Engineers of Victory

by Paul Kennedy

  But what if the convoys were better protected and the British could see as well as the Germans? Then things were greatly different. Consider, for example, the situation during mid-May 1943 in which each side was rather smartly reading the other’s traffic and sending the new intelligence to its forces at sea. By the time of the great battles (May 7–14) around convoys HX 237 and SC 129, the intelligence war had reached a remarkable level of sophistication, of point and counterpoint, so that neither side had the lead for very long. The same was true a week later with regard to the fighting that surrounded convoy HX 239, coming from Halifax to the Clyde. First, B-Dienst detected the location and course of this large group of merchantmen. Shortly afterward, the British cryptographers read Doenitz’s Shark instructions for a wolf pack ambush, so Western Approaches Command ordered the convoys to alter course. But B-Dienst then read those signals and redirected the U-boat lines—no fewer than twenty-two submarines—to attacking positions. Unfortunately for the U-boats, however, at that point they met the massed forces of Allied air- and sea power over the Atlantic. The new escort carrier USS Bogue destroyed U 569, while HMS Archer’s aircraft, now fitted with rockets, sank U 752. No merchant ships were lost.39 The plain fact was that Ultra assisted in but could never win the hard-fought convoy battles. When the British decision was made to fight the convoys through the U-boat lines, victory went to the side with the smartest and most powerful weaponry, not the one with the better decrypts.

  We can now understand how these great advances in the Allied systems of detection and destruction interacted with the two other factors mentioned above: numbers and morale. When, in mid-March 1943, HMS Volunteer was the only escorting warship with convoy HX 229 to possess HF-DF, and when its radio operators had time either for detection of U-boats or for receipt of Admiralty orders but not both, its potential was limited. When, about six months later, all escorts were fitted with HF-DF, the Allies gained a huge advantage, as they did also with the coming of short-range radio between warships. Similarly, when there were just a few hard-stretched aircraft operating for only several hours each in the mid-Atlantic, the U-boats benefited enormously. When whole squadrons of very long-range aircraft were operating out of bases in the Shetlands, Northern Ireland, Iceland, Greenland, and Newfoundland (and, after mid-1943, the Azores), and when the Bay of Biscay could be patrolled all through the night by aircraft equipped with centimetric radar, Leigh Lights, depth charges, acoustic torpedoes, even rockets, Doenitz’s submarines knew no rest. A single escort carrier such as HMS Archer was a welcome sight to a convoy but could not affect the tactical balance very much. With a dozen escort carriers at sea, by late 1943, the whole situation had changed.

  It was small wonder, then, that the Ultra decrypts detected a sharp decline in the morale of the U-boat crews after the May 1943 battles; small wonder that Doenitz’s urgings sounded more desperate. While he possessed more submarines than at any previous time, fewer now pressed home their attacks, and more reported damage and returned to base. Many of their crews were taken into Allied captivity as their stricken boats slowly sank beneath the waves. Captain Herbert Werner, a U-boat commander himself throughout this long war, later wrote a moving memoir; his title, Iron Coffins, says it all.40

  A Few Final Blows

  The overwhelming importance of airpower received further confirmation during the next two phases of this history: the Allies’ aerial offensives in the Bay of Biscay and the failed U-boat attacks on the U.S. convoys to North Africa. These two battlefields were separate geographically, but the struggles unfolded in roughly the same months of 1943 and were in many ways coeval, for if the submarines tiptoeing westward past northern Spain could be destroyed en route, there would be fewer of them surviving to attack the U.S.-Gibraltar convoys or to range farther afield. And if the American escorts on the North African route could batter Doenitz’s wolf packs as savagely as the predominantly British and Canadian fleets had done earlier in the North Atlantic, there would be fewer submarines returning to French bases in any event.

  U-boats could cross the Bay of Biscay either on the surface or submerged, and by day or at night, and it was from this that their tactical-technical problem emerged. If they traveled submerged, their speed was much slower, their batteries drained faster (which certainly didn’t help crew morale), and they could still be picked up by the sonar of an enemy warship. On the other hand, if they traveled on the surface, they could reach the wide Atlantic waters faster, though with a much greater possibility of detection by enemy radar, and then they would be at serious risk of aerial as well as surface-vessel attack just when they were most vulnerable. Additionally, by the second half of 1943 Bletchley Park was much more successful at reading German naval codes, and more swiftly, than B-Dienst was in adjusting to the improved Allied ciphers.

  These problems were compounded by the fact that Allied aircraft and surface escorts had been transformed by the many technological innovations described above into horrifying submarine-killing machines. It was not just that the Allies were now deploying the new support groups of powerful sloops and fleet destroyers and the purpose-built escort carriers. It was also the case that the standard, rather plodding workhorses in the Allies’ armory, such as the Flower-class corvettes and the medium-range aircraft such as the Wellingtons, the Hudsons, and the Sunderlands, were being steadily improved. In 1940–41 the corvettes were underarmed, underequipped, and horrible sailors against the giant North Atlantic waves (one American observer thought their crews should get submariner’s pay because the vessels seemed to be more than half underwater much of the time). After 1943, those vessels, and the newer types of corvettes and frigates that gradually replaced them and were especially designed for the Atlantic, had much greater horsepower, better detection and destruction equipment, a raised bow, and much more space for the commander’s many functions. On larger vessels, one of the forward guns was now replaced by a Hedgehog; the depth charges were much more powerful and had improved timing devices; and the superstructure sprouted all sorts of antennae, not just the radio mast but the HF-DF and 10-centimeter equipment as well.

  The same metamorphosis was true of a Wellington, a sturdy but basic twin-engine bomber originally designed by Barnes Wallis for raids into the western parts of Germany. By 1943 it had, under RAF Coastal Command, become an amazing acoustic machine, spouting aerials along its spine, out of its side, and out of its nose. Its armaments could include forward-firing cannon, rockets, more efficient depth charges, even the new acoustic torpedoes. At night, when its radar brought it close enough to a U-boat on the surface, its massive Leigh Lights would go on, and then the mayhem against the submarines would begin.

  Doenitz was nothing if not a fighter, and the German shipyards were producing more U-boats than ever in 1943, which could still reach the Atlantic via roundabout routes through the Greenland-Iceland-Faroes gaps. Recognizing that Allied airpower was now key, Doenitz also persuaded Berlin in autumn 1943 to give his U-boats much more support in the Bay of Biscay than before. In fact, so seriously did the German air attacks upon Coastal Command’s antisubmarine squadrons become at that time that the RAF was compelled in turn to allocate Beaufighter and Mosquito night fighters to protect them. Moreover, a number of U-boats were equipped with far heavier antiaircraft guns, including four-barrel flak guns, for Doenitz was also encouraging his captains to fight it out on the surface if they could. Finally, the Luftwaffe itself was also being equipped with acoustic torpedoes, as were the newer submarines; in late August German aircraft made their first attacks with glider bombs on two of the escort groups.41

  Thus, apart from the reduction of attacks in the North Atlantic after June 1943, the fighting over the convoys was not getting any less hectic, nor the wolf packs any less dangerous. Individual actions were as wild as ever. One Sunderland, flying back home across the Bay of Biscay, was attacked by no fewer than eight Junkers Ju 88s, shot down three of them, and got back to land on the pebbles of Chesil Beach on three engines; the German nickn
ame for the Sunderland was “the flying porcupine.” A little later, a furious surface-to-air battle occurred between five U-boats traveling on the surface across the bay together and four Polish-flown Mosquitos. There were British, American, Australian, Polish, Canadian, and Czech squadrons in this phase of the fighting.42 Some of the planes crashed onto the U-boats, for the shoot-outs between two determined foes distinctly increased that possibility. Occasionally the survivors of any combination of merchantmen, escorts, aircraft, and U-boats might be in their lifeboats and rafts in the same waters and picked up by the same rescue ship. Ramming was common, and among some destroyer captains it seems almost to have been the preferred form of attack—they made sure they crushed the enemy vessel, and they probably also got three weeks of home leave for repairs as well.

  But the speed and ferocity of these episodes could not disguise the fact that “the Allied navies and air forces … at last enjoyed adequate strength in the right kinds of ships and aircraft, were trained to high efficiency and equipped with a comprehensive armory for finding and destroying U-boats.”43 Levels of training had been constantly racheted up, and in any case many of the Allied naval groups and air squadrons had by now considerable experience, which played to their advantage time and again. When a large battle developed in mid-October around convoys ON 206 and ONS 20, the merchantmen and close escorts were supported by no fewer than three highly competent Liberator squadrons (nos. 59, 86, and 120) and by a support group under Gretton, including, once again, Duncan, Vidette, Sunflower, Pink, and Loosestrife. One merchantman was lost, and five U-boats went to the bottom.

  Operating farther afield from close-escort support, Captain Johnny Walker and his 2nd Escort Group seem to have been given virtually a free hand to pursue his all-consuming passion: sinking U-boats, which they would sometimes stalk for days. By this time Walker had perfected his “creeping attack,” in which only one of his group kept its asdic sender/receiver on and then stayed at a fair distance from a submerged U-boat, whose captain was unaware that the other vessels, with their asdic switched off, were quietly coming right overhead, directed by radio from the control boat. On other occasions, Walker would have his sloops—HMS Starling, Wild Goose, Cygnet, Wren, Woodpecker, and Kite—advance in line abreast and drop their charges simultaneously, like an artillery barrage on land. Of the two schools of strategic thought about convoy warfare, Walker was definitely not of the just-get-the-merchantmen-home-safely persuasion. His operating instructions to the 2nd Escort Group, preserved after the war by the Captain Walker’s Old Boys Association in their home base of Liverpool, reads: “Our object is to kill, and all officers must fully develop the spirit of vicious offensive. No matter how many convoys we may shepherd through in safety, we shall have failed unless we slaughter U boats.”44 Walker was as good as his word. His little group sank no fewer than twenty U-boats from 1943 onward, and he himself gained an astonishing four DSOs before his premature death from exhaustion in 1944.

  Walker’s cat-and-mouse tactics were part of a larger Admiralty plan. It will be recalled how, during the convoy battles of early 1943, escort vessels such as Vidette and Pink had to keep giving up the pursuit of a submarine because of the dire need to return to guard their flocks. In the critical months of March through June 1943, the Admiralty’s Operational Research Department made a detailed statistical analysis of all the encounters between U-boats and Allied escorts over the previous two years.45 It found that if a warship went after a fast-submerging submarine for only a few attacks, the chances of the foe’s getting away were good. If the surface craft could remain in pursuit, perhaps losing but then regaining sonar contact an hour or so later, and especially if it could stay around to drop depth charges in six or more attacks over more than ninety minutes, then U-boat losses markedly increased. Here, then, was the statistical case for the creation of the support groups, at least if they remained in the general area of the convoys and did not go out hunting for a needle in a haystack. Horton recognized this all along, and it was only the overall shortage of surface warships that had prevented groups such as Walker’s being formed much earlier. But those Operational Research figures did pinpoint Doenitz’s dilemma in a stark way. His boats could stop the flow of Allied supplies to Europe only if they were willing to close with the convoys, but in so doing after July 1943, they were increasingly likely to be detected by aircraft and surface support groups, and hunted down to the end.

  If it was difficult, almost impossible, for the U-boats to deal with Walker, it was hardly less dangerous for them to go against the U.S. escort carrier groups on the Gibraltar and North Africa routes. Although the U.S. Navy had come into anti-U-boat warfare in a woefully unprepared state, it had learned fast (and despite the far larger calls upon its attention and resources from the Pacific War). By 1943 a stream of new, small, but powerful escort carriers was pouring out of the Tacoma, Washington, shipyards, their crews and aircrews going into intensive training, steaming through the Panama Canal, then forming the core of the escorts for the enormous numbers of American troops, munitions, and other supplies heading toward the Mediterranean theater as the invasions of Sicily and Italy developed. The first three of the Bogue class—USS Bogue itself, USS Core, and USS Card—had particularly aggressive and competent aircrews; in a sort of variant of Walker’s creeping attacks, two of their planes would strafe a U-boat on the surface, obscuring the fact that a third aircraft was approaching with bombs or homing torpedoes. Roskill’s official naval history records the USS Bogue’s aircraft sinking six U-boats on these 1943 Gibraltar runs, and the total kills achieved by the USS Card’s aircraft and close escorts was even higher: at least ten U-boats, perhaps an eleventh.46

  Overall, the escort carriers destroyed many fewer enemy submarines during the war than did land-based aircraft, yet their role in driving away U-boats from the North Atlantic convoys in the critical months of spring and early summer 1943 was great, and their protection of the flow of American troops and goods to North Africa and the Mediterranean was absolutely invaluable. Later in 1943, some escort carriers were detached to ambush U-boats meeting at refueling points in the Central Atlantic. Although British naval intelligence agonized about the risk of their Ultra source being detected—how many coincidences could there be of U.S. planes arriving in the bare oceans just when a U-boat was being refueled by the “milk cow” vessel?—the attacks certainly destroyed a disproportionately large share of refueling submarines, leaving the regular boats perilously low on supplies and forced to return to base early.

  From these dire trends the German submarine fleet could not recover. Though it resumed its attacks on Allied convoys in the first five months of 1944, including a renewed series of onslaughts upon the North Atlantic routes against the awful odds, it could never again achieve the success rate of its glory years of 1942 and early 1943. Its failure was evident, in spectacular form, on D-Day itself. There, as we shall see in chapter 4, the balance of forces—in the air, at sea, even on some of the contested beaches—was totally disproportionate. Not only were the German high command’s few Luftwaffe squadrons promptly destroyed, but the same was true of the Kriegsmarine’s “iron coffins”; Werner recounts how he and a group of highly experienced U-boat commanders, amazed at being held back in early June, were then ordered to attack the D-Day landings, including ramming an enemy ship like a kamikaze. Nothing could have been more remote from a submarine’s true vocation. Five of the eight U-boats so ordered were destroyed in such vain attacks; the other three limped back, damaged and ashamed.47 Allied control of the air and the waters was complete, and between June and August 1944 Doenitz’s submarines sank only five vessels during the greatest amphibious invasion of all time (one of those sunk, alas, was HMS Pink).

  But the failure of the U-boats to destroy, or even dent, Operation Overlord was not just a mark of an imbalance of power at the local, tactical level. It was also evidence that, whatever their earlier remarkable and sustained successes, the German submarines had failed to stop the giga
ntic surge of troops, munitions, fuel, food, and all the other vital goods being brought from the New World to the Old. The submarines had done their best—U-boat “aces” such as Kinzel were extraordinary fighters—but they had been beaten by a well-organized, multiple-armed counterattack in the middle of 1943. Because of the new Allied strengths, the convoys were getting through, increasingly unscathed; because they were unscathed, the island fortress of Great Britain was turned into an enormous launchpad for the invasion of Europe; and because that invasion took place without severe (or even much) disruption and the Allied armies could push ahead and into the Third Reich, the days of the U-boats were numbered. Their home bases, whether in western France or northern Germany, would be captured from the landward side.

  It is true that the German military-industrial complex was, in 1944 and early 1945, still pouring out dozens and dozens of newer, larger U-boats. Moreover, German scientists were working on some remarkably advanced types of U-boat (Hellmuth Walter’s brilliant designs, and the Type XXI “elektro-Booten”), which concerned the Admiralty all through the last year of the war in Europe. Doenitz’s U-boat fleet was still receiving and sending new boats out as late as April 1945, despite the more intensive Allied bombing of their construction yards and railway supply routes. The German submarines fought to the very end, impressively and ferociously. Since they made little impression upon the ceaseless flow of men and munitions across the Atlantic—and by the autumn of 1944 the new U.S. divisions could sail directly to France—their story fades into the background in most histories of the Second World War. Yet the period from January to April 1945 witnessed some of the fiercest duels ever between the U-boats and their long-lasting foes, RAF Coastal Command, the Royal Navy, and their Canadian equivalents.