Origins of THE wolfpack
The very mention of this infamous tactic conjures images of U-boats massacring merchant convoys. But what was the reality of Dönitz’s plan and from where did his idea originate?
The origins of Karl Dönitz’s fearsome ‘Rudeltaktik’ – anglicised as ‘wolfpack tactics’ – can rightly be attributed to the Führer der Unterseeboote (FDU, Commander of Submarines) of the previous war – Fregattenkapitän Hermann Bauer. Bauer maximised the potential of this new weapon in the naval arsenal, his U-boats achieving great success, bringing Britain’s merchant shipping balance to near bankruptcy in the first half of 1917. This was achieved with U-boats operating independent of one another or any centralised control. Such fearsome losses prompted the British Admiralty to introduce convoying during that year as a means of ‘collective defence’. In response Bauer submitted a proposal to the German naval staff that U-boats alter tactics and be co-ordinated and concentrated on crucial inbound British convoys. He intended to achieve this level of control by means of a large radio-equipped transport U-boat of the Deutschland class that could operate as a mobile command centre at sea. Staffed by trained wireless and decryption personnel, this U-boat would monitor British radio signals to anticipate convoy movements and direct accompanying combat boats to intercept enmasse. However, despite Bauer’s sound logic, the proposal was rejected.
Ultimately the First World War U-boats were defeated, though their subjugation was no means a decisive Allied victory as just under half of the operational U-boats that had been built remained combat-ready in November 1918. It was not only improved enemy anti-submarine warfare techniques and the introduction of escorted convoys that had beaten their campaign. Germany’s U-boats lacked a powerful charismatic leader capable of forging fresh tactics, rather than accepting the status quo, particularly after Bauer’s replacement in June 1917.
While true that the technical limitations of radio equipment aboard the First World
War U-boats severely hindered inter-boat cooperation at sea, there were localised efforts at coordinating attacks. One such attempt took place in the Mediterranean during October 1918 when skippers of two U-boats of the Pola Flotilla planned to sail and rendezvous on 3 October, 50 miles from Sicily’s south-eastern corner. There they expected to intercept Allied convoy traffic from the east. However, one boat’s departure was delayed by urgent repair work and only UB68 sailed as planned.
This U-boat encountered the enemy on 4 October, sinking 3,883-ton British steamer SS Oopack before being forced to dive by escort ships. Sudden technical problems resulted in a loss of control, and the boat plunged below its maximum rated depth. It was only saved by the commander ordering the ballast tanks be blown, bringing UB68 hurtling to the surface amidst the convoy it had just attacked. Illuminated by flares and searchlights, UB68 was shelled and sunk with four men killed and 33 captured. The young skipper, Oberleutnant zur See Karl Dönitz, was among the survivors:
“In October 1918 I was captain of a submarine in the Mediterranean near Malta. On a dark night I met a British convoy with cruisers and destroyers. I attacked and I sank a ship, but the chance would have been greater if there had been a lot of submarines. That’s why the idea of a wolfpack, to put the submarines together so they could attack together, was very impressive. That’s why, in all the years from 1918 to 1935 when we had the first submarines again in the German navy, I had never forgotten this idea.”
Following Hitler’s rise to power the German navy was resurgent and in September
1935 Kapitän zur See Dönitz was placed in command of the ‘Weddigen’ flotilla of small Type II coastal boats. He did not hold the post for long, promoted to FDU within the new Kriegsmarine during the following January, and later to BDU, (Befehlshaber der Unterseeboote, Commander-in-chief Submarines).
Dönitz threw himself into development of a fresh tactical doctrine for undersea warfare, centred on his wolfpack theories of coordinated group attacks. This technique was first used in large-scale Wehrmacht exercises during the autumn of 1937.
From the U-boat depot ship Saar Dönitz directed several U-boats in locating an ‘enemy’ convoy, gathering and then launching an ‘attack’, all with impressive results. Dönitz instructed his youthful skippers to strike with torpedoes while running surfaced at night, using the U-boat’s high surface speed, manoeuvrability, and low profile to its fullest advantage. Radar was extremely uncommon on enemy ships at that time and, by this method, British ASDIC location sonar was also rendered useless. The Baltic was too small for Dönitz to fully test his theories on group operations, but repeated requests for permission to stage Atlantic exercises were refused, lest British and French naval authorities misconstrue the presence of U-boats in any strength within the Atlantic while the Spanish Civil War raged. Not until May 1939 did a small number of U-boats undertake any such exercises in the North Sea and, later, west of the Iberian Peninsula.
Though feeling justified in his faith in the wolfpack there remained unanswered questions centred on the two pillars of his theory: control and communications. Was it possible to simultaneously exert command over several U-boats? Did they require authority exercised by an officer at sea? Was it possible to do so from another U-boat or a surface vessel or was it possible from a land-based station?
How best to communicate with U-boats when surfaced, at periscope depth or deeper? Finally he still pondered the tactical considerations of
“AERIAL RECONNAISSANCE RARELY BECAME A CONTRIBUTING FACTOR TO U-BOAT SUCCESS, DESPITE DÖNITZ’S BEST EFFORTS TO COOPERATE WITH THE LUFTWAFFE FOR THIS PURPOSE”
exactly how the U-boats should initially operate – as a group or scattered and summoned to a rendezvous in the event of convoy contact?
Effective reconnaissance was an important prerequisite for any attempted wolfpack operation. The patrol line became the tried and tested method by which echeloned U-boats travelled in parallel with just over two times the radius of visual distance between them. By this method they could, theoretically, comb the ocean to locate the enemy.
In reality, of course, the patrol line was subject to the detrimental effects of bad weather, faulty navigation and flawed intelligence. Aerial reconnaissance rarely became a contributing factor to U-boat success despite Dönitz’s best efforts to co-operate with the Luftwaffe for this purpose. Despite eventually being granted control over the bombers of KG40, imperfect Luftwaffe maritime navigation and a lack of aircraft would serve to neuter the effort. The patrol line remained king, requiring many operational U-boats available to make it truly viable. Dönitz reasoned on needing 300 front-line boats by the time of any conflict. This number meant at any one time 100 could be outbound, 100 on station and the last 100 returning for replenishment. As war with Britain and France began in September 1939 newly promoted Kommodore Karl Dönitz went to battle with a grand total of 57 U-boats, 18 of which were available for Atlantic patrols.
The first wolfpacks
The U-boats’ opening salvos were generally against ships travelling solo, though British defensive convoying measures began almost immediately. After less than a week of war Dönitz withdrew ten of his most modern
Atlantic boats to prepare for his first wolfpack operation against a predicted increase in convoy traffic during October. Unfortunately his originally intended scale of attack was reduced somewhat by U-boats ordered by naval staff for special assignment or unexpected delays in dockyard repair. Ultimately, only a small force of six U-boats was available for the first attempted wolfpack. The group’s tactical commander afloat would be Korvettenkapitän Werner Hartmann, senior officer of the Hundius Flotilla and skipper of U37, while Dönitz retained operational command. Hartmann would be accompanied by U40, U42, U45, U46 and U48.
“I have decided to operate the boats against Gibraltar traffic… Success will depend on the boats making a surprise appearance together. They will be ready on different dates and will therefore sail on different days and will occupy an operations area southwest of Ireland, which sinking figures so far have shown to be the best area. When all the boats have arrived there, they will receive orders to proceed… Hartmann will be in U37 as senior officer of this Atlantic group and he will, if necessary, take over control in convoy operations.
“If he finds things are not promising off Gibraltar, he will be authorised to order a new disposition, rather further from the enemy bases, along the west coast of Spain and Portugal. Only north-south bound merchant ships would be picked up here, of course.”
The results were best described as mixed. Three of the U-boats were lost as the group assembled, though none as a direct result
“THE ACQUISITION OF CONQUERED FRENCH PORTS GRANTED DÖNITZ IMPRESSIVE FORWARD BASES WHICH SOON HOSTED U-BOAT FLOTILLAS AND NEW GERMAN INFRASTRUCTURE WITHIN FIVE MAJOR ATLANTIC PORTS”
of the pack operation. U40, the last of the group to leave port on 10 October, was sunk in a minefield east of Dover after attempting to shortcut its way to the Atlantic through the English Channel while both U42 and U45 were sunk by escorts during independent action against convoys.
The remaining three boats subsequently experienced some measure of success in a group action against convoy HG3, spotted by lookouts aboard U46 at 8.51am on 17 October. Kapitänleutnant Herbert Sohler briefly lost contact with the merchant ships before sweeping the area and reacquiring the northbound merchant ships sailing under weak escort. U46 shadowed HG3 at a distance until that afternoon when permission to attack was received. Each U-boat sank a single ship before the remainder scattered and managed to shake off pursuit.
Hartmann ordered a reconnaissance line formed, but aircraft deterred pursuit and Hartmann as tactical commander instructed the boats to move towards position ‘Schwartz’ off Portugal. U48, now bereft of torpedoes, was ordered home while U46, with limited fuel, achieved nothing more. U37 sank four independently sailing ships.
Though hardly an unqualified success, convoy HG3 had been successfully attacked, but six reported torpedo failures possibly prevented greater achievement. Though it was perhaps telling that both U37 and U48 had experienced far greater success independently of the group, a second wolfpack operation was to be made during the following month.
This time five U-boats were to once again assemble south of Ireland before sweeping towards Cape Finisterre. Unfortunately, this number was also whittled down to just three.
Gales off Ireland forced the boats towards the approaches to Gibraltar where they homed in on shadowing reports from U53 of a convoy northwest of El Ferrol, making contact and attacking. U49 was swiftly damaged by depth charges and forced away, while the remaining boats had no success over a three-day chase, later sinking independently sailing merchants once the group was dispersed by Dönitz. It was clear that the number of U-boats at sea was insufficient for effective wolfpack actions, while the method of control and coordination required further analysis, and Dönitz suspended further group operations.
The wolfpacks return
Dönitz’s U-boats resumed individual torpedo and minelaying missions that harvested a steady toll of British ships. The invasion of Norway in April 1940 absorbed virtually all U-boat strength and subsequent dockyard congestion delayed a return in force to the Atlantic until the end of May with the fall of France imminent.
During that month U-boat construction and the simultaneous return to service of many refitted after the Norwegian campaign finally gave Dönitz enough operational boats to attempt renewed wolfpack missions during June 1940. Kriegsmarine radio intelligence (B-dienst) reported on 12 June that the heavily escorted fast convoy US3, comprising six passenger liners including the Queen Mary
and Mauretania carrying 26,000 Australian and New Zealand troops, had arrived in the Freetown sea area.
Simultaneously the same intelligence source revealed detailed information about merchant convoy HX48 entering the Western Approaches and due to rendezvous with its local escort. In coded messages from Berlin, ‘Group Rösing’ was formed of five U-boats centred around U48 with skipper Korvettenkapitän Hans-rudolf Rösing, senior officer of 7th U-flotilla, as tactical commander, to intercept US3. ‘Group Prien’ was then assembled in a reconnaissance line of six boats through which HX48 was expected to pass with U47 and Kapitänleutnant Günther Prien in tactical command. All boats were ordered to maintain radio silence, though neither contacted their target convoys and were dispersed to resume independent operations. Although radio intelligence from the B-dienst service continued to provide accurate and valuable information, the limited visual range of lookouts atop a low U-boat conning tower proved an insurmountable obstacle.
Meanwhile the acquisition of conquered French ports granted Dönitz impressive forward bases which soon hosted U-boat flotillas and new German infrastructure within five major Atlantic ports. French bases also increased available shipyard capacity, reduced transit time to and from the Atlantic battleground and therefore, in theory, boosting the number of combat boats at sea.
Furthermore Germany now also had possession of several powerful land-based radio transmitters on the French Atlantic coast, most notably the very low frequency (VLF) stations at Croix Dhins and Basse Lande which augmented the existing transmitter situated in Nauen near Berlin.
Very low frequency signals were capable of transmitting one-way wireless messages to submerged U-boats, though the depth at which they could receive such signals was dependant on distance, power of the radio signal, the frequency used and salinity of the sea water. In general an absolute maximum of 20 metres could be reached before contact was lost.
The long antenna required to transmit VLF signals could not be accommodated aboard a U-boat and they were therefore unable to reciprocate a message without surfacing to transmit in high frequency.
However this proved somewhat beneficial as U-boats were invisible to radar if submerged and impervious to Allied direction finders if not transmitting, maximising their greatest advantage – invisibility.
In the interim Dönitz, now headquartered in 18 Boulevard Souchet, Paris, had further refined his wolfpack tactics. With the increased radio capability, he believed that the U-boats were best coordinated from the land headquarters. A tactical commander afloat was no longer considered necessary and had proved inefficient in the past as the tactical leader’s boat had sometimes been compelled to dive by enemy escorts, immediately leaving the remaining U-boats leaderless. Constant tactical control from the situation room at BDU remained the logical solution.
Furthermore Dönitz’s new doctrine relied on the contacting U-boat to shadow its convoy without attacking while BDU coordinated the deployment of other boats to form the wolfpack at sea. Cooperation between the U-boats themselves was maintained by visual signals if possible, or radio watches on a pre-arranged shortwave frequency. BDU would re-transmit at fixed times any messages received from U-boats, allowing all in a group to maintain an overall view of each other’s movements. Once in position, BDU would grant permission to attack, with each skipper then acting independently once the action had begun.
With many British destroyers held back in home waters to counter the threat of German invasion, escort numbers decreased, providing fortuitous timing for Dönitz as he opened a new wave of wolfpack attacks in 1940. Success grew exponentially. In September Prien’s U47 found HX72 while on weather reporting duty and low on ammunition at the end of a successful patrol. As he shadowed Dönitz quickly assembled the experienced skippers of U99, U48, U65, U38, U43, U32 and U100 to attack and together they sank 11 of the 41 merchant ships at no loss to themselves. It was a good beginning but it would be the following month that the pinnacle of wolfpack achievement was reached.
After briefly being sighted and reported by U48 on the night of 16 October, the slow SC7 convoy of heavily laden merchants shook its shadower free before being reacquired by
U38 the following day. The convoy had left
Nova Scotia eleven days previously bound for Liverpool, a planned speed of 8 knots reduced after many older, smaller vessels proved incapable of this pace.
Thirty-five merchant ships departed Canada, but almost immediately some straggled as bad weather separated them from the main body and two subsequently sank while sailing alone. A pair of Royal Navy sloops and a single
corvette were in escort as the first torpedoes hit. Dönitz had gathered U38, U46, U48, U99, U100, U101 and U123 as SC7 sailed directly into the U-boat patrol line. Within three nights one of the bloodiest convoy battles of the war was fought and resulted in unmitigated disaster for the Allies. In total they lost 20 merchant ships, with a further two damaged, and in return experienced no success against the attacking U-boats. One hundred and forty-one merchant sailors were killed in what the German newspapers quickly dubbed ‘The Night of the Long Knives’. Action was broken off as the shattered remnants of SC7 reached the comparative safety of the North Channel. While some U-boats already departed after exhausting their torpedoes, others diverted to strike convoy HX79, which also lost 12 ships and two others damaged before the attackers ran completely out of ammunition.
The ‘Happy Time’
The wolfpack theory that Dönitz had nurtured since his own days in combat was finally fully vindicated. Nonetheless challenges remained. The nautical area required to enable surfaced U-boats to assemble an effective patrol line had moved the boats further west into the Atlantic Ocean away from the heavily patrolled and constricted North Channel and its approach to Liverpool. This placed expected convoy interception points in the open ocean, also allowing them to effectively reroute around any detected U-boat concentration. Locating the convoys became perhaps the biggest problem for the wolfpacks with negligible Luftwaffe assistance and too few Atlantic U-boats.
Nonetheless the period between July 1940 and March 1941 when the wolfpacks truly began to bite has often been referred to as the ‘Happy Time’ for U-boat crews. But at least one of the veterans involved recalled this entire period in a completely different light.
Otto Kretschmer, the highest ‘scoring’ U-boat ace of the Second World War remembered,
“The ‘Happy Time.’ I don’t like this term. We were the first ones to probe the defences of the enemy and this was not a happy time because 50 per cent of our forces perished. I remember when I was with U99 and went into the Atlantic for the first time, I found out that before me there were six submarines sent to the Atlantic and three were sunk. Fifty per cent losses. So, this is called the ‘Happy Time’? I don’t know why. And, of course, we had been trained during peace time and we had to discover whether the peace time tactics were any good for war, which they were not at all times… The ‘Happy Time’ had been invented by Propaganda Kompanie in Germany; they were the first to speak about it.”
Though undoubtedly a sound tactical doctrine, the real success of the wolfpacks primarily resulted from the tenacity and bravery of the U-boat commanders at a time when Allied defences were undeveloped and understrength. ‘Aces’ such as Kretschmer, Joachim Schepke (U99), Günther Prien (U47) and Herbert Schültze (U48) piloted their
U-boats at speed inside the convoy body, running surfaced and firing to left and right.
This fearless aggression sank dozens of Allied ships, but it was soon exhausted by veteran commanders transferred to larger ocean-going long-distance U-boats, moved ashore to train the next generation of skippers, or lost in action.
In March 1941, three of those most famous U-boat skippers – Kretschmer, Prien and Schepke – were all lost.
Although the wolfpacks were far from defeated and their depredations of Allied shipping would continue into 1943, the real ‘Happy Time’ of the wolfpacks was already over. While they continued to operate until 1943, they would rarely achieve such convincing results as during the latter half of 1940.