Battle of Atlantic - April 1941 , Partial Compensation of Lack of North Atlantic Targets by attack on Allied shipping off Africa

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from “Hitler’s U-Boat War” , Clay Blair Jr
“The War for the Seas” - Ewan Madsley
“Hitler’s U-Boat War” David Mason
“Atlantic Campaign” Van der Vat
“Donitz , The Last Fuhrer” - Peter Padfield
“Donitz andthe Wolfpacks” - Bernard Ireland

U-BOAT ATTACK ON WEST AFRICA

In the beginning of March 1941 , Donitz and BdU command decided to strike Allied shipping lanes off West Africa especially vital convoy gathering and shipping hub at Freetown port at Sierra Leone where Royal Navy defences were much more weaker than North Atlantic where heavy U-*Boat losses in March 1941 brought diappointing results for German Navy.

In striking contrast to the boats in the north, the three Type IXB U-Boats enjoying better weather in the south continued to do very well. Off Freetown, on March 16, Jürgen Oesten in U-106 made contact with another convoy, (Sierra Leone) SL68, en route to Britain. Oesten radioed an alarm and beacon signals to bring up Georg Schewe in U-105, then attacked, sinking a 6,800-ton freighter. Mounting a second attack on the next night, Oesten claimed sinking three freighters for 21,000 tons and damage to another. Schewe in U-105 made contact, and over the next three days, March 18 to March 21, the two boats chewed away at the convoy, until all fourteen internal torpedoes on each boat had been expended. Schewe sank four ships for 25,500 tons; Oesten in U-106 claimed one “freighter” sunk, one damaged. Unknown to Oesten, the “freighter” claimed as sunk was actually Queen Elisabeth class battleship HMS Malaya, which was escorting the convoy. Slightly damaged, HMS Malaya limped across the Atlantic to the island of Trinidad, thence to the United States, where, as related, under the provisions of Lend-Lease, she was repaired and refitted along with the battleship HMS Resolution, which had been badly damaged by the Vichy French submarine Beveziers in the abortive Allied attack on Dakar.

Schewe and Oesten reported great success. In seven days of tenacious attacks, Schewe claimed sinking six ships for 41,000 tons, Oesten five ships for 36,000 tons—a total of eleven ships for 77,000 tons. The confirmed score was less: Schewe five ships for 27,000 tons, Oesten three ships for 17,000 tons—a total of eight ships for 44,000 tons, plus Oesten’s hit on Malaya, which put her out of action for months.

Winston Churchill was especially shocked and enraged by the losses in this convoy. In a “rocket” to First Sea Lord Dudley Pound he expressed his displeasure and criticized the absence of destroyers in the escort, especially since Malaya was in the formation. Pound replied that the destroyers at hand did not have sufficient range to sail with Sierra Leone convoys, and refueling at sea was deemed to be too dangerous since the ships involved involved were virtually unmaneuverable during the process. To this Churchill responded: “Nonsense!” If there were four destroyers present, three could protect the other one while it refueled from a tanker in the convoy.

The third IXB in southern waters, Georg-Wilhelm Schulz’s U-124, attempted to rejoin the others after resupplying from German auxilary raider Kormoran (which would close her career off Australia coast in a spectacular way in November 1941) , but she had a catastrophic failure in both engines, which left her helpless. After the engines were repaired, she closed the coast of Africa and sank a lone 3,800-ton British freighter, bringing Schulz’s total credited sinkings, including substantial overclaims, to 100,117 tons, earning him a Ritterkreuz. While Schulz was closing on Freetown, Schewe in U-105 and Oesten in U-106 downloaded deck torpedoes and then hauled westward and resupplied from Kormoran and the supply ship Nordmark, respectively. En route to the rendezvous, Oesten claimed sinking a 5,000-ton freighter, bringing his total claims to about 82,000 tons. Having heard from B-dienst that Oesten had hit Malaya, Dönitz awarded him a Ritterkreuz.

To then Dönitz, unshakably convinced that the decisive naval battleground lay along the convoy routes in the Northwest Approaches—between Iceland and the British Isles—had resisted to the utmost any “diversion” of U-boats from that area. But the poor returns and the loss of five boats to “obscure” (i.e., unexplained) causes (three of them commanded by his most experienced and notable skippers) led him to a profound decision: He would withdraw all U-boats from that rich target area for the time being and disperse them to more distant areas where British ASW was less intense, such as the waters west of Iceland and in the South Atlantic. This little-noted decision was a milestone in the U-boat war against the British Empire: the first clear-cut defeat for the German submarines.

The principal reason for that defeat was the paucity of U-boats. Counting all gains and losses, at the end of March 1941, Dönitz still controlled only twenty-seven combat-ready oceangoing boats, the number with which he began the war nineteen months earlier. Three of these boats were temporarily unavailable because of battle or other damage; three were patrolling off West Africa. That left only twenty-one boats to patrol the North Atlantic convoy routes, and half of these were new. Owing to the travel and refit time, only a third—seven boats—could be in the hunting grounds at one time. In view of the clever diversion of convoys and the ever-growing numbers of experienced, aggressive-minded surface escorts, there were simply not enough U-boats to find, track, and carry out successful pack attacks on enemy convoys in the Northwest Approaches.

The decision to disperse the U-boats to distant waters west of Iceland and to the South Atlantic entailed a severe penalty. The Type VIIBs and VIICs in the North Atlantic did not have sufficient fuel capacity for extended patrolling at long ranges, especially if required to chase one or more convoys at high speed. The fuel limitations were to reduce the number of boats available to form a pack in the more westerly North Atlantic hunting grounds. Similarly, the extreme distances involved in South Atlantic patrolling were to reduce the combat availability of the bigger boats sent to that area. Notwithstanding the prospective increase in the size of the Atlantic U-boat force, the number of boats that could be brought to bear on enemy shipping on any given day was to decline.

It was at this time—March 1941—that Lend-Lease was enacted and that President Roosevelt transferred the ten Coast Guard cutters to the Royal Navy (in addition to the fifty destroyers), and authorized other measures to provide the British cargo ships and tankers, to reinforce the British oil “shuttle” in American waters, and to repair British warships in American shipyards. Dönitz characterized these measures as “a chain of breaches of international law” and urged Hitler to lift the tight restrictions on attacking American ships. Absorbed with planning operations in the Soviet Union, the Balkans, and the Mediterranean Basin, Hitler was still wary of antagonizing the Americans and risking open warfare with them, and rejected the proposal.

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DECLINING U-BOAT PROSPECTS IN NORTH ATLANTIC - APRIL 1941

The U-boat war in the Atlantic proceeded in conformity to Dönitz’s decision to withdraw from the Northwest Approaches. On April 1 he shifted the nine boats in the hunting ground very far to the west. They formed a north-south patrol line at 30 west longitude—about equidistant between Iceland and Greenland—where Dönitz assumed British ASW measures to be less intense. At the same time, he ordered four big boats to sail to West African waters to reinforce the three boats already patrolling that area.

Dönitz had only just established the nine-boat patrol line to the southwest of Iceland on April 1 when U-76, a new VIIB outbound from Germany, discovered the fifty-one-ship convoy Outbound OB 305 in the Northwest Approaches area, 400 miles to the east! The U-76 was commanded by Friedrich von Hippel, age twenty-six, who had begun the war as a watch officer on Werner Hartmann’s U-37 but had been beached because of chronic stomach problems. The boat had been delayed in training by the Baltic ice and, after sailing from Kiel, had aborted to Bergen with mechanical difficulties. She had been in the Atlantic merely two days.

Because of the “strong” ASW measures in the Northwest Approaches, Dönitz was reluctant to bring the other boats back to the east. He therefore instructed von Hippel not to attack but to track the convoy 400 miles to westward, into the waiting arms of the patrol line, a challenging and risky assignment for a green skipper. The British were almost certain to DF von Hippel’s position reports, go after him, and divert the convoy. Von Hippel hung on, but during that day he ran into “sailing vessels and trawlers” south of Iceland and was forced to run submerged for nine hours to evade detection. When he surfaced to report losing the convoy, Dönitz directed him to “press on” to the west and to do his “utmost” to regain contact.

Meanwhile, one of the new boats in the western patrol line, Eitel-Friedrich Kentrat’s U-74, encountered inbound Slow Convoy SC 26, twenty-two ships escorted by the 11,400-ton auxiliary cruiser HMS Worcestershire. When Dönitz received this contact report, he instructed Kentrat to shadow and send beacon signals and not to attack until the other boats came up. Herbert Schultze in U-48, who had only one torpedo left and was low on fuel, could not respond, but the other eight boats did, forming the largest pack yet.

The pack commenced attacking late in the evening of April 2. Engelbert Endrass in U-46, who had previously sunk two ships for 10,500 tons, including the 8,700-ton Swedish tanker Castor, on this patrol, led the assault. He sank another tanker, the 7,000-ton British Reliance, and a 4,300-ton freighter, but a torpedo that hit the 4,900-ton British freighter Thirlby failed to detonate and another missed the 5,400-ton British freighter Athenic. Eitel-Friedrich Kentrat in U-74 attacked second, sinking a 5,400-ton Belgian freighter and a 4,300-ton Greek freighter and damaging the single escort, the auxiliary cruiser HMS Worcestershire. Helmut Rosenbaum in the new U-73 attacked third, sinking a 5,800-ton freighter and a 6,900-ton tanker, British Viscount, which exploded in flames, brilliantly lighting the seascape.

British Admiralty and RN Western Approaches Command in Liverpool were stunned to learn of U-boats attacking so far west. On orders of the convoy commander, the surviving sixteen ships scattered, some firing guns at real or imagined U-boats. Westwern Approaches Command, meanwhile, directed other escorts to the scene. A destroyer, HMS Hurricane, escorted the damaged auxiliary cruiser HMS Worcestershire on to Liverpool. Two destroyers, HMS Havelock and HMS Hesperus, searched for survivors of the six sunken ships. Five other warships, including the destroyers HMS Veteran and HMS Wolverine, rounded up the other scattered ships and reformed them into a convoy. By happenstance, the new boat, von Hippel’s U-76, which was still westbound in search of convoy Outbound 305, ran across the tracks of the scattered ships of Slow Convoy 26. At 0630 on the morning of April 3, von Hippel fired two torpedoes at one of the ships, the 2,000-ton Finnish freighter Daphne. Both missed, but von Hippel tracked submerged and five hours later he sank her.

The other U-boats pursued the reforming convoy eastward. That night, April 3–4, two of the boats caught up and attacked. Herbert Kuppisch in U-94 sank a 5,400-ton British freighter. Robert Gysae, age thirty, in the new VIIC U-98, on his maiden patrol, sank two other freighters. While the destroyer Veteran rescued survivors, the destroyer Wolverine counterattacked the U-boats, driving them off and holding them down, preventing preventing further attacks. Late in the afternoon of April 4, while running submerged, von Hippel in U-76 sighted another ship from the convoy, the 5,400-ton British freighter Athenic, sailing alone. Von Hippel attacked, firing one torpedo, which hit. The crew of Athenic radioed an alarm and then abandoned ship. Still submerged, von Hippel came in from the other side and fired two more torpedoes. Both hit; Athenic blew up with a thunderous roar. Upon hearing Athenic’s submarine alarm—SSS—four escorts that were shepherding the remnants of the convoy raced to the scene: the destroyers HMS Havelock and HMS Wolverine (credited with sinking Prien in U-47), the corvette HMS Arbutus (credited with sinking Matz in U-70), and the sloop HMS Scarborough. When they closed the area early on the morning of April 5, von Hippel in U-76 was on the surface, charging batteries. The watch saw one of the escorts and crash-dived. HMS Wolverine obtained sonar contact and notified HMS Arbutus and HMS Scarborough. Bedeviled by a sonar malfunction, HMS Wolverine dropped only two depth charges, one at a time. HMS Arbutus got sonar contact but lost it in the noise of HMS Wolverine’s attack. Coming up, the sloop HMS Scarborough gained a firm sonar contact and fired off eight depth charges.

The ten charges dropped on U-76 fell close. The first single charge from HMS Wolverine smashed all the instruments. The next caused a welded seam to give way, bent a stanchion, and put out all the lights. The eight charges from Scarborough caused severe flooding aft. Believing the boat to be doomed, at 0925, merely four minutes after HMS Scarborough’s attack, von Hippel surfaced to scuttle.

In compliance with the Admiralty’s standing orders, the corvette HMS Arbutus boldly ran in to try to capture a U-boat. While von Hippel and his crew were leaping into the water, Arbutus nuzzled alongside U-76. The first lieutenant of HMS Arbutus, Geoffrey Angus, and three seamen jumped on the forward deck of U-76—the first British in the war to board a German U-boat. While they raced to the bridge to enter the boat and grab the Enigma and secret papers, other hands from HMS Arbutus tied cables and an 8″ hawser to U-76 in an attempt to prevent her from sinking. When Angus reached the conning-tower hatch, he saw the boat was “half full” of seawater. The water had mixed with the battery acid, causing strong chlorine gas. Deciding it would be fatal to enter the boat, Angus slammed down and dogged shut the conning-tower hatch to stop the escape of air and to keep the boat afloat. It was a heroic try, but U-76 was still flooding aft and sinking rapidly. To save herself from capsizing, Arbutus had to let go the wires and hawser, and the boat sank. HMS Wolverine picked up von Hippel and thirty-nine of his crew; HMS Scarborough andHMS Arbutus rescued one man each, for a total of forty-two. The British noted that a seaman on U-76 died when saltwater leaked into the potash cartridge of his escape apparatus, producing a toxic gas that he inhaled.

Counting the survivors of U-70, U-76, U-99, and U-100 captured during March 1941, Royal Navy had captured 113 German submariners (fourteen officers, ninety-nine enlisted men) within one month. Some of these POWs talked freely (or were coerced or tricked into talking freely) and revealed many technical details about the Type VII boats, the organization of the U-boat arm, and the French bases. One of the officers even told the British about the rift that had occurred between Dönitz and Göring over command of the Condors. According to a British intelligence report, another German officer revealed the “astonishing” successes B-dienst had achieved in breaking British naval codes, but that was old stuff.

When Dönitz queried the boats for sinking reports on Slow Convoy 26, he calculated the pack attack had been highly successful: twelve (of twenty-two) ships sunk for 80,000 tons, plus damage to the auxiliary cruiser Worcestershire. He was close. Unknown to Dönitz, the lost U-76 had sunk two ships of the convoy for 7,400 tons, which brought the confirmed total to eleven ships sunk (of twenty-two) for 54,000 tons.

The retreat from the dangerous Northwest Approaches to more distant waters westward appeared to be not a defeat but a stroke of genius in the case of Slow Convoy 26. For the loss of only one (green) boat, U-76, the pack had sunk eleven confirmed ships inbound to the British Isles with full and valuable loads. But the discovery of and success against that convoy was really beginner’s luck. The big expenditure of fuel to get to westward of Iceland severely restricted the ability of the VIIs to hunt and chase the enemy.

The loss of eleven ships (two tankers) in Slow Convoy 26 so far to the west of Iceland speeded up a plan to base substantial British ASW forces in Iceland to extend strong convoy protection farther to the west of that island. This decision, in effect, filled a gap caused by the postponement of the U.S. Navy plan to provide convoy escort on the Iceland-Canada leg and the delays in readiness of the Canadian corvettes. British Admiralty sent three of the newly formed Escort Groups to Iceland: B-3, B-6, and B-12. These groups were, so to speak, spliced into the center of the North Atlantic convoy run. They were to meet the escorts of westbound convoys at about 20 degrees west and relieve them. Then they were to escort those convoys to about 35 degrees west (900 miles or about five days), whereupon they were to turn about and escort eastbound convoys (Slow, Halifax) back to about 20 degrees west, where they were to hand over convoy protection to those escorts returning to the British Isles. Inasmuch as these escorts had limited range, especially in heavy weather, and had to run into Iceland to refuel, three groups were required to carry out this scheme. In addition, the Admiralty transferred Coastal Command Sunderlands and Hudsons to Iceland. These planes, equipped with 1.5-meter-wavelength ASV II radar sets, were to provide air protection for the convoys. Although ground facilities were as yet primitive, the aircrews were able to take advantage of the improved April flying weather and the longer days (and shorter nights), which increased opportunities to sight by eye surfaced U-boats.

It should not be imagined that the British suddenly put in place a strong and reliable splice in the North Atlantic convoy run. The new system required terribly rigid convoy routing and escort scheduling. Working on an overly intricate timetable unforgiving of error, the surface and air escort, manned by green crews, often became lost and were unable to find the convoys, throwing everything into confusion. Ships and planes broke down or ran short of fuel and had to abort missions. Inclement weather and the presence of icebergs complicated the linkups. Moreover, the extreme rigidity of the scheme raised the possibility that the Germans might divine the convoy routes and rendezvous and take advantage of the weak links in the splice.

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Dönitz had laid plans for a major U-boat campaign in West African waters during April, employing seven large boats, which were to replenish, as required, from the German supply ships Nordmark and Egerland, parked in mid-Atlantic. During last two weeks of April 1941 , U-105 and U-124 sunk seven more single sailing merchant ships off West Africa. Dönitz preferred replenishing the boats from German supply ships in the South Atlantic , sent U-103 and U-107 in their place after their patrol ended.

In mid-April there were nine U-boats in the North Atlantic hunting grounds. Six patrolled a line well southwest of Iceland. Two patrolled directly south of Iceland. A new VIIB, U-75, commanded by Helmuth Ringelmann, age twenty-nine, was westbound through the Northwest Approaches.
Three of the eight boats were low on fuel and poised to return to France; three others, including a new VIIC, U-553, commanded by Karl Thurmann, age thirty-one, sailed to replace them. However, U-553 was compelled to abort to Bergen with engine problems.

The hunting in these distant western waters was disastrously poor. In the three-week period April 4 to April 25, the boats attacked no convoys. In the two-week period April 10 to April 25, only three boats had successes: Otto Salmann in U-52 (two ships for 14,000 tons), Helmut Rosenbaum in U-73 (one ship for 8,600 tons), and Karl-Heinz Moehle in U-123 (one ship for 7,300 tons).

One of the ships sunk by Salmann in U-52 was the 6,600-ton Dutch freighter Saleir, an empty straggler from convoy Outbound OB 306 convoy. She went down on April 10 near 31 degrees west. As it happened, a new (1940) American destroyer of the Argentia-based American Support Force, USS Niblack, commanded by Edward R. Durgin, was close by on a reconnaissance patrol. Durgin rescued three boatloads of survivors and while doing so, his sonar operator reported contact on a U-boat. Durgin went to battle stations and drove off the U-boat with three depth charges. According to USS Niblack’s official history, “This bloodless battle apparently was the first action between American and German forces in World War II.”

The complete absence of convoy contacts aroused suspicion in Kerneval. Dönitz became convinced three must be a spy in the German or Italian armed forces giving away U-boat positions. He imposed drastic new restrictions on the number of people at Kerneval, Bordeaux, Berlin, and elsewhere who were authorized to know the position of U-boats, or to tune in on U-boat radio traffic. At his request, Admiral Raeder sent the following tough message to all Kriegsmarine commands: The U-boat campaign makes it necessary to restrict severely the reading of signals by unauthorized persons. Once again I forbid all authorities who have not express orders from the operations division or the admiral commanding U-boats to tune in on the operational U-boat [radio] wave. I shall in the future consider all transgressions of this order as a criminal act endangering national security. It also occurred to Dönitz that the British had possibly improved DFing and—inconceivable as it seemed—broken the naval Enigma. He therefore ordered the boats to maintain strict radio silence, except when reporting weather or convoy contacts, and requested the OKM to introduce “a new U-boat cipher.” The OKM, Dönitz logged, “approved” his request for a new cipher, but putting it into service was to take a very long time. (like ten months or so !)

Dönitz was correct on both counts. The British Admiralty had improved DFing and, no less important, the processing of DF information. Moreover, commencing April 22, the codebreakers at Bletchley Park, utilizing the material captured from German trawler the Krebs in the Norway raid (Operation Claymore , first large scale British Commando raid oN Lofoten islands at Norway on 3rd March 1941 , German trawler and its Enigma material was captured there) and “cryptanalytical methods,” broke “the whole of the [Enigma] traffic of April 1941,” the official historian wrote. Hence Rodger Winn in the U-boat Tracking Room of the O.I.C. was privy to all U-boat traffic for the months of February (previously broken) and April. That traffic, plus traffic from the hand cipher Werft, provided him with a complete picture of U-boat operations for those two months, including Dönitz’s decision to shift the boats out of the Northwest Approaches to the waters west of Iceland.

From the February and April Enigma traffic, Bletchley Park learned for the first time that the Kriegsmarine maintained a fleet of eight trawlers in the Atlantic for weather reporting. At least two of the trawlers were at sea at any given time, one north of Iceland, one in mid-Atlantic. The trawlers carried naval Enigma. They broadcast weather reports in a special cipher, Wetterkruzschlüssel, and also carried “short signal” books. A naval officer at Bletchley Park, Harry Hinsley (later the distinguished historian of British intelligence), suggested that the Admiralty attempt to capture one of these trawlers at the earliest possible date to gain more Enigma keys and material. British Admiralty looked upon this suggestion favorably and commenced drawing plans. This proposed capture “at sea” was not out of the ordinary. Over a year prior, the commander of the Home Fleet, Charles Forbes, had urged all light Royal Navy vessels to form a “boarding party” for the purpose of capturing a U-boat.

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Frustrated by the lack of successes on the North Atlantic run and believing that he might have overreacted to the British ASW threat, in the waning days of April , Dönitz shifted the bulk of the North Atlantic U-boat force eastward toward the British Isles. Late on the afternoon of April 27, Erich Topp in U-552 found a big target at about 17 degrees west longitude: the 10,100-ton British freighter Beacon Grange, sailing alone. Topp attacked submerged, firing all four bow tubes. The ship went down; the crew broadcast the submarine alarm, SSS, then took to the lifeboats.

Nine hours later, April 28, Karl-Heinz Moehle in U-123 found convoy (Halifax) HX 121 at about 17 degrees west. It was composed of forty-seven ships and was guarded by nine escorts. The convoy offered the Germans in that area the first opportunity in almost four weeks to mount another pack attack. Dönitz instructed Moehle to shadow and broadcast beacons, so the other boats in the area and Condors from France and Norway could converge.

The British DFed Moehle’s shadow reports and warned the convoy commander as well as the commander of convoy Outbound 314, which was passing close by on a westerly course. The warning helped some. The escorts attempted to drive Moehle off for good, but he hung on tenaciously, regaining contact at dawn. The Condors failed to locate the convoy and the escorts forced Moehle off again and he lost contact, but three other boats made contact with it later in the day.

The convoy commodore was fully aware that U-boats were converging, but he did not expect an attack before dark. Erich Topp in U-552, who had submerged ahead of the convoy, did not wait. In mid-afternoon, he let the lead escorts pass, then fired at the 8,200-ton British tanker Capulet. Some torpedoes hit, wrecking the ship, but it did not sink. Admiralty intelligence noted later that this was the first daylight attack by a submerged U-boat on a fully escorted convoy since the summer of 1940. Later, some ASW experts speculated that in view of the strengthened convoy escort and the coming of short nights, all the U-boats in the northern area might revert to strictly daylight submerged attacks. The escorts counterattacked. Two destroyers, HMS Maori and HMS Inglefield, found U-552 on sonar and delivered five depth-charge attacks. These held Topp down for hours while the convoy proceeded and, as a result, Topp was unable to mount a second attack. Meanwhile, three escorts from convoy Outbound 314 joined convoy Halifax HX 121, raising the total escorts to twelve. One of the joining escorts, the destroyer HMS Douglas, attempted to sink the wrecked tanker Capulet by gunfire, but failed, then joined in the U-boat hunt.

After dark Lehmann-Willenbrock in U-96 broadcast another position report, then attacked on the surface. In a well-aimed salvo of four bow torpedoes, he sank three big loaded ships: the 8,500-ton British tanker Oilfield, the 9,900-ton Norwegian tanker Caledonia, and the 8,900-ton British freighter Port Hardy. The Oilfield burst into flames which lit up the scene and forced Lehmann-Willenbrock to dive, losing an opportunity for a second attack. All three ships, totaling 27,300 tons, sank.

The twelve escorts hunted relentlessly. The corvette HMS Gladiolus got a sonar contact and dropped ten depth charges. Joined by two ex-American four-stack destroyers from convoy Outbound OB 314, Leamington and Roxborough, the three ships carried out four further depth-charge attacks. The other newly arrived escort, the British destroyer Douglas, delivered a punishing depth-charge attack on what proved to be IXB class submarine U-65, under a new skipper, Joachim Hoppe, age twenty-six, who had commanded the boat merely sixteen days and had not yet fired any torpedoes. The attack destroyed U-65. There were no survivors. She was the seventh U-boat lost in the waters of the Northwest Approaches in as many weeks.

Dönitz made every conceivable effort to mount continuing attacks on Halifax HX 121 by U-boat and Condor, but Royal Navy Western Approaches Command cleverly routed the convoy away from the boats and all efforts to find it again failed. In total, four boats had made contact. Two boats had shot torpedoes which had resulted in the sinking or destruction of four ships, three of them loaded tankers. That was a blow, but the other forty-three ships of convoy HX 121 reached port safely.

During April, 307 loaded ships sailed in convoys from Halifax to the British Isles. German U-boats sank sixteen vessels (five tankers) from these convoys—eleven from SC 26, four from convoy HC 121, and a small straggler from HX 117. Besides that, the oceangoing U-boats sank eleven other ships (one tanker) for about 70,000 tons, which were sailing alone per the new policy that allowed ships of 12 knots or faster to go it alone. Total sinkings by U-boats in the North Atlantic area in April therefore came to twenty-seven. In return, two U-boats, U-65 and U-76, had been lost. As before, the very great successes of the U-boats in the waters off West Africa tended to obscure pathetic convoy hunting on the North Atlantic run.