Battle of Atlantic , June-July Patrols in North Atlantic , 1941

Hitler’s U-Boat War - Clay Blair Jr

The Bismarck affair had disrupted the U-boat patrol cycles in the Atlantic and gutted the western patrol line south of Greenland. By June 1, the line consisted of merely four boats. However, seven of the twenty boats that sailed in June were en route to reinforce it, plus U-557, which had withdrawn, temporarily, to refuel from the scuttled Bismarck supply ship Belchen. At the request of the OKM, two other new VIIs sailing from Germany to join the patrol line, U-79 and U-559, were temporarily diverted to the Denmark Strait to assist in a proposed sortie of the “pocket” battleship Lützow (ex-Deutschland). However Royal Navy and RAF acted first. Probably acting on Enigma intelligence , fourteen RAF Coastal Command Bristol Beufort torpedo bombers attacked pocket batleship Lutzow at Norwegian waters on 13th June and scored a torpedo on Lutzow and badly damaged her that she remained in shipyard for seven months for repair.

Positioned beyond range of ASW aircraft based in Iceland or Newfoundland and close enough to Belchen for refueling, Dönitz expected great results from the western patrol line. But problems arose. Belchen was lost almost immediately and Korth’s U-93 took Belchen’s survivors to Lorient. In addition, another boat, Richard Zapp’s new IXB, U-66, lost all four of its torpedo-tube bow caps and aborted—unnecessarily soon, Dönitz logged. The remaining ten boats, thinly spread across possible convoy routes, were bedeviled by heavy fog, caused when cold Arctic air masses met the warm waters of the Gulf Stream.

From Ultra the British Admiralty knew the approximate position and strength of the U-boat patrol line. Working in close harmony, Rodger Winn in the U-boat Tracking Room and officials of the Admiralty Trade Division and those at Derby House in Liverpool routed the eastbound Halifax convoys well around the line. Thus the only ships the boats encountered were the (mostly empty) unescorted westbound singles or doubles, which had dispersed from the outbound convoys west of Iceland before the “end-to-end” escort came into being.

Although the patrol line found no Halifax convoys, the boats encountered and continued to sink a number of westbound singles and doubles. The top shooter was the Ritterkreuz holder
Herbert Schultze, who was taking the famous but weary U-48 home to the Training Command. In merely nine days, Schultze sank five ships for 38,462 tons, including three tankers: the 9,500-ton British Inversuir, the 6,000-ton British Wellfield, and the 10,700-ton Dutch Pendrecht. This tonnage put Schultze over the 200,000-ton mark and Dönitz awarded him Oak Leaves to his Ritterkreuz, the fourth skipper after Prien, Kretschmer, and Schepke to earn that high honor in the North Atlantic.* Schultze left U-48 in Germany and returned to France to command the 3d Combat Flotilla at La Pallice.

No less aggressive was the Ritterkreuz holder Engelbert Endrass in the equally weary VIIB U-46. But he was bedeviled by torpedo failures—four, he reported. On June 2 and 6, he attacked and hit a freighter and a tanker, but each time the torpedo failed to detonate. On June 8 he simultaneously attacked a tanker and a freighter. Two more torpedoes failed to detonate, but nonetheless Endrass damaged the 6,200-ton British tanker Ensis and sank a 5,300-ton freighter. In retaliation, Ensis turned on U-46 and rammed her, knocking out the attack periscope. Endrass put Ensis under with a finishing shot, then aborted to France. Inbound to Lorient he sank a 5,600-ton freighter by torpedo and gun. His overclaims of 16,500 tons sunk also put Endrass beyond the 200,000-ton mark and he, too, was awarded Oak Leaves to his Ritterkreuz.

Another Ritterkreuz holder, Wolfgang Lüth in the old but recently rehabilitated Type IX U-43, replaced Endrass in the patrol line. He sank two ships for 7,500 tons, but U-43 was not really combat-worthy. When Lüth returned to Lorient, the boat went back into the yard for another overhaul, to remain there until November, having completed only two war patrols in twelve months, during which Lüth sank only five ships. The other skippers of the patrol line—some on maiden voyages—sank another fourteen ships between June 1 and June 18. The most successful of these was Klaus Scholtz in the Type IXB U-108, making his third Atlantic patrol. He claimed sinking four ships for 27,300 tons, including a 14,000-ton auxiliary cruiser. In reality he sank four freighters for 17,000 tons.

Erich Topp in U-552, who had made three patrols to North Channel in the duck U-57 and two in U-552, requested that dangerous area again. In view of the fact that the duck U-141, on indoctrination patrol, had been severely damaged there in recent days, Dönitz was hesitant, especially since the shortest nights of the year were fast approaching. Finally, Dönitz consented.

The plan was for Topp to coordinate operations, if possible, with three Type IID ducks on indoctrination patrols close to the British Isles: the U-141, repaired in Lorient; the U-143, sailing from Germany; and the U-147, which had earlier sailed from Germany. Unknown to Dönitz, the U-147, commanded by Eberhard Wetjen, had been sunk on June 2 by British warships, the destroyer HMS Wanderer and corvette HMS Periwinkle, following Wetjen’s bold solo attack on convoy Outbound 329.

Topp found the area teeming with ASW aircraft, forcing him to crash-dive up to ten times a day, a nerve-racking routine during which several of his men broke down. Nonetheless, he found and sank three ships for 24,400 tons, including the 11,000-ton British freighter Norfolk. These sinkings brought Topp’s claims to 100,000 tons, earning him a Ritterkreuz. On June 18, Topp came upon an inbound convoy and attempted to attack and bring in the ducks and other boats, but the escorts drove him off. The duck U-141 was unable to cooperate with U-552 but she shot at two ships, sinking one.

Another duck, the U-138, commanded by twenty-five-year-old Franz Gramitsky, who had served in combat under Schepke and Lüth on other ducks, had arrived in Lorient from Germany for a top-secret special mission. Gramitsky was to penetrate the mined British naval base at Gibraltar for the specific purpose of sinking the battleship Renown or an aircraft carrier or, at the very least, a heavy cruiser. Should he succeed in sinking a capital ship—as Prien had at Scapa Flow—he was assured of a Ritterkreuz. Should he run into difficulty, the crew was to scuttle and swim to Spain, where it was to be assisted in making its way back to Lorient.

Gramitsky sailed from Lorient on June 12. Other than he, no one on the boat knew the purpose of the mission. Early on the morning of June 18, when U-138 was about 100 miles west of the Strait of Gibraltar, inbound on the surface, the bridge watch spotted what was believed to be a “cruiser” and dived. Actually, the “cruiser” was the destroyer HMS Faulkner, which in company with four sister ships of the 13th Destroyer Flotilla, HMS Fearless, HMS Forester, HMS Foresight, and HMS Foxhound, was conducting a sonar sweep, probably forewarned by Ultra to be on the lookout for U-138. The skilled sonar teams on HMS Faulkner and HMS Forester had helped kill the first U-boats of the war, U-27 and U-39.

HMS Faulkner obtained sonar contact on U-138 and attacked immediately, dropping six depth charges set for 100 to 250 feet. These exploded with uncanny accuracy, wrecking and flooding the uboat. Out of control, her internal spaces awash with water, she twice slid down to 650 feet before Gramitsky could blow her ballast tanks and get her to the surface. When she popped up, the entire crew jumped overboard. HMS Forester saw the doomed boat on the surface and attacked with guns. She dropped six more close depth charges before she realized U-138 was already sinking, vertically, stern first. HMS Faulkner fished out the entire crew of twenty-eight men; there were no serious casualties.

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To June 18, none of the boats on the distant western patrol line had seen any sign of a Halifax convoy. “The lull in traffic … is striking,” Dönitz logged. He decided to move the line southeastward, to “mislead” the enemy, in case they “had knowledge of the patrol line.” At the same time, he directed Kleinschmidt in U-111, the northernmost boat in the line, to return to the ice pack off Newfoundland, to see if the convoys were sailing far to the north. The shift to the southeast produced no results. On June 19, therefore, Dönitz disbanded the patrol line and scattered the twenty boats in the North Atlantic to positions within a huge rectangle, measuring roughly 1,000 by 1,800 miles. The twenty boats included the new VIICs U-79 and U-559, which had been assigned to the Denmark Strait to support the aborted Lützow sortie, but U-559 had bent her periscopes in the ice and was forced to head for Lorient.

While westbound to her designated station, shortly after midnight on June 20, the new VIIC, U-203, commanded by Rolf Mützelburg, age twenty-eight, from the duck U-10, sighted a battleship, escorted by a single destroyer. She was the aged USS Texas, part of a temporary United States naval task force that included the other two old battleships, USS New York and USS Arkansas, all deployed to help the British intercept the anticipated sortie of Lützow. Since USS Texas was then about 800 miles south-southwest of Iceland and ten miles inside a zone in which Hitler had authorized attacks on neutral warships, Mützelburg boldly went to battle stations and chased the zigzagging giant northeast, wondering if USS Texas (like the fifty destroyers and ten Coast Guard cutters) had been loaned, sold, or given to Great Britain. But USS Texas was making high speed and after a sixteen-hour pursuit that took the vessels 148 miles inside the zone, Mützelburg had to give it up, a great disappointment.

Later in the day, when Mützelburg reported his unsuccessful chase, it caused a great stir in Kerneval and Berlin. D day for Operation Barbarossa was merely forty-eight hours away; Hitler had made it clear that U-boats and merchant-ship raiders were to avoid incidents with United States vessels. And yet the appearance of Texas within the “German zone” was a defiant challenge. Since Dönitz and Raeder and others at the OKM believed Germany should not show weakness lest the United States transgress further, they concluded that Mützelburg had acted correctly in attempting to attack Texas, and Raeder so informed Hitler, who was in “complete agreement.” However, since errors in navigation were more the rule than the exception, it was also agreed that no action against neutral (i.e., American) warships was to be taken within twenty miles of the German boundary line, and Dönitz so informed the boats.

Later that night, June 21–22, Hitler personally telephoned Raeder to nullify the new policy. During Barbarossa, Hitler stated, attacks on American warships anywhere in the German zone were not to be undertaken. “Until there is a clear development of the Barbarossa campaign,” the OKM logged, Hitler “desires that all incidents with the U.S.A. be avoided.” Hitler himself “will decide when attacks on U.S.A. warships are again to be permitted.”

Dönitz relayed the new policy to the boats on June 21: “The Führer has ordered, for the next few weeks, avoidance of any incident with the U.S.A. Proceed accordingly in any doubtful case.” As a further precaution, Hitler had ordered that the U-boats were to attack only clearly recognizable British cruisers, battleships, or aircraft carriers within and without the zone, bearing in mind that American ships in that category might be blacked out and should not be mistaken for British.

This order, Dönitz complained in his memoirs, created “a situation which was unique in the history of war.” It meant that “U-boats could no longer attack their most dangerous enemies, the destroyers, frigates, and corvettes, whether British or any other nationality. … The British antisubmarine forces thus had a completely free hand.” But this was splitting hairs. Because of the shallow torpedo settings required and the resulting erratic performance, U-boats did not customarily attack convoy escorts. They avoided and evaded escorts and when counterattacked by escorts, they went deep. And yet it rankled to be restricted from attacking escorts, and Dönitz did not hesitate to make his views known to the OKM.

Returning to his designated patrol area, on the afternoon of June 23—the second day of Barbarossa—Mützelburg in U-203 happened upon convoy Halifax HX 133 at longitude 41 degrees west—400 miles due south of Greenland. His contact report galvanized Kerneval; it was the first Halifax convoy any U-boat had found in thirty-five days. Since it had a very long way to go, there was a good possibility that ten or more boats could be brought up to attack it along its track. Accordingly, Dönitz instructed Mützelburg to shadow and radio beacon signals for the benefit of the other boats, thus launching an epic chase and battle.

Initially composed of forty-nine ships laden with valuable cargos, Halifax 133 had sailed on June 21. It was the fifth eastbound transatlantic convoy to be provided “end-to-end” or “clear-across” escort and to sail at increased speed to accommodate the 12- to 15-knot ships that therefore had been sailing outside convoys. A newly formed Canadian escort group (the destroyer HMCS Ottawa and four corvettes, three Canadian and one British) was to take the convoy east to 35 degrees west, where an Iceland-based British escort group was to shepherd it through the middle leg to about 20 degrees west. In a reverse process, another Canadian escort group (corvette HMCS Wetaskiwin and four other corvettes), sailing from Iceland, was to relieve a British escort group at 35 degrees west and shepherd convoy Outbound OB 336 onward to Canada.

Mützelburg in U-203 tracked Halifax HX 133 throughout the afternoon and evening of June 23, sending frequent reports. All over the ocean the widely scattered boats plotted the positions by the new “reference point” system and calculated the chances of making an interception. After two other new VIICs, U-79 and U-371, had made contact and reported, in the early hours of June 24 Dönitz authorized U-203 to attack.

In his first salvo of the war, Mützelburg fired at three large ships. He claimed that two sank, but only the 4,400-ton Norwegian freighter Solöy was confirmed. Heinrich Driver, age twenty-eight, in the new U-371, attacked next, sinking the 4,800-ton Norwegian freighter Vigrid, which was straggling. The crew and ten American Red Cross nurses launched four lifeboats. Two boats headed for Greenland, the other two for Ireland. Wolfgang Kaufmann, age twenty-nine, in the new U-79 had no opportunity to shoot, but he shadowed and reported. The destroyer HMCS Ottawa, commanded by Edmond R. Mainguy, and the four corvettes of the Canadian escort group, engaged in the “first Canadian Navy convoy battle,” sped hither and yon, unable to communicate and dropping depth charges to little purpose.

At that time, two consecutive convoys, Outbound OB 335 and Outbound OB 336, were proceeding westward in this area. Noting that Outbound OB 336, composed of twenty-three ships and guarded by a Canadian escort group of five corvettes, was to pass close to the besieged Halifax 133, Western Approaches ordered the convoy commander to alter course to avoid that area. The convoy commander’s regular radio operator was ill; his substitute, who could not decode the message, mindlessly filed it away. A similar message was sent to the flagship of the Canadian escort group, corvette HMCS Wetaskiwin, but the Canadians had not yet found the convoy and the message could not be delivered. Thus Outbound OB 336 continued on a converging course with eastbound Halifax HX 133, bringing together a total of sixty-five merchant ships and two newly formed Canadian escort groups. Later on the morning of June 24, about seven hours after his attack on Halifax HX 133, Mützelburg in U-203 made contact with Outbound OB 336. The operational orders required that Mützelburg report the convoy so Kerneval could bring up other boats, withholding an attack until authorized. But Mützelburg impulsively assaulted the formation, sinking two freighters, the 5,000-ton British Kinross and the 2,000-ton Dutch Schie. Later that afternoon, he reported this new convoy and the upsetting news that he had already attacked it and that owing to a broken muffler valve he was aborting immediately—before any other boats could make contact. Dönitz angrily ordered Mützelburg to shadow and report, but he had lost contact and could not comply.

From Mützelburg’s reports, and others, Dönitz realized that two convoys were passing “in a narrow area,” and there was an opportunity for a slaughter. He therefore passed along all information and instructed the converging boats to attack whichever convoy they considered “most favorable.” At the same time, Western Approaches, seeking to protect the most valuable (eastbound) ships, ordered the Canadian Wetaskiwin group, still searching for Outbound 336, and five of the British escorts with convoys Outbound OB 335 and Outbound OB 336, to reinforce the eastbound Halifax HX 133.

By the time these orders were received, the Wetaskiwin group had picked up the distress calls from and the position of the long-sought Outbound 336. Contrary to orders of Western Approaches, the leader of HMCS Wetaskiwin group, Guy S. Windeyer, elected to divide his force so that Outbound OB 336 would not be completely unprotected. He sent two corvettes to Halifax HX 133 and attached Wetaskiwin and two other corvettes to Outbound 336. His disobedience of a direct order was to evoke criticism—and ridicule—of the Canadian Navy, but upon investigation at a later date, Derby House approved of the decision. However, by the time the Wetaskiwin group finally caught up to the convoy, it had dispersed into a dense fog and the group could not provide meaningful support.

About six U-boats elected to pursue this dispersing convoy. These included two experienced skippers, Ernst Mengersen in U-101 and Klaus Scholtz in U-108. But all the U-boats were hampered by fog and fuel shortages. Only Scholtz in U-108 sank a ship, the 4,400-ton Greek Nicolas Pateras.

During the daylight hours of June 24, Wolfgang Kaufmann in the new U-79 continued to track the eastbound Halifax 133. Early that evening Peter Lohmeyer, age thirty, a merchant marine veteran who had trained on the recently sunk duck U-138, came up in his new VIIC U-651 and attacked three ships. He claimed sinking all three, but only one, the 5,300-ton British freighter Brockley Hill, went down. The Canadian escorts counterattacked in confusion, again to no purpose. After Lohmeyer’s attack, the British corvette HMS Gladiolus from Outbound OB 335 and four other escorts from Outbound 336 arrived, raising the total escort force with Halifax HX 133 to ten. Shortly after midnight, June 25, Gladiolus saw a U-boat speeding very close across her bow. This was Walter Flachsenberg, age thirty-two, in another new VIIC, U-71, boldly but unalertly maneuvering to attack the rear of the convoy. HMS Gladiolus put on full speed to ram but, when it was realized on second thought that HMS Gladiolus was 600 miles from land and might sink herself in the ramming, the collision was aborted, giving U-71 time to crash dive. HMS Gladiolus got a firm sonar contact and carried out five separate attacks, dropping thirty depth charges. The recently arrived British corvette Nasturtium joined HMS Gladiolus, which was nearly out of depth charges, and dropped six. A half hour later, U-71, severely damaged internally, surfaced to escape in the darkness. Seeing her, HMS Gladiolus opened fire, but could not use her 4″ gun because Nasturtium was in the way. When she cleared out, HMS Gladiolus brought her gun to bear and claimed a fatal “direct hit” on the conning tower. Although HMS Gladiolus was criticized for not ramming the boat in the first attack, she was credited with a kill in the second attack. In fact, Flachsenberg got U-71 away, aborting to Lorient with severe damage.* Dönitz heaped praise on Flachsenberg for extricating U-71 from “a very difficult situation.”

Surrounded by ten escorts, convoy Halifax HX 133 proceeded eastward on June 26. At nightfall, a half dozen U-boats moved in for the kill. Wolfgang Kaufmann, the patient shadower in the new U-79, hit and damaged a 10,400-ton British tanker, but she kept on going. Erich Topp in U-552, who had come west from the North Channel area and was low on fuel and torpedoes, hit a freighter, but the torpedo failed to detonate. Owing to his shortage of fuel, Topp was forced to return to Lorient. Another new VIIC, U-562, commanded by Herwig Collmann, age twenty-five, which had only just arrived in the Atlantic, tried to attack but was driven off. Yet another new VIIC, U-564, commanded by Reinhard Suhren, who had won a Ritterkreuz while serving as first watch officer on the famous U-48, attacked and hit three big ships in one amazing salvo: the 8,800-ton Dutch freighter Maasdam, the 8,700-ton British freighter Malaya II, and the 9,500-ton Norwegian tanker Kongsgaard. The Maasdam sank. She had on board a company of American Marines en route to the American Embassy in London. Rescue ships took the Marines to Iceland. The Malaya II, carrying a load of ammunition, blew up with a horrific blast. The Kongsgaard was damaged but she kept going.

Another VIIC, U-556, commanded by the Ritterkreuz holder Herbert Wohlfarth, fresh from Lorient on his second patrol, joined the attackers in the early hours of June 27. Notwithstanding a noisy coupling in his port motor, Wohlfarth decided to attack submerged during daylight and pulled ahead of the convoy and dived. Before he could shoot, the British corvette HMS Nasturtium got U-556 on sonar and fired off all her remaining twenty depth charges. Responding to her alarm, the British corvettes HMS Celandine and HMS Gladiolus came up, but when neither could get a sonar return, they expressed doubt about the contact. Insisting she had a good contact, HMS Nasturtium guided HMS Celandine to the likely spot. HMS Celandine dropped twenty-four charges, to no apparent effect. Still skeptical of this “contact,” both HMS Celandine and HMS Gladiolus repeatedly expressed doubt, but finally HMS Gladiolus, too, got a contact and made a ten-charge attack, which brought up a large oil patch.

The charges from HMS Nasturtium, HMS Celandine, and Gladiolus had, in fact, severely damaged U-556. Wohlfarth shut down the noisy port motor but heavy flooding aft short-circuited the starboard motor, forcing him to restart the port motor. However, the flooding aft continued to the point that Wohlfarth lost control of the boat, which slipped down to 426 feet. Believing his only chance of survival lay in surfacing to attack the corvettes (in violation of Hitler’s orders), Wohlfarth blew ballast tanks and came up almost beneath Gladiolus, which was in the process of firing three of her last ten depth charges. One of these actually hit the aft deck of U-556 and bounced off. HMS Gladiolus, HMS Nasturtium, and HMS Celandine opened fire at point-blank range with 4″ guns, scoring hits on U-556’s conning tower. The gunfire killed some Germans and persuaded Wohlfarth to scuttle and abandon ship. Believing there was a chance to capture U-556, HMS Gladiolus launched a whaler with a boarding party, led by Lieutenant J. G. Gifford-Hull, who fished out a “German officer” to “help.” However, upon entering the conning tower, the British sailors saw that the control room was flooded and smelled chlorine gas. Since U-556 was obviously going down fast, Gifford-Hull abandoned the attempt to capture her, coming away only with a torpedo-maintenance booklet and a Very pistol.

Meanwhile, HMS Gladiolus picked up Wohlfarth and thirty-nine of his crew. Four Germans died in the sinking; another died from inhaling toxic gas in his escape apparatus. Wohlfarth was the sixth Ritterkreuz holder to fall, the third to be captured.* British interrogators did not rate the crew highly. Except for Wohlfarth and a few capable and experienced chiefs and petty officers who had earlier served with him, the senior officers and men, the interrogators reported, were “unreliable” newcomers “of limited experience” who had been “hastily promoted.” The junior men were “decidedly poor stuff.”

That afternoon there was a change-up in the escorts of Halifax HX 133. The Canadian group (the destroyer HMCS Ottawa, five corvettes) peeled off and went into Iceland, where it was criticized—and even ridiculed—for “losing” five ships of the convoy and accomplishing nothing in return. It was replaced at sea by C. D. Howard-Johnston’s British Escort Group 12, bringing the total escorts for the final leg to thirteen.

The U-boats continued to track and attack Halifax HX 133. In the early hours of June 29, Peter Lohmeyer in the new U-651 caught up again after a four-day chase. Closing submerged, he fired two torpedoes and hit the 6,300-ton British freighter Grayburn, the convoy flagship, which was loaded with 10,000 tons of steel. It sank in four minutes. But the next ship in the column, the 8,000-ton British tanker Anadara, plowed into the submerged U-651 with a heavy jolt that threw the boat out of control and weakened seams.

The more battle-wise warships of Escort Group 12 deployed in a fighting mood. As a deterrent they first dropped depth charges at random. However, two escorts, (HMS destroyer Scimitar, minesweeper HMS Speedwell) soon reported firm sonar contacts and they conducted deliberate attacks. Some of the depth charges fell close to U-651, doubtless opening seams weakened by the collision with Anadara. Flooding aft, U-651 slid down to 525 feet and Lohmeyer exhausted his battery in a vain effort to regain control of the boat with the motors. In a last desperate effort to escape on the diesels, he blew all ballast tanks and surfaced.

When Lohmeyer lit off the diesels they emitted small puffs of black smoke. The destroyer HMS Malcolm saw the smoke six miles off, gave the alarm, and charged in, firing her main batteries. Four other escorts, including the destroyer HMS Scimitar and corvette HMS Nasturtium, came up, firing guns. In the face of the fire, Lohmeyer scuttled and abandoned ship. Rigging scramble nets, HMS Malcolm picked up Lohmeyer and all forty-four of his men, but HMS Scimitar closed HMS Malcolm and snatched one of the Germans from the net. The Admiralty credited Escort Group 12 with the kill, but in later years, Admiralty historians withdrew the credit and bestowed it upon Anadara, which retroactively became the first merchant ship to be credited with sinking a U-boat.

As the convoy drew closer to the heavily patrolled Northwest Approaches, Dönitz called off the boats, directed them elsewhere, and asked for reports. He calculated that in all, about fourteen U-boats had made contact with Halifax HX 133, including four more new boats from Germany which joined near the end of the chase. The confirmed results were shockingly low for Germans: five U-boats sank six ships for 38,000 tons* and damaged two tankers, Tibia and Kongsgaard. In return, two boats; U-556 and U-651, had been lost, and U-71 very nearly lost, a ruinous “exchange rate” of three ships sunk for each boat lost. Two boats had sunk three ships for 11,300 tons from convoy Outbound OB 336. Grand total: nine ships for 49,300 tons, three of them by Mützelburg in U-203, who, Dönitz logged, conceded his “mistake” in launching an impulsive attack on Outbound OB 336 and of aborting before any other boats arrived.

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The battle with Halifax HX 133 led to important changes in the U-boat strategy and tactics, including, most notably, a withdrawal of the boats from the Greenland area to more easterly hunting grounds. The reasons were several:

• Although the ocean west of Iceland and south of Greenland was still devoid of ASW aircraft and experienced escorts and was therefore safer for U-boat operations, the area was simply too large for effective convoy hunting by patrol lines with the few boats then available. The U-203 discovered convoy Halifax 133 only after Dönitz had disbanded the western patrol line and scattered the boats over a huge area. But in scattering the boats, Dönitz foreswore the ability to quickly bring them up for a pack attack—to mass maximum strength at the point of contact with the enemy.

• Operations in this very distant area were extremely difficult for the relatively short-ranged Type VII boats. The fuel expended going out and back left little for patrolling the area for any appreciable time, or for confidently engaging in extended convoy chases. Apart from that, the expenditure of all torpedoes or a simple mechanical failure—such as U-203’s defective muffler valve—forced a costly termination of the patrol. Until the U-tankers, or “supply boats,” which were still under construction,* became operational and the Type VIIs could be replenished and obtain medical help and spare parts at sea, thus greatly extending time on patrol station and reducing the number of aborts, operations in the Greenland area were simply not efficient.

• The higher speed of Halifax convoys posed great difficulties for the U-boats. The Type VIIs had a maximum (engine-straining) speed of 17 knots; the Type IXs, 18 knots. Unless held down by surface or air escorts, the boats could shadow effectively, but to overtake even a zigzagging fast Halifax convoy to gain favorable shooting positions from ahead or the flanks required much time (as well as fuel), increasing the chances of being discovered and counterattacked by escorts and thus losing the element of surprise.

• The weather conditions and the onset of the summer solstice were not favorable for U-boat operations in the Greenland area. Returning boats reported dense, blinding fog during half the patrol days. The fog restricted not only reconnaissance but also navigation (by sun and star sights), leaving many skippers with only a vague idea of where they were. When not fogbound, the very long days—and very short nights—in those north latitudes restricted the available hours for night surface attacks, when the boat was most effective and mobile, and compelled skippers to resort in many instances to submerged daylight attacks, when the boat was least mobile and most vulnerable to sonar detection.

The British sailed 383 loaded ships in convoys from Halifax and Sydney to the British Isles in the month of June. The U-boats found only one convoy that month, Halifax 133, from which they sank six loaded ships of the forty-nine. No other loaded eastbound ship from Canada fell victim to the U-boats in June; hence 377 loaded ships (or about 99 percent) reached destinations. In the first two weeks of June, before convoying on the Iceland-Canada leg was fully in effect, the U-boats had better luck in sinking singles, most of them empty ships from disbursing Outbound convoys south of Greenland. They destroyed twenty-two such singles, plus two from convoy Outbound OB 336, a total of twenty-four empty ships for 134,754 tons. In the second two weeks, after the Iceland-Canada leg was afforded better protection by the Canadian escort groups and aircraft and the Halifax convoy speed was increased to accommodate the 12- to 15-knot vessels, the U-boats sank only five singles in that area.*

The failure of the U-boats to find eastbound convoys in the North Atlantic and to inflict greater damage on the only one they found, Halifax HX 133, and Dönitz’s decision to withdraw the boats from the Greenland area, was a clear victory of the British defense over German offense. It was due, in part, to radio intelligence (Ultra, DFing, Traffic Analysis, RFP, TINA), which enabled the Royal Navy to sink the supply ship Belchen and to divert most convoys around the U-boat patrol lines; in part to the initiation of “end-to-end” surface escorts (however green the Canadians) and air escort from Newfoundland and Iceland; in part to the higher speed of the Halifax convoys, in part to the inability of the boats to operate effectively in far western areas, and in no small part to the steady decline in the experience level of the U-boat skippers and crews. Not for sixteen more months (October 1942) did the U-boats again inflict any appreciable damage on a Halifax convoy.

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