escorts remained in contact with targets that searches - between mid -1941 and mid -1944 proved to be a "live" submarine. Because of the most boats had first been detected when frequency of non-submarine contacts, it was not surfaced, either by radar or visually. "5 unknown for escorts to be seduced from a valid contact onto a nearby non-submarine contact. Once an asdic contact was gained, the A veteran of the inshore battle recalled an problem quickly became (as it is today) one of incident in which one "U-boat kept us chasing classification- that is, deciding whether or not all night, and I am not sure that we did not start the contact was a submarine. Contacts that after one U-boat and finish with another."58 The seemed convincingly like submarines were often value of an accurate and easy to use radio made.56 Escorts were advised early in the navigation system while searching in such campaign to "plaster" each one.57 This advice difficult waters can scarcely be overstated. In the was valid but obviously expensive. Not only did last part of the war such a system, known as it result in the expenditure of an enormous Gee, became available in the English Channel amount of ordnance, but the time required to and southern Irish Sea, and many, although not attack all contacts disrupted searches for real all, escorts in support groups were fitted with U -boats. The repeated detonation of large the necessary receivers. Gee allowed escorts to amounts of explosive in the vicinity of the escorts differentiate between contacts as close as one also caused wear and strain on the ship's hulls. thousand yards apart, and therefore enabled Expeditious classification of bottomed asdic warships to plot wrecks quickly and accurately. contacts became something of a "holy grail," and Groups fitted with this equipment became very escorts assiduously pursued it. Despite their best familiar with the wrecks in their assigned patrol efforts. all methods remained less than areas after an initial period of endless contacts. satisfactory. Gee was so valuable that support groups that were only partially fitted complained in no The size of the target as determined by asdic uncertain terms that more sets were essentiaJ.5n proved to be a rough guide at best. The sound quality of the echo returned by a contact was Ships also used buoys to assist in their similarly equivocal, with many non-submarine prosecution of bottomed contacts. The "dan" contacts providing far sharper and clearer echoes buoy, a small buoy that could be anchored in a than the real item. A bottomed contact could be specific spot, was the recommended aid. Its identified if the vessel was equipped with an employment prevented escorts from drifting appropriate echo sounder, but this technique inadvertently away from a contact through being required a highly skilled crew. The Type 761 echo either set by tide or blown by wind while the sounder provided the best results, especially if contact sat immobile on the bottom. The value the vessel was adept enough to pass directly over of such an aid to location in the featureless sea aU-boat in the same direction that the U-boat was demonstrated on a number of occasions, was lying. This produced a trace that showed and its use was continually advocated by training the length, breadth and height of the U establishments.60 boat,including the distinctive outline of its conning tower. Even this result was not definitive, for the waters around the British Isles had Operational Results become the resting place of many wrecked submarines. A comparison of the position of the The lowest point in the campaign occurred in contact with a chart of all known wrecks would, December 1944. During that month, U-boats given precise enough navigation, provide a final torpedoed 11 ships in British waters.rit No U determination of whether the contact was real boats were sunk in the wake of these attacks, or not. Nevertheless, even if the wreck chart and only three U-boats were destroyed by anti indicated that the boat in question was long dead, submarine forces in U.K. coastal waters: two by a good echo sounder trace would warrant a ships and one by aircraft. 52 The total number of cautionary attack. U-boats lost during the month was 14, but three were the result of accidents, three were bombed 31 Published by Scholars Commons @ Laurier, 1998 9