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

by Clay Blair

  4. Rather than extending a friendly welcome, as hoped, French military forces in Morocco and Algeria might oppose the Allied landings vigorously, as they had opposed the recent British landing in Madagascar.

  5. The notoriously rough seas on the open Atlantic coast of Morocco might well foil the attempts to mount an amphibious assault and occupy that country.

  Influenced in part by the shortage of merchant shipping and warships for escort, the Torch D day fluctuated. It was first set for October 7, then postponed to November 8. In a message on September 4, Roosevelt informed Churchill that the U.S. Navy would provide Torch the bulk of the fighting power of the Atlantic Fleet. Viz.

  3 battleships (1 modern)

  1 fleet carrier (Ranger)

  2 “jeep” carriers (later, increased to 4)

  5 cruisers (2 heavy)

  40 destroyers

  6 minesweepers

  The American forces landing in Morocco were to be supported by six new, pre-positioned fleet submarines. They were to provide weather reports and homing beacons and later to blockade the unfinished but armed French battleship Richelieu at Dakar, Senegal. These six fleet boats were the first American-manned submarines assigned to combat in European waters.*

  • GUADALCANAL. The efforts by the Japanese to drive American forces from Guadalcanal intensified in the fall of 1942. In addition to the devastating losses the American Navy incurred in August and September, as related in Volume I, the Americans suffered further heavy warship losses during several naval battles in the Solomon Islands chain in October and November. These included the carrier Hornet and three more modern destroyers, Duncan, Meredith, and Porter sunk, the carrier Enterprise, the new battleship South Dakota, the light cruiser Boise, the modern destroyers Farenholt and Smith severely damaged. The battleship South Dakota and the modern destroyer Mahan collided, resulting in heavy damage to Mohan.

  • ATLANTIC CONVOYS. Owing to several factors, including the commitment of warships for Murmansk convoy PQ 18 and for Torch, the Allies made major changes in the North Atlantic convoy networks. The most important was to designate New York rather than Canadian seaports as the primary assembly and sailing point for Halifax and Sydney (or Slow) convoys. This change, which took effect on September 17, enabled the Allies to eliminate most of the Boston-Halifax (BX) and Halifax-Boston (XB) convoys, to shrink the Canadian local escort force, and to reduce drastically the heavy ship traffic in the Cape Cod Canal, where the possibility of another lengthy shutdown due to an accident was still a matter of serious concern.

  At this same time, the Allies approved final plans for a second major transatlantic convoy route. Designed initially to directly support Torch and other Mediterranean operations, this route was located in the more southerly latitudes of the Middle Atlantic. Fast and slow convoys outbound from America to support Torch were designated United States-Gibraltar (UGF and UGS). The reverse fast and slow convoys for returning ships were designated Gibraltar-United States (GUF and GUS). In addition to surface-ship escorts, these convoys were to be provided with long-range air escort from bases on the East Coast of the United States, Bermuda, Morocco, and Gibraltar.

  In very short order, this all-American Middle Atlantic convoy route would become a major line of communications from the Arsenal of Democracy to the Mediterranean theater of war. Scarcely mentioned in accounts of the U-boat war, from its inception in the late fall of 1942 to the surrender of Germany in May 1945, about 12,300 Allied ships in about three hundred different convoys crossed the Atlantic east or west by that route.

  These convoys were at first escorted by American destroyers, later by American destroyers and destroyer escorts, supported by American “jeep” carrier hunter-killer forces. The close escorts—usually about eight per convoy—refueled from tankers at sea. Because of the great distances entailed, the shortage of Type VII attack U-boats and U-tankers, and the decision to concentrate maximum force on the North Atlantic run, the Germans could not simultaneously wage a U-boat war against the Middle Atlantic route. The best they could do was to mount glancing attacks on the eastern end of the route between the Azores and Gibraltar, but that area was soon saturated with radar-equipped Allied air and surface escorts based at Gibraltar and Morocco (and later, the Azores), making U-boat operations no less perilous than operations in the Iceland-British Isles area. As a result, in twenty-eight months of combat operations, the Middle Atlantic convoys lost only about twenty-five merchant ships (.002 percent), another remarkable and unheralded victory by the U.S. Navy.*

  The final and absolute cancellation of Sledgehammer for 1942 and the decreasing likelihood of Roundup, the next planned invasion of France, in 1943, because of the demands of Torch, led Washington to make major changes in shipbuilding programs. Chief among these was the lowering of priorities for landing craft and the raising of priorities for the much-delayed destroyer escort and “jeep” carrier programs. On October 24, President Roosevelt notified Churchill that these and other adjustments would enable American shipyards to produce in 1943 seventy more destroyer escorts than planned (to a total of 336) and an additional two million deadweight tons of merchant ships (from about eighteen million deadweight tons to about twenty million).

  This message was crossed in passing by a letter from Churchill to Roosevelt, which was hand-delivered on November 4 by the British war production czar, Oliver Lyttelton. Among other “major points,” Churchill stressed the British requirement for additional merchant shipping from American production in 1943 (one million deadweight tons of tankers and 2.5 million deadweight tons of cargo ships) to provide a rock-bottom twenty-seven million tons of imports.

  No less important, Churchill implored Roosevelt to provide long-range convoy escorts on the North Atlantic run. “It is escorts that we need,” Churchill emphasized in italics, “even more than merchant ships. We want both, but I am all with those who say ‘A ship not sunk in 1943 is worth two built for 1944.’” He urged the “maximum construction of escort vessels which engine [manufacturing] capacity will allow” and a distribution of 1 escort to the British for every 1.37 escorts to the Americans.

  In pressing his case, Churchill continued to greatly inflate the “U-boat menace.” It was, he was sure, “our worst danger.” He went on in the bleakest possible language:

  It is horrible to me that we should be budgeting jointly for a balance of shipping on the basis of 700,000 tons a month loss. True, it is not yet as bad as that. But the spectacle of all these splendid ships being built, sent to sea crammed with priceless food and munitions, and being sunk—three or four every day—torments me day and night. Not only does this attack cripple our war energies and threaten our life, but it arbitrarily limits the might of the United States coming into the struggle. The Oceans, which were your shields, threaten to become your cage.

  Next year there will be many more U-boats and they will range far more widely. No ocean passage will be safe. All focal points will be beset and will require long range air protection.

  THE VIEWS FROM BERLIN

  Coinciding with the beginning of the fourth year of the war, the commander in chief of the Kriegsmarine, Grand Admiral Erich Raeder, met with Hitler on August 26 and September 28, 1942, to review the German naval picture. The U-boat commander in chief, Admiral Karl Dönitz, attended the second meeting to give Hitler a special presentation on the U-boat war.

  Hitler opened the second meeting by heaping praise on the U-boat arm for its great achievements. A stenographer noted that Hitler dismissed the recently released American shipbuilding figures* as propaganda, adding:

  He is convinced that the monthly rate of sinkings will continue to be so high that the enemy will not be able to replace his losses by new construction. He considers it impossible that the increase in production of the enemy shipyards comes anywhere near what propaganda would have us believe. Even if the enemy should succeed in launching ships relatively fast, he would still not have the necessary engines, auxiliary engines, other equipment and, most of all,
crews for the ships.

  Dönitz began his presentation to Hitler by explaining that U-boats “fighting off the American coast [were] no longer sufficiently profitable.” American ASW measures—air patrols in particular—and the extension of the convoy network were the main reasons. Except for a couple of “hot spots” (e.g., the Gulf of St. Lawrence, the Atlantic Ocean east and southeast of Trinidad), henceforth the U-boats were to move back to the North Atlantic and to the west coast of Africa near Freetown and south to Cape Town.

  Dönitz stressed the extreme difficulties his boats faced attacking convoys on the North Atlantic run. Growing numbers of radar-equipped, long- and very-long-range Allied aircraft (B-24 Liberators, B-17 Flying Fortresses, PBY Catalinas, Sunderlands) based in the British Isles, Iceland, and Newfoundland were able to provide convoys with air cover nearly all the way across the North Atlantic.† The presence of these aircraft made it very difficult for the U-boats to stay on the surface and shadow a convoy so that other boats could gather, or to haul around to a better or second shooting position ahead of the convoy. Distant and close radar-equipped surface escorts made it difficult for the U-boats to get close enough to the convoy formation to shoot.*

  As a result of intensified and improved Allied ASW measures, the inexperience of the U-boat crews, foul weather, and other factors, the tonnage sunk per boat in North Atlantic convoy battles was certain to decline. In order to reverse the decline—indeed, to return to the previous high levels of sinkings per U-boat—Dönitz said the U-boat arm urgently required:

  • A very-long-range, high-performance bomber, such as the prototype Heinkel 177 (HE-177), to scout out convoys and to warn of an approaching Allied air threat and to deal with that threat when it arrived.

  • An entirely new attack submarine with very high submerged speed to enable it to catch up to a convoy submerged, outmaneuver and outrun escorts during the attack and withdrawal phases, and shadow a convoy submerged long enough to bring up other members of the pack.

  In response to these sweeping proposals, Hitler had two very different reactions. On the one hand, he ducked any “definite promises” for a new aircraft, such as the HE-177, to support the submarines. To be sure, he recognized the need for the “best possible aircraft” for that purpose, but the German aircraft industry was already swamped by demands and could not take on mass production of a large bomber. On the other hand, Hitler strongly endorsed the construction of new U-boats with high underwater sprint speed. Such a submarine, Hitler enthused, “would have a revolutionary effect. It would immediately render ineffective the whole apparatus of enemy escort vessels and the construction programs of the relatively slow corvettes.”

  The idea for a German submarine with high submerged sprint speed was not new. In the early 1930s, a brilliant German engineer, Helmuth Walter, had proposed to the Berlin naval command a small, experimental design that in theory could run submerged at thirty knots for brief periods. It was to have diesel engines for surface cruising and a turbine propelled by decomposed hydrogen peroxide (H2O2) and water for submerged cruising. To reduce underwater drag, the hull was to be smooth, streamlined, and fish-shaped.

  Although the Germans had settled on conventional diesel-electric propulsion plants for the new generation of VIIs and IXs, the OKM† did not slam the door on Walter. In 1939 Berlin awarded him a contract for an eighty-ton, seventy-two-foot test vehicle, designated V-80. Built in the greatest secrecy in a screened-off area of the Krupp Germania-Werft yards in Kiel, the boat very much resembled a huge fish. Viewed bow on in cross section, she formed a figure eight. The living, working, and fighting areas were in the upper half of the eight; the lower half was used to store volatile hydrogen-peroxide fuel. In trials at Hela in 1940, the sleek V-80 achieved a sensational submerged sprint speed of 28.1 knots.

  Owing to the great success of the Types VII and IX in 1940 and 1941, and to lingering technical doubts about “Walter boats,” the OKM was not keen to increase support for the program. However, in January 1942, when Walter presented improved designs for large and small hydrogen-peroxide-powered submarines, Dönitz endorsed them enthusiastically and urged the OKM to back Walter to the fullest. In the wake of the intensified RAF Coastal Command ASW operations in the Bay of Biscay, Dönitz repeated that request on June 24, 1942. In lukewarm response, the OKM awarded Walter contracts for five experimental hydrogen-peroxide prototypes: one 170-foot, 600-ton “Atlantic” boat (U-791) and four small coastal boats (U-792 to U-795). On paper, all were capable of bursts of speed to twenty-five knots or slightly more while submerged.

  Although Walter had been designing hydrogen-peroxide submarines for ten years and one test bed (V-80) had been built and tried out with considerable success, by September 1942 none of the five boats under contract had progressed much beyond the design stage. Formidable technical problems remained to be solved, not the least of which was the construction of several plants capable of producing vast quantities of the hydrogen-peroxide fuel. Nonetheless, with Hitler’s enthusiastic approval, Raeder and Dönitz decided in the September 28 meeting to place orders for twenty-four of the small boats (U-1405 to U-1416 and U-1081 to U-1092) and “hoped to be able to make a decision within two months regarding mass production of the larger type.” In any case, Raeder stated, “mass production of these submarines is to be started as soon as possible, with corresponding adjustment of the present submarine construction program.”

  These little-noted decisions in the early fall of 1942 were among the most important of the U-boat war. They contain the profound implication that Raeder and Dönitz had concluded that Allied detection technology and air and sea supremacy had rendered the Type VIIs and IXs inadequate and obsolescent weapon systems. To successfully prosecute the U-boat war, an entirely new generation of U-boats, embodying quantum leaps in technology, was required. The most promising possibility was the Walter boat. Hence the huge gamble on the professor’s visionary ideas at this time.

  Obviously the fleets of Walter boats could not be produced overnight. It would take at least a year to complete, test, and debug the four small prototypes. The knowledge and experience gained from these four boats, as well as the twenty-four additional small boats on order were to be applied promptly to two big Walter “Atlantic” prototypes (U-796 and U-797), which were to be built in parallel with the smaller boats. That way, it was believed, many of the expected R&B delays could be avoided and the big “Atlantic” boats could be rushed into mass production.

  Pending the completion of large and small Walter boats in meaningful numbers, German yards were to continue production of Type VIIs and IXs. With patched-on improvements, these boats were to carry on the U-boat war to the best of their ability until Allied ASW measures completely checked or defeated them. Although it was expected that the sinkings by these boats would gradually diminish and that losses would climb, the continuing presence of Type VIIs and IXs in many separate areas of the world was to serve several important war aims apart from sinkings: to insure a continuation of wasteful Allied convoying, to tie down substantial numbers of Allied military assets in an ASW role, and to train and battle-harden a new generation of German submariners who were to man the Walter boats.

  THE CODEBREAKERS

  In September 1942, the Germans still enjoyed the advantage in the seesaw battle of naval codebreaking. In February 1942, they had introduced a fourth rotor to the naval Enigma machine in use on the Atlantic U-boat radio networks, again blinding Allied codebreakers. The Germans called this new cipher Triton; the British called it Shark. Absent “four-rotor bombes”* and “physical captures” (of short-signal weather and battle codebooks or Enigma key settings), the codebreakers at Bletchley Park in England had made little or no progress in breaking into four-rotor Enigma. On the other side of the hill, since February 1942 the swelling staff of the German codebreaking organization, B-dienst, was reading the Allied Cypher Number 3, employed jointly by the Americans, the Canadians, and the British for North Atlantic convoy operations. By Septemb
er 1942, B-dienst daily produced an unprecedented picture of Allied convoy sailings and the routes they followed sufficiently current for Dönitz to use the information tactically.

  The U.S. Navy was by this time thoroughly fed up with those Britons who still held tightly to the secrets of the bombe technology and had not yet provided the Americans with a long-promised bombe to copy for purposes of breaking Kriegsmarine (or naval) Enigma. The reasons for the delay were usually attributed to genuine British fears that the Americans would not keep secret the breaking of Enigma, as a consequence of which the Germans would turn to an entirely new and more difficult to break encoding system, blinding the British to the Luftwaffe Red and other Enigma ciphers they were reading. Doubtless the time-honored British custom of total secrecy regarding dissemination of codebreaking technology also played a role in the delay.

  British fears of losing all Enigma product were perfectly understandable and, furthermore, they were fueled by a startling new challenge in the ether. British radio-interception stations picked up increasingly heavy German traffic on a new, sophisticated non-Morse (Baudot) encoded automatic-teletype system. The German name for this high-level cryptographic system was Geheimschreiber; the British called it Fish. Some feared it would in part replace the Enigma system. The British had built a machine to help break into Fish that was so complicated in appearance that it was christened “Robinson,” after Heath Robinson, the British version of the American cartoonist Rube Goldberg, who devised fantastic machines to perform ludicrous tasks. Beyond that, and far more importantly, they had commenced work on an experimental, mammoth new Fish bombe aptly named Colossus, which had 2,400 vacuum tubes!*

  During the summer of 1942, the British authorized the semipermanent attachment of two U.S. Navy officers to Hut 8, the naval cryptography section at Bletchley Park—reservist Joseph J. Eachus and Robert Bellville Ely, III. In a history of the U.S. Navy bombe project, its chief designer, Howard T. Engstrom,† wrote that Ely and Eachus were sent to England in July of 1942