Hitler’s U-Boat War- The Hunted 1942-45

by Clay Blair

  Throughout the Atlantic Convoy Conference, those in attendance labored under two grim intelligence assumptions that, however, proved to be utterly wrong: that the U-boat force was to increase in size dramatically in 1943, and that Allied code-breakers would again lose four-rotor Enigma for at least several months.

  As to the first assumption, on March 1, 1943, senior Allied intelligence officers projected that by the end of the year, December 31, 1943, the Germans would have in commission a force of 613 U-boats. This figure was arrived at by assuming that the Germans would commission 320 new U-boats in 1943 (26.6 per month), and that the Allies would sink 124 U-boats during the year (10.3 per month). When the projected net gain of 196 U-boats (320 new, less 124 sunk) was added to the 417 U-boats assumed to be in commission on January 1, 1943, the result was 613 U-boats.

  Owing to an unanticipated great increase in Allied U-boat kills in 1943, these figures were to be well off the mark. According to records at U-boat Control, on December 31, 1943, the U-boat force had not 613 but only 436 boats in commission, a gain of but nineteen boats in 1943. These included eighty-seven school boats, 181 boats in Baltic workup and R&D (“on trials, training and experiments”), but only 168 boats “on active service” at all battlefronts. The latter figure included thirty-two VIIs in the Mediterranean and Arctic, 130 VIIs and DCs in the Atlantic force, and six ducks in the Black Sea.

  The Atlantic U-boat force did not grow in the summer of 1943; rather, it shrank. The proximate force levels :

  As to the second grim assumption, the loss of four-rotor naval Enigma, it was British codebreakers who made this forecast. They had learned from Enigma decrypts that on March 10 the Germans were to introduce a new short-signal code-book for weather reports, superseding that recovered from U-559 the previous October. Since the weather codebook was an indispensable part of the crib-finding process for the British bombe programmers, Bletchley Park “feared that the consequences would be fatal,” as the official British intelligence historian put it.

  During the convoy conference, on March 9, the Admiralty’s Assistant Chief of Staff for Trade, John H. Edelsten, memoed First Sea Lord Pound: “The foreseen has come to pass. DNI [Director of Naval Intelligence] reported on March 8 that the Tracking Room will be ‘blinded’ in regard to U-boat movements, for some considerable period, perhaps extending to months.” Pound relayed this bad news to the Vice Chief of Naval Staff, Henry R. Moore, who was in Washington for the Atlantic Convoy Conference, in these words: “U-boat Special Intelligence has received a severe setback. After 10th March it is unlikely that we shall obtain [break] more than 2 to 3 pairs of days per month and these will not be current.” Pound added a hopeful postscript: “After 2 to 3 months the situation should improve considerably.”

  However, the Allies lost four-rotor Enigma for only about ten days. In one of the great intelligence feats of the war, British codebreakers at Bletchley Park, who had sixty three-rotor bombes on line, broke back into four-rotor Enigma on March 19. The official intelligence historian wrote that in the 112 days from March 10 to June 30, the British read four-rotor Enigma for 90 days, or 80 percent of the time.

  The senior conferees of the Atlantic Convoy Conference included Admiral King (Chair); his chief of Staff, Richard S. Edwards; British Admiral Percy Noble, fresh from command of Western Approaches, then serving as senior British naval officer in Washington; the aforementioned Vice Chief of the British Naval Staff, Henry R. Moore; and the senior Canadian officer in Washington, Rear Admiral V G. Brodeur.

  King opened the conference with brief remarks, then turned the chair over to Edwards. In his remarks, King said that he still believed that convoying was not only the best way to protect Allied shipping but the only way. “A ship saved,” he emphasized, “is worth two built.” The “safe and timely arrival” of convoys should continue to be the guiding strategic principle; hunter-killer operations, secondary.

  King also expressed grave concern over the dangerously increasing congestion in New York harbor. From September 1942, when the North Atlantic convoys shifted to New York for departures and arrivals, to February 1, 1943, there had been 123 collisions of oceangoing vessels (involving 246 ships) in the harbor. Of greatest importance, King stressed, the old battleship Arkansas had nearly been rammed twice while at anchor.*

  The conferees reached a number of important decisions that were promptly ratified by the three governments. Among the most important:

  The North Atlantic Run

  The British and Canadians were to assume full—and sole—responsibility for the escort of cargo convoys on the North Atlantic run. The American command, Task Force 24 in Argentia, would withdraw as would the last American escort group, A-3, and the American “shuttle” based in Iceland.* Ships bound to and from Iceland were to sail between the Americas and British Isles in North Atlantic convoys, thence to and from Iceland in the existing convoys, UR-RU (United Kingdom to Reykjavik and reverse), escorted by British-controlled warships.

  The Halifax and Slow and Outbound North convoys on the North Atlantic run would continue generally as before but with several modifications. As Admiral King had suggested, to relieve the congestion in New York, Slow Convoys (SC) and Outbound North (Slow) convoys (ONS) would originate and terminate in Halifax, Nova Scotia, commencing on March 31.† As earlier, ships for Halifax would travel to and from that port in the existing convoys HB-BX (Halifax-Boston and reverse) escorted by Canadian warships and by U.S. and Canadian aircraft. Ships would travel to and from Boston in the U.S. interlocking convoy system.

  The Mid-Ocean Escort Force (MOEF), to be controlled by the Admiralty, was to consist of fourteen escort groups of six ships each (eighty-four warships), seven groups to be provided by the Canadians and seven groups to be provided by the British. To accommodate Canadian needs, the three Canadian MOEF escort groups that had been withdrawn for training in the British Isles and the fourteen surviving Canadian corvettes assigned to three Torch escort groups were to be returned to Canada.

  Upon the withdrawal of the American Task Force 24, the Canadians would assume operational control of the western portion of the North Atlantic run and XB-BX convoys. Designated Canadian Northwest Atlantic Command, the area comprised all waters west of a line at 47 degrees west longitude and south to 42 degrees north latitude (Boston). A Canadian Western Escort Force comprised of eleven groups (increased from the existing eight) would guard the convoys in this area. To man these groups, in addition to the return of Torch and other corvettes, the Canadians would retain the eleven British destroyers on loan in Canadian waters.‡

  The Slow Convoys were to sail from Halifax every eight days, commencing with convoy SC 125 on March 31. The HB-BX convoys were to sail from Halifax to Boston every four days, commencing with XB 38 on or about March 23, after Outbound North (Slow) 171 arrived in Halifax. Thereafter, Outbound North (Slow) convoys to Halifax were to be renumbered from 1, to distinguish them from the (fast) Outbound North (ON) convoys to and from New York.

  To meet the urgent British demands for an increase in imports, which President Roosevelt had promised, the sailings of the fast HX convoys from New York and the reverse, ON, from the British Isles were stepped up and the size of the convoys was increased in most instances to about sixty merchant ships plus eastbound Landing Ships, Tank (LSTs). Admiral King stoutly resisted a British proposal to increase the size of convoys on that route to eighty ships. That was too many merchant ships for one escort group (of six ships) to properly guard, he asserted. He warned that the external and internal repercussions over “heavy American ship losses in excessively large and inadequately protected convoys” would be strident and difficult.

  The stepped-up pace of convoy sailings on the fast HX-ON route was to take place as follows. Commencing with HX 230 on March 18, the next two convoys were to sail every seven days. Convoy HX 233 was to sail five days after HX 232. Convoys HX 234 to HX 236 were to sail every six days. Convoy HX 237, sailing on April 30, and all succeeding HX convoys were to sail ever
y five days. In addition, in March a “special” (or extra) convoy, HX 229A, was to sail. Commencing with ON 173, fast westbound convoys were to sail on a similar schedule, until reaching a five-day interval after ON 178, which was to sail on April 12.

  The British were to continue sole responsibility for the convoy routes between the British Isles and the Mediterranean (KM-MK), Sierra Leone and other West African ports (Outbound South or OS and the reverse, SL), and for the Winston Special (WS) military convoys. To maximize the use of British escorts on these routes, the Admiralty was to combine KMS and OS convoys on a twenty-day cycle, and KMF and WS on a thirty-day cycle. To further economize on local escort deployment at Gibraltar, every effort was to be made to synchronize the sailings of UGF and KMF convoys as well as UGS and KMS convoys. When sufficient escorts became available, the British were to resume the sailing of medium and small shallow-draft vessels in Outbound Gibraltar (OG) and Home-bound Gibraltar (HG) convoys.

  The British were also to continue sole responsibility for the JW-RA convoy routes to and from northern Russia (Murmansk, Archangel). These were to be comprised mostly of American cargo ships, such as the Liberty ships, but there were to be no American warships in the escort. Consisting of a maximum of thirty cargo ships, these convoys were to sail on a forty-two-day cycle.

  The British and Canadians were to provide five hunter-killer groups (support groups) to reinforce threatened convoys on the North Atlantic run. These were to consist of three to five destroyers, sloops, or frigates, and, as they became available, the British “jeep” carriers Archer, Avenger, Biter, and Tracker, one carrier per group. The first of the American hunter-killer groups scheduled to become combat ready, consisting of the “jeep” carrier Bogue and five destroyers, was to be loaned to the British-Canadian North Atlantic run. British merchant aircraft carriers (MAC ships with three or four Swordfish airplanes but no catapult) were to sail in each of the slower convoys (SC, ONS), commencing in May, when the weather was more favorable for aircraft operations.

  The Middle Atlantic Runs

  The Americans were to assume full—and sole—responsibility for the escort of convoys on the three routes in the Middle Atlantic: UG-GU, OT-TO, and CU-UC. Since these convoys sailed at much greater intervals than those on the North Atlantic run, fewer escort groups were required to guard them. These groups were made up of the five Atlantic-based Treasury-class Coast Guard cutters, new and old destroyers, and when they were to be available, destroyer escorts.

  The UG-GU convoys between New York and Gibraltar sailed on fast (fifteen-knot) and slow schedules, like the convoys on the North Atlantic run. Fast convoys (UGF, GUF), which were comprised of troopships as well as cargo ships, sailed every twenty-five days. The slow convoys (UGS, GUS) then sailing every twenty-five days, were to sail every fifteen days commencing in May.

  The fast (14.5 knots) OT-TO tanker convoys sailed between Aruba in the Caribbean and Gibraltar every twenty-eight days. Upon returning in ballast to the Caribbean, the tankers were to reload with oil and sail without escort to New York, deposit that load of oil in the “New York Oil Pool,” then return to the Caribbean to reload for Gibraltar. Slower tankers on the North Atlantic run were to transship the oil in the New York pool to the British Isles. Meanwhile, the transatlantic escort groups (six destroyers per group) were to put into the U.S. Navy base at Guantánamo, Cuba, for refits, upgrades, and crew training.

  The fast (14.5 knots) CU-UC convoys, delivering oil directly from the Caribbean to the British Isles, sailed from the Caribbean every fifty-four days. The round-trip cycle consisted of a fifteen-day voyage to the British Isles, a six-day layover there, a fifteen-day return voyage to the Caribbean, and an eighteen-day layover. During the layover in the Americas, the tankers also were to make an unescorted round-trip to New York to deliver a shipload to the New York pool while the transatlantic escort groups refitted at Guantánamo.

  The Middle Atlantic convoy routes were to be reinforced by five hunter-killer groups (support groups). Each of these was to consist of four or five destroyers and American “jeep” carriers as they became combat ready. These were the Block Island, Card, Core, Croatan, and Santee. As more British “jeep” carriers became available, the Bogue support group on loan to the British-Canadian North Atlantic run was to be shifted to the American Middle Atlantic runs.

  The Atlantic Convoy Conference reached these decisions during early March when ship losses in the North Atlantic convoys were much heavier than usual. Appropriate concern was expressed over these heavy losses, but it is noteworthy that nothing was said remotely comparable to the fear expressed at the Admiralty about how the Allies faced the “crisis of crises” or that, owing to U-boat attacks, convoys might no longer be a viable means of protecting merchant shipping.

  Long- and Very-Long-Range ASW Aircraft

  By March 1, 1943, when the Atlantic Convoy Conference convened, the Allies had in place a powerful and growing force of long- and very-long-range ASW aircraft in the North Atlantic. It was far more impressive than is depicted in most accounts of the Battle of the Atlantic*

  In the first half of 1943, there were no U-boats operating in waters of the Eastern Sea Frontier,† Ably commanded by Admiral Adolphus Andrews, that battle-front encompassed the entire United States East Coast from Maine to Florida. All merchant shipping in that area sailed in convoys guarded by escort groups drawn from a fleet of about two hundred warships.

  Since there were no U-boats along the East Coast and the convoys sailed close to shore, there was very little need for long-range ASW aircraft. However, Andrews maintained continuous air patrols to protect these unthreatened convoys. On February 25, 1943, he reported, he exercised operational control over 328 aircraft of which 192 were Navy and Coast Guard and 136 were Army Air Forces. The Navy and Coast Guard aircraft included ten Catalinas of Patrol Squadron VP 31 (deployed at Rhode Island, North Carolina, and Florida), six PBM-3C Mariners (at Norfolk), and eighteen blimps. The rest were short-range single-engine floatplanes, such as the Navy’s OS2U Kingfisher. The Army Air Forces planes included twenty-five B-18s (of Squadrons 4, 7, 12), twelve B-17 Flying Fortresses (of Squadron 20), thirty-eight B-25 long-range Mitchells (of Squadrons 3, 5, 6, 13, 14), and forty-four B-34 Lexingtons, the Army’s version of the Navy’s Ventura (of Squadrons 7, 11, 15, 16).

  In Canadian waters, north of the Eastern Sea Frontier where U-boats still operated, the Royal Canadian Air Force (RCAF), like the Royal Canadian Navy (RCN), was growing slowly and steadily gaining in effectiveness.

  The RCAF deployed nine ASW squadrons at the battlefront. Four (5, 116, 117, 162) were equipped with Catalinas/Cansos, one (10) with Digbys (USAAF B-18s), and four with Hudsons (11, 113, 119, 145). In addition, scores of Ansons in the Training Command flew practice missions over the Gulf of St. Lawrence, adding to the air coverage.

  The United States contribution of ASW aircraft in the Maritime Provinces remained substantial. One reason was that duty there was like a postgraduate course in ASW. U.S. Army and Navy aircraft crews could gain actual battle experience without fear of reprisal from Axis aircraft.

  The American units continued to rotate. As related, U.S. Navy Catalina Patrol Squadron VP 84 moved east to Iceland in the fall of 1942. Catalina Patrol Squadrons VP 82 and VP 93 returned to the United States to be reequipped with a different aircraft, the Lockheed Ventura, of which more later. These departing squadrons were in part temporarily replaced by six Catalinas of Squadrons VP 31 and VP 52 from the States. As will be described, the Army Air Forces B-17 ASW Squadron 20 at Gander, Newfoundland, returned to the States, replaced by other Army and Navy aviation units.

  Clockwise around the North Atlantic, next came the vital Allied ASW aircraft bases in Iceland. By March 1943, the whole of Terence Bulloch’s pioneering RAF Squadron 120, comprised of a dozen to fifteen B-24 Liberators, had deployed there. These stripped-down, very-long-range aircraft reinforced threatened convoys in the Greenland “Air Gap.” The dozen Catalinas of U.S. Navy Patrol Squadron VP 84
provided escort for threatened convoys east of the “Air Gap,” as did the Catalinas of RAF Squadron 330, manned by Norwegian crews.

  Continuing farther east across the North Atlantic, RAF Coastal Command deployed ninety-six long- and very-long-range aircraft at bases in Scotland and Northern Ireland. These were all four-engine planes: a dozen very-long-range B-24 Liberators (Squadron 86), two dozen B-17 Flying Fortresses (Squadrons 206 and 220), and sixty Sunderlands (British Squadrons 201, 228, and 246, and Canadian Squadrons 422 and 423). These planes provided escort for convoys to the northwest, west, and southwest of the British Isles.

  In southern England, RAF Coastal Command deployed about seventy-two other four-engine aircraft, most of which conducted patrols in the Bay of Biscay or southward toward Portugal. These were a dozen B-24 Liberators (Squadron 224), two dozen Halifaxes (Squadrons 58 and 502), and three dozen Sunderlands (British Squadron 119, Australian Air Force Squadrons 10 and 461), As related, the twenty-four B-24 Liberators of U.S. Army Air Forces ASW Squadrons 1 and 2 redeployed from southwest England to Morocco in March 1943. (Otherwise the total in southern England would have been ninety-six four-engine aircraft.)

  Also in southern England were three squadrons of the twin-engine workhorse Wellingtons, comprising thirty-six aircraft. Many of these planes had been fitted with Leigh Lights, the powerful searchlight that was utilized in the final mile of a low-level night attack on a U-boat. One of the squadrons (RAF 304) was manned by Poles, another (RAF 311) by Czechs, the third (RAF 172) by British crews.

  Finally, at Gibraltar and Port Lyautey, Morocco, there were seventy-two long-range aircraft. These were the twenty-four B-24s of the U.S. Army Air Forces’s 480th Group (ASW Squadrons 1 and 2), thirty-six Catalinas (British Squadron 202 at Gibraltar, USN Squadrons VP 73 and YP 92 at Port Lyautey), and twelve Wellingtons (British Squadron 179 at Gibraltar). These aircraft provided protection for the UG-GU convoys to the westward as well as convoys going to and from West African ports.