HITLERS WOLFPACKS
How Germany’s U-boat tactics crippled Allied shipping but failed to win the Battle of the Atlantic
Following the Allied victory in 1945, British Prime Minister Winston Churchill admitted in his multivolume history of the conflict that “the only thing that ever really frightened me was the U-boat peril.” Through the lens of history it is easy to understand his concern as the Battle of the Atlantic unfolded and the island nation fought for its life against marauding German U-boats that relentlessly attacked Allied merchant shipping. From the day that Britain declared war on Nazi Germany through to 1945, the submarines of the German navy, the Kriegsmarine, under the capable but sometimes questionable command of Admiral Karl Dönitz, sank approximately 3,500 merchant vessels and 175 warships, sending 14 million tons of vital shipping to the bottom of the sea.
The U-boats’ heavy toll on Allied merchant shipping was punctuated by remarkable successes against Royal Navy warships, providing a surge of propaganda for the Nazis. Even so, of the 1,162 U-boats that were constructed during World War II 785 were lost. Service with the Ubootwaffe, the submarine arm, was fraught with peril. By the time the war ended an estimated 32,000 German sailors, 30 per cent of those who served aboard U-boats, had been killed – the highest percentage of casualties among German combat forces during the conflict.
An early angst
Despite advice from Admiral Dönitz and his direct superior, Grand Admiral Erich Raeder, that the Kriegsmarine would not be ready to go to war until 1944, Adolf Hitler launched the invasion of Poland on 1 September 1939, plunging the navy into a conflict for which it was ill-prepared. At the time Dönitz had only 56 operational U-boats – eight of which were only suitable for coastal operations or training. In the run-up to war he had pleaded for a building programme that would yield 1,000 ocean-going submarines with which to strangle the British Isles, but production was slow to gather pace.
Dönitz was a U-boat veteran of World War I and had commanded his own boat and been taken prisoner, so he understood the rigors of U-boat service. Blockade had been unsuccessful during 1914-18 due to Allied employment of the convoy system, a lack of efficient radio communications and mounting losses among the submarines during four years of attrition, but Dönitz recognised that a blockade might actually succeed if emphasis were placed on the construction and deployment of undersea raiders this time around. However, convincing senior Nazi military planners, including Hitler, that such a tactic offered the best chance for victory was a frustrating exercise for Dönitz, who struggled throughout the war to maintain a force sufficient to threaten Britain.
Law and orders
At the outbreak of war Dönitz had already deployed 22 U-boats to critical shipping lanes in the Atlantic. Such a small number of boats would never be sufficient to mount an effective blockade, but they did make their presence felt. The submarines reached the hunting zones around Britain by sailing around the northern tip of Scotland rather than through the treacherous passage of the English Channel. U-boat commanders initially received specific orders to abide by international maritime law.
They were to surface and stop
“OF THE 1,162 U-BOATS THAT WERE CONSTRUCTED DURING WORLD WAR II 785 WERE LOST. SERVICE WITH THE UBOOTWAFFE, THE SUBMARINE ARM, WAS FRAUGHT WITH PERIL”
merchantmen, identify the cargo, allow the crew to abandon ship and provide assistance prior to seizing or sinking their quarry. The German declaration of unrestricted submarine warfare had contributed to the entry of the United States into World War I, and Germany wanted to avoid such a situation as long as possible this time.
On 3 September 1939 the U-30, commanded by Kapitanleutnant Fritz-julius Lemp, sank the British passenger liner Athenia. Echoes of the Lusitania attack brought additional restrictions on U-boats, but as the war in the Atlantic gained momentum Dönitz became increasingly aware that surfaced U-boats exposed themselves to the fire of armed merchant ships and Royal Navy warships, as well as attack from enemy aircraft. Additionally, radio operators aboard some merchant vessels immediately transmitted the signal ‘SSS’, which meant that the ship was under attack by a U-boat. In the admiral’s mind this voided the rule of maritime law since the German submarine was then put at high risk.
The most frustrating aspect of the early U-boat combat experience was that their numbers were too few to fully implement Dönitz’s preferred offensive system, ‘Rudeltaktik’, or the ‘wolfpack’. With enough U-boats available, he had envisioned up to 15 submarines grouping to attack an Allied convoy, stretching any escorting warships to breaking point and inflicting maximum damage. A wolfpack was to patrol a particular zone of the vast Atlantic, covering a portion of an established convoy route. Once a submarine discovered a convoy, it would shadow the merchant ships and raise a radio advisory to headquarters, Befehlshaber der Unterseeboote (BDU), which
“DESPITE THE INABILITY TO RAPIDLY INTRODUCE WOLFPACK TACTICS ON A BROAD SCALE, EARLY U-BOAT SUCCESSES SHOOK THE ROYAL NAVY”
would in turn alert other boats in the area. When enough attackers were assembled to exploit the opportunity, headquarters would give permission to attack. Each U-boat could then act independently. Wolfpacks preferably struck at night and on the surface, launching torpedoes from distances of approximately 600 metres or in the midst of the ships at pointblank range, adhering to the Dönitz dictum,
“Get in as close as possible”.
Despite the inability to rapidly introduce wolfpack tactics on a broad scale, early
U-boat successes shook the Royal Navy. On 17 September 1939 U-29, commanded by Korvettenkapitan Otto Schuhart, sank the aircraft carrier HMS Courageous off the coast of Ireland. A month later Kapitanleutnant Günther Prien executed the most daring submarine manoeuvre of the war. On the night of 14 October he guided U-47 through the block ships and cables supposedly safeguarding the expansive anchorage of the Home Fleet at Scapa Flow in the Orkney Islands, sank the battleship HMS Royal Oak moored in the harbour and escaped into the North Sea.
Prien was summoned to Berlin for a personal audience with Hitler, awarded the Knight’s
Cross and became a national hero.
The game changes
Meanwhile, Dönitz was anxious to employ his wolfpack tactics on a grand
scale. Although the first co-ordinated U-boat attacks against British convoys were conducted as early as 1939, numbers were inadequate. He had outlined his plan for the wolfpacks to decimate enemy shipping in a memorandum to Admiral Raeder and noted that 300 operational U-boats would be needed to carry it out, given the fact that some would be active while others were either in transit or undergoing repairs.
Dönitz’s critics point to his fixation on the tonnage of merchant shipping sunk, and the necessity that German submarine production would be sufficient to augment his forces while Allied shipping construction failed to keep pace with losses inflicted by the U-boats. Neither premise materialised. Dönitz also lacked the vision to implement better technology earlier in the war. His Type VII U-boats had limited range, reducing their effectiveness across thousands of miles of ocean. Construction of longer-range Type IX and Type XXI boats came too late.
Early U-boat production actually crept upwards: only 18 had been completed in 1939, followed by 50 in 1940 and 199 in 1941. Along with these growing numbers, German successes on the battlefield yielded a tremendous advantage. The conquest of Norway and France in the spring of 1940 brought new bases with ready access to the Atlantic – in some cases 725 kilometres
(450 miles) closer to the shipping lanes than bases in the Baltic and North Sea. Soon, the French ports of Bordeaux, Lorient, St. Nazaire, La Rochelle and Brest were beehives of construction. Concrete submarine pens were built to shelter the U-boats. Wolfpack tactics were further developed and refined with the benefit of wartime experience.
While its performance in the Norwegian Campaign had been disappointing and its few successes had cost the U-boat arm four precious submarines, Dönitz re-energised
“THE MOST PROLIFIC U-BOAT COMMANDERS BEGAN TO RACK UP IMPRESSIVE RECORDS. KAPITANLEUTNANT OTTO KRETSCHMER, THE HIGHESTSCORING U-BOAT ACE OF THE WAR, COMMANDED U-23 AND U-99 AND ACCOUNTED FOR 47 SHIPS AND 273,043 TONS”
his command. In 1940 resurgent marauders sank 30 merchant ships, totalling more than 284,000 tons in June. During the so-called ‘Happy Time’ – six months of unprecedented successes that followed – U-boats sank 282 ships and 1,489,795 tons of cargo. Despite the successes, that autumn the Ubootwaffe remained capable of deploying only seven or eight submarines at a time.
Information from B-dienst, German naval intelligence, helped to locate convoys, and intrepid U-boat commanders scored remarkable successes. During a 30-hour killing spree in late October, two wolfpacks of only ten U-boats decimated Convoys SC 7 and HX 79, sinking 29 ships without loss.
The most prolific U-boat commanders began to rack up impressive records. Kapitanleutnant Otto Kretschmer, the highest-scoring U-boat ace of the war, commanded U-23 and U-99, and accounted for 47 ships and 273,043 tons. He was taken prisoner when U-99 was sunk on 17 March 1941 during a wolfpack attack on Convoy HX 112, eastbound from Halifax in Nova Scotia to Liverpool. Kapitanleutnant Wolfgang Lüth commanded multiple boats, including
U-43 and U-181, and ended the war with 46 ships and 225,204 tons sunk. Fregattenkapitan Erich Topp sank 35 ships and 197,460 tons while commanding U-57 and U-552.
Kapitanleutnant Joachim Schepke emerged as a hero during the Happy Time, sinking five ships in only three hours during one attack. Handsome and gregarious, Schepke gained fame commanding U-100 and lost his life in action on 17 March 1941 during the same wolfpack assault that resulted in Kretschmer’s capture. On 15 March Fritz-julius Lemp, commander of U-110, spotted HX 112 and sent a signal for the grey wolves to rally. Four U-boats – U-99, U-100, U-37, and U-74 – responded. After dark, Schepke manoeuvred
U-100 within range of a large tanker and damaged it with a torpedo. Kretschmer, meanwhile, sank four tankers and a freighter in less than an hour. He followed that up with the sinking of another freighter within 15 minutes as he stalked the central column of the convoy and then made good his temporary escape.
But Schepke’s luck was running out. The 41-ship convoy was escorted by six destroyers and corvettes, and they prowled the night, catching U-100 on the surface. At around 1.30am Schepke ordered his crew to crash dive. However, the destroyer HMS Walker was hot on the trail and laid a pattern of depth charges at close range. Schepke’s boat shook and shuddered, sustaining damage. About 90 minutes later he brought the stricken U-100 back to the surface, only to see the destroyer HMS Vanoc bearing down, ready to ram.
Vanoc, first to use shipboard radar at night to locate an enemy submarine, sliced into the hull of U-100, dealing a deathblow and crushing Schepke against his periscope as the submarine sank. 37 other crewmen died with U-100; only six survivors were picked up. Kretschmer and U-99 fell victim to Walker, which picked up the submarine on ASDIC, an underwater sound detection system developed during World War I, and damaged the U-boat with depth charges, forcing it to surface.
Other escorts riddled U-99 with gunfire. As the submarine sank, Kretschmer and most of his crew were scooped from the sea.
After losing six ships and 50,000 tons of cargo, Convoy HX 112 continued without further incident, arriving at Liverpool on 20 March. The loss of two U-boat aces was a serious blow to the Kriegsmarine, compounding the melancholy accompanying the death of Günther Prien, hero of Scapa Flow, during an attack on Convoy OB 293 en route from Liverpool to North America. On the night of 6 March a wolfpack of four U-boats – U-47, U-99, U-70 and U-A (formerly a Turkish submarine built in Germany) – moved against convoy OB 293 in the Western Approaches in the Atlantic.
Prien made the rallying call, stalked the convoy and attacked after dark. The wolfpack sank four ships and damaged a fifth. However, the response from the escorts was devastating. The corvette HMS Camellia sank U-70 on 7 March, while the destroyer HMS Wolverine has been credited with depth charging U-47 and killing Prien. Some researchers conclude that Wolverine attacked U-A, which limped back to port, but the actual cause of U-47’s demise is shrouded in conjecture and possibly attributable to damage followed by a diving accident.
“PRIEN MADE THE RALLYING CALL, STALKED THE CONVOY AND ATTACKED AFTER DARK. THE WOLFPACK SANK FOUR SHIPS AND DAMAGED A FIFTH. HOWEVER, THE RESPONSE FROM THE ESCORTS WAS DEVASTATING”
Countermeasures and consternation
As the Happy Time waned, it was becoming apparent that Britain was developing better technology and defences against the wolfpacks, while the Kriegsmarine continued to emphasise tactics. In addition to ASDIC, better training of convoy escort crews, the proliferation of shipboard radar, the commitment of long-range aircraft from Royal Air Force Coastal Command and later the US Navy and Air Forces, and the development of better weapons such as the ‘Hedgehog’ contributed to mounting U-boat
losses. The Hedgehog, which threw up to 24 bomblets in a pattern to increase the likelihood of a hit, was introduced in 1942 and credited with sinking 47 U-boats. Hunter-killer groups were formed to search and destroy U-boats – the one-time hunters becoming the quarry.
One of the most significant anti-submarine defences introduced was High Frequency Direction Finding, or Huff-duff, which utilised intercepted U-boat radio traffic, usually between boats at sea and headquarters, to pinpoint the positions of enemy submarines. Huff-duff employed two frequency interception locations, land-based or at sea, assessing the slightly different signals to determine a bearing. By the summer of 1942 U-boats were being caught on the surface at night without warning. Suddenly the ominous buzz of aircraft engines would be heard, the powerful 22-million candela Leigh Light stabbed through the darkness, and the illuminated submarine was pounded by bombs and riddled with machine gun fire. In the month of July, 12 U-boats were sunk. Nine were sent to the bottom in August, and during the next three months 39 were destroyed. Huff-duff is believed to have contributed to nearly 25 per cent of all U-boat sinkings.
Eventually, as the number and expertise of convoy escorts and the deployment of improved anti-submarine defences continued to increase, U-boat losses reached staggering and unsustainable proportions. While 86 U-boats were lost in 1942, losses nearly tripled in 1943 to 241, with 42 in May alone and 38 in July. A total of 234 U-boats sunk or scuttled in 1944. Compounding the difficulties for the U-boats, British cryptanalysts had managed to break the German radio communications encrypted with the Enigma machine.
The capture of U-110 along with an intact Enigma machine and other cryptologic information by the destroyers HMS Bulldog and HMS Broadway and the corvette HMS Aubretia on 9 May 1941 facilitated the breakthrough. Lemp, captain of U-110, was shot dead by a member of the Royal Navy boarding party.
The decrypted German messages were given the code name ‘Ultra’, and by July the first application of Ultra intelligence contributed to a dramatic drop in merchant tonnage lost – from over 310,000 in June to 94,209.
From drumbeat to destruction
As Dönitz repeatedly tried to establish U-boat ‘critical mass’ in the North Atlantic, the demands for support of operations in North Africa diverted strength from the primary effort. While results improved dramatically, with 292,829 tons sunk in September 1941 as U-boats attacked convoys bound to and from Gibraltar, the gateway to the Mediterranean was also the scene of the first dramatic, clearcut British victory over a U-boat wolfpack.
In December 1941 Convoy HG 76, bound for the British Isles from Gibraltar under the protection of the 36th Escort Group, was set
upon by a wolfpack soon after clearing the harbour. A four-day running battle ensued. Captain Johnnie Walker led the 17 escort vessels, including the escort aircraft carrier Audacity. On the morning of the 17 December U-131 was sunk in a combined effort of aircraft from Audacity and escort vessels. The next day U-434 was sunk. Shortly afterwards, U-574 torpedoed and sank the destroyer HMS Stanley. Walker’s own ship, the sloop Stork, rammed and sank U-574. For good measure, the escorts sank U-567 the next day. Partially due to the incompetence of its captain, Audacity was torpedoed and sunk by U-751 on 21 December.
Despite the loss of Audacity and Stanley, five U-boats – half the attacking wolfpack
– had been sunk, and other U-boats had sustained damage. Only two of the 32 HG 76 merchantmen were sunk. After news of the defeat reached Dönitz, 1941 ended amid an air of gloom at U-boat headquarters.
After US entry into World War II on 11 December 1941 a handful of U-boats were dispatched to the east coast of the United States, and for a period of several months wreaked havoc on American shipping. The US was totally unprepared to defend against submarines. Dubbed
Operation Drumbeat, the U-boat assault devastated merchant shipping from New England to
Florida and into the Caribbean. In
March 1942 95 ships were sunk, totalling over 530,000 tons. When the US Navy and Coast Guard finally implemented the convoy system, enforced blackout rules and stepped up coastal patrols, the diminishing return compelled Dönitz to recall his wolves. During the ‘Second
Happy Time’ from January to August
1942, U-boats sank 609 ships carrying 3.1 million tons of cargo.
Redoubled American antisubmarine efforts helped to account for the sinking of 86
U-boats in 1942.
In the autumn of that year wolfpacks scored renewed successes in the Atlantic and Mediterranean. Convoy escorts were fewer due to the demands of
“THE MEDITERRANEAN WAS ALSO THE SCENE OF THE FIRST DRAMATIC, CLEAR-CUT BRITISH VICTORY OVER A U-BOAT WOLFPACK”
Operation Torch, the Allied invasion of North Africa. Wolfpacks ravaged convoys in October and November, sinking more than 100 ships in each month and destroying 619,417 and 729,160 tons of shipping respectively. The November total was an all-time high.
In early 1943 pitched battles raged across the mid-atlantic and the Western Approaches. Convoys were particularly vulnerable while sailing through the Mid-atlantic Gap, also known as the ‘Black Hole’, an expanse of ocean initially beyond the range of RAF Coastal Command air cover. Before the gap was closed with longer-range aircraft that spring, losses were at times prohibitive. In February and March 1943 U-boats sank 359,328 and 627,377 tons of shipping in the Atlantic. However, 18 U-boats were destroyed in February alone.
The realisation that the U-boat war against the Allies was lost came abruptly. Within weeks of the spring triumphs, roles were reversed. In May 1943 Dönitz lost a staggering 41 U-boats while only 264,853 tons of shipping was sunk. Such losses were unsustainable, and the wolfpacks were recalled. Although the Allies had won the Battle of the Atlantic, German submarines continued to fight and periodically claimed Pyrrhic victories right up until the end of the war.
Whither the wolfpack
The legend and lore of the wolfpack conjures up great tales of danger and derring-do. Despite Churchill’s concerns, a closer look at wolfpack performances may lead observers to draw conclusions that are markedly different from those a post-war generation of historians has traditionally embraced.
U-boat forays were never mounted in war-winning numbers, although in the spring of 1941 their sorties were enough to raise considerable concern. Dönitz placed his emphasis on tactical solutions to problems, while the implications and benefits of overarching technological advances apparently escaped him, ultimately proving fatal to the wolfpack offensive.
While they concentrated U-boat striking power, wolfpacks also presented multiple targets in a compact operational zone as convoy escorts and other countermeasures steadily grew in lethality. Wolfpack operations depended on radio communication, often compromising surprise and summoning swift retribution. Torpedo malfunctions and limited improvements in U-boat technical performance drove Dönitz and his senior commanders, as well as captains and crews with their lives on the line, to distraction. Then there was the vastness of the Atlantic itself. Allied convoys could still sail the sea undetected. Opportunities were lost and with them the Battle of the Atlantic.
The numbers speak for themselves. Captured U-boat war diaries revealed the startling reality that many German submarines spent entire patrols without making contact with a convoy. Fewer than 800 combat patrols – under 30 per cent of the 2,700 sorties conducted – actually produced contact. Only 30 of nearly 3,300 merchantmen bound for British ports were sunk during the first eight months of 1942. During the first 42 months of the war, over 70 per cent of the ships sunk by U-boats were either sailing alone or lagging behind their assigned convoys. Of the 620 ships sunk while transiting in convoys, only 16 were lost when the convoys were protected by both naval escort and air cover. In sharp contrast, 65 per cent of all U-boat losses in World War II were inflicted by convoy escorts.
Without doubt, the wolfpack earned its place in history. However, an unbiased evaluation of its performance strongly suggests a less than stellar record – one that never really brought Britain to the brink of defeat. Nevertheless, the exploits and sacrifice of those who fought the Battle of the Atlantic, both Allied and Axis, raised the wolfpack to mythical status, and these intrepid men are worthy of remembrance.
“U-BOAT FORAYS WERE NEVER MOUNTED IN WAR-WINNING NUMBERS, ALTHOUGH IN THE SPRING OF 1941 THEIR SORTIES WERE ENOUGH TO RAISE CONSIDERABLE CONCERN”