The end of the U-boat aces

At about 3.18 a.m. on 17 March 1941, in the North Atlantic south-east of Iceland, the British destroyer HMS Vanoc drove her bows into the hull of the German submarine U-100, which had surfaced a few minutes earlier after being damaged by depth charges. Her commander, Kapitänleutnant Joachim Schepke, one of the three most celebrated aces of the German submarine arm, was killed on the bridge. Less than half an hour later, at 3.43 a.m., the crew of U-99, depth-charged by the destroyer HMS Walker, scuttled their boat and took to the water. Her commander, Otto Kretschmer, the most successful U-boat commander of the war, was taken prisoner by the British. Ten days earlier, on the night of 7–8 March, Günther Prien’s U-47, the boat that had penetrated Scapa Flow, had vanished without trace.

Under 17 March chronologies carry a general note about “enormous convoy losses in the mid-Atlantic this week”. That does not quite capture the meaning of these days. The losses were serious but not exceptional: convoy HX 112, the subject of the battle of 16–17 March, lost five ships, and over the whole of March the U-boats sank roughly as much as in February. What was exceptional was something else. Within ten days Karl Dönitz lost his three best commanders and five boats, and for the first time in the war a British escort clearly won an encounter with a wolf pack.

The height of the “happy time”

From the summer of 1940 German submarines operating from bases in France had been achieving their greatest successes in the Atlantic since the start of the war. Their crews called this period “the happy time” (die glückliche Zeit). A small number of boats, attacking at night on the surface, where the British ASDIC could not detect them, tore apart weakly protected convoys: HX 72 in September 1940, SC 7 and HX 79 in October. The most famous commanders – Prien in U-47, Kretschmer in U-99 and Schepke in U-100 – became heroes of German propaganda. After a winter lull caused by storms and the small number of boats, success returned in February 1941: at the end of the month U-boats and Focke-Wulf Fw 200 Condor aircraft shattered convoys OB 288 and OB 290 without losing a single boat.

On the British side, however, changes were under way that were beginning to bear fruit. In February 1941 Western Approaches Command, responsible for protecting shipping in the approaches to the British Isles, moved to Liverpool, and its new commander, Admiral Sir Percy Noble, built up permanent escort groups whose ships sailed and trained together under a single commander. New Flower-class corvettes and former American destroyers were joining the escorts, and the first, still primitive, radar sets were being fitted in some ships. On 6 March Winston Churchill issued a directive proclaiming “the Battle of the Atlantic” and giving it the highest priority, and on 19 March the Cabinet committee he had set up to conduct it met for the first time. Earlier, on 11 March, President Franklin Delano Roosevelt had signed the Lend-Lease Act, but American aid made sense only if the ships from America reached British ports.

OB 293: the disappearance of Prien

Convoy OB 293, 37 ships sailing in ballast or with general cargo for North America, left Liverpool on 2 March 1941. It was escorted by two old destroyers, HMS Wolverine and HMS Verity, and two corvettes, Arbutus and Camellia, under the command of Lieutenant Commander J. M. Rowland in Wolverine. On 6 March, south of Iceland, the convoy was sighted by Prien, who had sailed from Lorient on 20 February on his tenth patrol. Prien sent a sighting report and shadowed the ships, and in the course of the day three more boats joined him: Kretschmer’s U-99, the new U-70 under Kapitänleutnant Joachim Matz, on her first patrol, and Hans Eckermann’s large boat UA.

The attack began on the night of 6–7 March. Kretschmer penetrated the formation from ahead and sank the tanker Athelbeach, already damaged by U-70, and torpedoed the huge whale factory ship Terje Viken, of more than 20,000 GRT, which Prien also hit. The damaged ship stayed afloat for another week before sinking while an attempt was made to tow her into port. Matz damaged two tankers, the British Delilian and the Dutch Mijdrecht; the Dutch master steered his ship straight at the submarine to ram it and forced it to dive. This time the escort reacted quickly and effectively. For about five hours the ships dropped more than a hundred depth charges. U-99 escaped by going deep, UA was damaged, and U-70, forced to the surface, sank under fire from the corvettes Camellia and Arbutus. Twenty men were killed and 25, among them Matz, were taken prisoner.

Prien stayed with the convoy and was still sending reports on the morning of 7 March. He sent his last at 4.54 a.m. After that U-47 was never heard from again. For half a century it was accepted that on the night of 7–8 March she had been sunk by Wolverine, which after a pursuit lasting several hours depth-charged a submarine and saw an underwater explosion with an orange glow. Research in the 1990s, based on German and British documents, showed, however, that Wolverine had then been attacking UA, which despite heavy damage returned to base. The fate of U-47 and her crew of 45 remains unexplained: she may have struck a mine, suffered a diving accident or been sunk by one of her own torpedoes running in a circle. Convoy OB 293 lost three ships – the third, Dunaff Head, was sunk by UA on 8 March – and two more were damaged. The Germans lost two boats, and a third returned to base heavily damaged.

HX 112: the night of 16–17 March

Convoy HX 112, 41 ships, many of them tankers carrying fuel for Britain, left Halifax (PL) on 1 March. It was escorted across the ocean by the armed merchant cruiser HMS Ranpura, and in the approaches to the British Isles it was taken over by the 5th Escort Group, reinforced because of the valuable cargo. The group comprised the destroyers Walker, Vanoc, Sardonyx and Scimitar and corvettes, including Bluebell. It was commanded by Commander Donald Macintyre in Walker, an experienced officer who had recently taken over the group; the defence of HX 112 was his first great battle in that role.

On 15 March the convoy was sighted by U-110 under Kapitänleutnant Fritz-Julius Lemp, the same man who in September 1939 had sunk the Athenia. Lemp sent a report and shadowed the ships, and during the day Dönitz directed four more boats onto the convoy: Kretschmer’s U-99, Schepke’s U-100, U-37 and U-74. On the night of 15–16 March Lemp torpedoed the tanker Erodona, which caught fire but managed to reach port. Other attacks that night were frustrated by the escort, which began depth-charging every contact detected and forced the boats to dive, causing them to lose the convoy.

On the evening of 16 March the boats, which had spent the day on the surface near the convoy, tried again. Kretschmer did what he had done many times before: at about 10 p.m. he slipped on the surface into the middle of the formation from the port wing and fired at ship after ship at close range. In about an hour he sank three tankers, the Norwegian Ferm and Beduin and the British Venetia, as well as the Canadian freighter J. B. White and the Swedish Korshamn, and damaged the tanker Franche-Comté, which later reached port. He had fired all his torpedoes and began to withdraw on the surface, away from the convoy. The escorts, searching for submarines outside the formation, did not spot him. Walker turned back to rescue survivors and picked up 38 men from J. B. White.

Schepke’s death and Kretschmer’s capture

Shortly after midnight the escort came upon U-100, which was trying to approach the convoy. According to British accounts, at about 1.30 a.m. Walker and Vanoc detected her as she dived and depth-charged her. Schepke’s boat, leaking and damaged, survived the attack, and shortly before 3 a.m. he decided to surface, hoping to escape in the darkness on the surface. Vanoc had recently been fitted with a simple Type 286 radar set, designed to detect surface targets. Its operator detected the surfaced boat at a range of about a kilometre, although it could not be seen from the bridge. This was the first time in the war that a British surface ship had detected a U-boat by radar and then destroyed it. Vanoc’s commander, Lieutenant Commander James Deneys, went in at full speed and at 3.18 a.m. rammed U-100 near the conning tower. Schepke was standing on the bridge and, according to survivors, was crushed between the conning tower and the destroyer’s bows. The boat sank within minutes. Of the 44 men on board, six survived according to the tallies of the uboat.net service; other studies give slightly different figures.

While Vanoc and Walker were picking up survivors from U-100, Kretschmer’s boat, slipping away on the surface, ran into one of the destroyers in the dark. According to the crew’s account, the officer of the watch, contrary to his commander’s standing order to escape on the surface in such a situation, ordered the boat to dive. Under water U-99 was at once picked up by Walker’s ASDIC. After a pattern of depth charges the damaged boat began to sink deeper, beyond her safe depth, and Kretschmer could save her only by an emergency surfacing. On the surface she came under fire from the guns of both destroyers. He then ordered the boat to be scuttled and asked Walker by signal lamp to rescue his crew. At 3.43 a.m. U-99 went to the bottom. Three men were killed, among them the boat’s engineer, who had gone below to open the valves. Forty, Kretschmer among them, were picked up by Walker. Macintyre kept Kretschmer’s binoculars as a souvenir and used them until the end of the war; he returned them to his former adversary in 1955.

That was the end of the battle. The remaining boats lost contact, and convoy HX 112 reached Liverpool on 20 March. It had lost five ships totalling some 34,500 GRT, and two more had been damaged. The Germans had lost two of their best boats and their two most famous commanders.

March on both sides

The battles around OB 293 and HX 112 were not the only events of March in the Atlantic. On 23 March, south of Iceland, the British armed trawler Visenda sank U-551, on her first patrol, with all hands. Within a single month, therefore, the Germans lost five submarines, whereas in February they had lost none in the Atlantic. With only twenty-odd front-line boats this was a painful loss, and more painful still was the loss of experienced commanders and crews, who could not be quickly replaced. Prien, Kretschmer and Schepke had between them sunk more than a hundred ships, most of them in just nine months, when British defences were at their weakest.

The number of ships sunk, however, did not fall at all. According to the tallies of uboat.net, in March 1941 U-boats sank some 40 ships totalling about 235,000 GRT, slightly more than in February. A large part of these successes went to boats operating far from the British Isles. The large Type IX boats U-105, U-106 and U-124 attacked convoys SL 67 and SL 68 from Freetown in West African waters, and on 20 March U-106 even torpedoed the escorting battleship HMS Malaya, which reached port. During these weeks the German battleships Scharnhorst and Gneisenau were also at large in the Atlantic; on 15 and 16 March they destroyed dispersed ships from westbound convoys, and on 22 March they put into Brest. Altogether, counting the victims of surface ships, aircraft and mines, March 1941 was one of the worst months for British shipping in this period of the war.

Dönitz did not know at once what had happened. The boats simply stopped answering the calls from headquarters. Confirmation of Kretschmer’s and Schepke’s fate came from the British side, which quickly announced that it had captured the most successful U-boat commander. The German Wehrmacht report confirmed Schepke’s death only on 25 April, and announced Prien’s loss on 24 May, hiding the news among reports of successes. At U-boat headquarters there was speculation as to whether the British had a new device for detecting boats on the surface, but the question could not be settled. Dönitz concluded that in the approaches to the British Isles, where the escorts were strongest and the aircraft of RAF Coastal Command ever more numerous, attacks had become too costly. He moved his patrol lines further west, into the mid-Atlantic, beyond the reach of the British escorts, and sent more and more boats to distant hunting grounds off the coast of Africa.

British lessons

For the Royal Navy the defence of HX 112 was proof that the changes introduced since the autumn of 1940 were working. The conclusions that Macintyre later set out in his memoirs were simple: the escort should not scatter in pursuit of individual contacts but stay with the convoy, because that is where the submarines must eventually show themselves; and the ships of a group must know each other and act according to common, simple rules. The night of 16–17 March also showed the importance of new equipment. ASDIC, which could not see a boat on the surface, was now supported by radar – still unreliable and fitted in only a few ships, but improving month by month. A few weeks later, in May, escort ships captured cipher material and an Enigma machine from Lemp’s U-110, which, together with the material seized in early March during the Lofoten raid, helped the codebreakers at Bletchley Park to read the signals of the German U-boat arm.

This victory should not, however, be overrated. British escorts were still few in number, and most ships had no radar. Outbound convoys were still dispersed west of Ireland, and in the mid-Atlantic, where Dönitz had moved his boats, ships sailed without protection. Only in the following months, from bases in Iceland and from June 1941 also from Newfoundland, did escorts begin to accompany convoys across the whole ocean.

Place in the war

March 1941 closed the first phase of the Battle of the Atlantic, which the German crews called “the happy time”. Historians date its end differently – some as early as October 1940, others March or April 1941 – but the loss of Prien, Schepke and Kretschmer within ten days became its symbolic close. From then on U-boats could no longer attack well-escorted convoys with impunity on the surface from inside the formation, and the tactics on which the most famous aces had built their success were becoming ever more dangerous to themselves.

For Germany it was also a propaganda loss. The three commanders had been heroes of newsreels, books and meetings with young people; the regime concealed their fate for many weeks and then presented them as models of self-sacrifice. For the British, who in those same weeks were enduring further heavy raids on their cities and ports, it was the first clear success in the war against the U-boats.

The Battle of the Atlantic, however, went on until the end of the war in Europe, and its hardest years still lay ahead for both sides. The German U-boat arm grew rapidly: from twenty-odd front-line boats at the beginning of 1941 to more than a hundred the following year. After the United States entered the war in December 1941, the U-boats enjoyed a “second happy time” off the American coast, and in the winter of 1942–1943 they were sinking more ships than ever before. The turning point came only in May 1943, when radar, long-range aircraft, escort carriers and the reading of German ciphers reversed the balance of the struggle. March 1941 showed for the first time that the wolf packs could be beaten – but the road to that victory was still a very long one.