Wolf Packs at War: The U-Boat Experience in the Second World War (Unterseeboot) Experience

The Second World War demonstrated to the entire world the strategic importance of submarine warfare and its profound impact on humanity. One of the most striking elements of this war was the German U-Boats (submarines) and their ‘Wolf Pack’ tactic, which carried out devastating attacks against Allied convoys, particularly in the Atlantic Ocean.

The term ‘U-Boat’ is an abbreviation of the German word “Unterseeboot” and has been translated into Turkish as ‘denizaltı’. However, this translation has a general meaning; in a historical context, it specifically refers to the military submarines used by the German Navy (Kriegsmarine) during the Second World War.

Approximately 1,171 U-Boats were operational during World War II. Only 325 of these attacked enemy ships; over 800 were used solely for training purposes or were unable to locate and attack the enemy. Allied losses due to U-Boat attacks amounted to approximately 3,000 ships and over 14,000,000 tonnes. Over 70,000 people died. Nearly 70% of all Allied ship losses were attributed to U-boat attacks. The vast majority of these losses (over 2,600 ships) resulted from torpedo attacks or a combination of torpedoes and subsequent gunfire.

German U-Boat Types: The Shadow Warriors of World War II

Developed by the German Kriegsmarine, U-boats (Unterseeboot) were among the strategic assets that shaped the course of naval warfare throughout World War II. Below are brief technical and historical descriptions of the prominent U-boat types of the era:

Type VIIC Forming the backbone of the Atlantic War, the Type VIIC was the most widely used and most produced submarine class throughout the war. Its durability, range and torpedo capacity made it a key element in the ‘Wolfpack’ tactics used against Allied convoys.

Type IXD2 Represented by examples such as U-177, the Type IXD2 were large-tonnage submarines designed for long-range operations. Operating particularly off the coasts of Africa and South America, they symbolised the global reach of German naval power.

Type XIV (‘Milchkuh’) Represented by submarines such as U-460, the Type XIV were supply submarines that provided other U-Boats with fuel, ammunition, water, and provisions during the war. They even had their own ovens, enabling them to serve fresh bread to the submarines they supplied. This ‘Milk Cow’ class played a critical logistical role in ensuring operational continuity.

Type XXI (‘Elektroboot’) Developed towards the end of the war, the Type XXI featured a design that was ahead of its time. Thanks to its advanced battery systems and underwater speeds, it is considered the first truly modern submarine. However, their operational impact was limited as they entered service near the end of the war.

Type XB (Minitelayer) The Type XB class consisted of large submarines specifically designed for sea mine laying duties. They aimed to disrupt Allied maritime traffic through mine-laying operations in strategic harbours and straits.

Design and Technical Specifications of Type VIIC U-Boats

Internal Structure:

The Type VIIC submarine consists of basic compartments such as torpedo rooms (bow and stern), control room, diesel and electric motor rooms, crew quarters, toilet and radio room. Each compartment is designed to perform a specific function. For example, the control room (central control room) is reserved for the submarine commander and underwater radio and sound equipment.

Armament:

Type VIIC submarines were generally equipped with 20mm or 37mm anti-aircraft guns, 88mm or 105mm naval guns (in some types), and torpedo tubes (4 forward, 1 aft). ‘Four forward torpedo tubes and one aft torpedo tube’ was the standard configuration.

Size and Capacity:

Larger submarines, such as the U177, were designed to offer their crew a ‘higher standard of comfort.’ This demonstrates the importance of living conditions during long-range missions. The U177's ability to operate for extended periods, such as ‘183 days in the Indian Ocean,’ is an example of this capacity.

U-Boat: A Technical Marvel and a Confined Living Space

U-Boats are important examples of Second World War submarine technology. A typical submarine, such as the Type VIIC, contained various compartments, including a bow torpedo room, control room, galley, diesel engine room, and stern torpedo room. The interior housed essential living and operational areas, such as batteries, the commander's control room, radio direction finder, officer and crew living quarters, and toilets.

However, not all U-boats were the same. For example, U177 was a much larger Type IXD2 vessel, built by Deschimag AG Weser in Bremen and used by Commander Robert Gysae, who preferred a high standard of comfort. This submarine operated in the South Atlantic and Indian Ocean, with its longest voyage lasting 183 days. During such long voyages, the difficulties of submarine life were compounded by conditions where the crew could hardly ever see the sky and were unable to exercise properly. Some U-boats, such as U-235, had diesel engine compartments that were quite noisy and featured special flashlight installations to speed up repairs. This demonstrates that U-boats were not only war machines but also technically and psychologically challenging living spaces for the crew.

Training the U-Boat Crew: The Wild Experience of the Seas

The training of the U-boat crew played a vital role in preparing them for their demanding duties. Early U-boat training was quite excellent, but the programme has changed over time.

During the training process, the crew was expected to possess not only technical knowledge but also survival skills and psychological resilience. The example of U253 illustrates this training and the harsh realities of war. Under the command of Kptlt Adolf Friedrichs, U253 began service on 21 October 1942 and embarked on its first operational voyage from Kiel on 22 January 1943, only to be lost two weeks later with no survivors. Such losses underscored the dangers the crew faced at any moment.

Cover image: German submarine U-1004 was a Type VIIC/41 U-boat built for the Kriegsmarine of Nazi Germany during World War II. It was laid down as ship number 204 at the Blohm & Voss shipyard in Hamburg on 15 January 1943, launched on 27 October 1943, and commissioned on 16 December 1943 under the command of Lieutenant zur See Hartmuth Schimmelpfennig. It was sunk by naval gunfire on 1 December 1945 at position 56.10N x 10.05E (Norway).

Crew Life and Conditions on U-Boats in Type VIIC:

Life on U-Boats was characterised by cramped and harsh conditions. The crew had to demonstrate physical and psychological endurance during long-term missions.

Living Space:

The ammunition for the U-boat's weapon systems had to be squeezed into very limited spaces due to structural volume constraints. Since most of the internal volume was allocated to the propulsion system, battery compartments, and torpedo tubes, ammunition and food storage areas were given secondary priority in the design.

Food storage capacity is insufficient when considering long mission durations. To compensate for this deficiency, in some submarines, one of the toilets has been removed and repurposed as a pantry. Such solutions significantly reduce the ergonomics of the living space and challenge the psychological resilience of the crew. U-Boat design is a constant search for balance between military effectiveness and the human factor. Operational requirements such as weapon capacity and range have been prioritised at the expense of living comfort and sustainability. This situation clearly demonstrates that engineering decisions have not only technical but also ethical and human dimensions.

Lack of Hygiene and Comfort:

The crew faced conditions where ‘toilet and bathing facilities were primitive’ and ‘there was not enough space to lie down even for an hour.’ Some captains chose to remove one of the drinking and service water tanks and use it as a fuel tank to increase operational range.

This practice suggests that water purification systems were not used; it directly affected the crew's basic needs, making it impossible for them to bathe. This situation compounded the difficulties of long missions.

Morale and Discipline:

Maintaining crew morale and discipline was of vital importance. Scholl's experiences on U48, in particular, demonstrate continued discipline and commitment despite these difficulties, stating that ‘most of the crew members were physically and mentally exhausted.’

Losses and Danger:

U-Boat operations were extremely dangerous, and crew losses were high.

Life on a U-Boat: Survival and Psychological Costs

Living conditions on U-Boats were extremely harsh. The atmosphere inside the submarine was generally poor; there was a foul smell, dampness and a lack of adequate air circulation. The crowded conditions, lack of personal space and constant sense of danger placed a huge psychological burden on the crew. Sources describe the U-boat crew as individuals detached from the chaotic environment of war, driven solely by the instinct to survive. Records kept by Waldemar Schlipp, a U-boat biographer, indicate that the crew sometimes returned with exaggerated or ‘unrealistic stories’.

The crew's state of mind and philosophy of survival was summed up in these words: ‘Once you have expended all your energy on the basic process of survival, then you must disperse your emotions or you will perish.’ These words reflect the crew's inner warrior spirit and their struggle to find the last ounce of energy to survive, even in barbaric conditions. The events of an attack on 10 October 1942 clearly demonstrate the chaos and horror created by depth charge attacks on submarines: explosions, screams and moments of terror.

U-Boat Attacks and Operational Difficulties:

U-Boats were designed to attack enemy convoys and play a significant role in the Battle of the Atlantic. However, these operations were fraught with a series of technical and environmental difficulties.

Wolfpack Tactics:

One of the most well-known tactics of the U-Boats was the ‘Wolfpacks,’ which involved coordinated attacks on convoys. However, these tactics became less effective as detection systems and countermeasures developed.

Navigation and Detection:

The operational success of the U-Boats depended on their ability to navigate accurately and detect the enemy. However, ‘too much visibility was not a welcome thing for a submarine.’ Daytime attacks or periods spent on the surface increased the risk of detection.

Balancing Difficulties:

It has been noted that submarines ‘struggled to maintain balance after firing a torpedo.’ This was a complex engineering problem that required the crew to react quickly and restore balance.

Weather Conditions:

‘Bad weather’ greatly affected U-boat operations. In particular, ‘foggy weather, such as on 16 October 1942,’ could alter or cancel attack plans.

Depth charge attacks:

These were one of the greatest threats to U-boats. Enemy ships could detect the sounds made by U-boats via hydrophones (underwater microphones) and determine their location. Commanders such as Schultze had witnessed such detections in the Mediterranean. The constant threat of detection and attack kept the crew under immense pressure. Allied sonar technology, however, was far from operating at the desired level.

In these long-range operations, problems such as mechanical failures, supply shortages, and encounters with enemy aircraft were common. Continuous training and improvement for the crew was critical to overcoming these difficulties. Chaotic situations involving depth charges, collisions, and damage resulted in the loss of even the best U-boats and experienced crews.

Bases and Returns: Rest and Confronting Reality

Bases served as a respite and re-provisioning point for U-boats after long and arduous patrols. At bases like the Tirpitz Pier in Kiel and the Kiel Canal, U-boats underwent maintenance, and crews found opportunities to rest. However, living conditions at bases still showed marked differences between officers and enlisted personnel.

While officers had ‘fairly comfortable camps’ and ‘more private rooms,’ the crew usually stayed in ‘shared rooms or dormitory-like quarters,’ having to share facilities such as bathrooms, laundries, and toilets. This situation demonstrated that the hierarchy within the submarine continued in life on land. Repair and resupply facilities at bases were of vital importance.

Tactics Used by U-Boats

The Prize Rules and the Early Stages of the War:

At the beginning of the war, Hitler ordered U-Boats to operate according to the “Prize Rules”. These rules required the safe evacuation of passengers, crew, and ship's papers before a merchant vessel was sunk. These rules created significant difficulties for U-boats: ‘Placing the crew in lifeboats was not sufficient to comply with these rules, as there was no guarantee that survivors would be picked up later.’ Furthermore, the risk of merchant ships attacking U-boats or sending warning signals made lengthy stopping and searching procedures impossible. The restrictions were gradually eased; although the Prize Rules remained largely in force until August 1940, ships travelling in convoy were soon considered ‘legitimate targets’.

Lone Hunters and Convoy Systems:

Early in the war, U-boats typically operated alone, though this was partly a necessity due to their small numbers. The convoy system had been introduced at the start of the war, but the lack of sufficient escort vessels meant that most merchant ships sailed independently.

Night Surface Attacks:

During the first half of the war, night surface attacks were highly successful because the low profile of U-boats made them difficult to detect in the dark. This tactic allowed U-boats to approach convoys, and even infiltrate them, without being detected by escort vessels. This helped aces such as Otto Kretschmer achieve their ‘one torpedo - one ship’ objective. However, as the war progressed, such sinkings decreased due to ‘a significantly increased chance of being detected on the surface by enemy aircraft or surface vessels’.

Wolf Pack Tactics:

The “Wolf Pack” tactic was an extremely effective strategy used by U-boats against convoys during World War II. This tactic relied on submarines attacking in a coordinated group rather than conducting individual operations.

How the Tactic Worked

● When a U-boat detected the location of a convoy, it relayed the information to other submarines within range.

● Upon receiving this message, the other U-boats moved into the most suitable positions for attack, surrounding the convoy.

● Attacks on the convoy from multiple submarines simultaneously at different points overwhelmed the escort vessels protecting the convoy. While the escort vessels focused on the attack and attempted to take up position, they would be confronted with news of a new attack from another point of the convoy.

● This tactic made the protection task even more difficult, especially for convoys with few escort vessels. This situation significantly increased the success rate of U-boat attacks. A number of Type VII submarines were also equipped with a Balcongerät (Balcony Apparatus), which was mounted on a ‘balcony’-shaped cover at the lower part of the bow. This apparatus provided an effective area for the more efficient operation of both the GHG (earlier-stage sound detection) and KDB (sound detection) systems. In the small radio room, underwater acoustic detection equipment listened for the sounds made by enemy ships' propellers. Although sound travels long distances underwater, various conditions, such as the salinity of the water, could affect the equipment's efficiency.

An experienced Unterwasserhorcher (sound detector operator) could distinguish between the sound of a slow-moving merchant ship and the sound of the faster-turning propellers of accompanying warships. Although U-boats operated independently before and after an attack, the ‘swarm’ concept only came into play at the moment of attack.

This strategy was systematically developed by the Commander of the German Navy, Karl Dönitz, from 1941 onwards and transformed into a standard operational plan. Typically, a series of submarines would spread out along the convoy's expected route to form a patrol line, and when the lead submarine located the convoy, the entire pack would spring into action.

This tactic seriously threatened the Allies' logistical lines in the Atlantic, but it gradually lost its effectiveness due to counter-tactics developed by Allied air and naval forces.

Operations and Missions

1939: The Start of the War In August 1939, only 18 U-boats were at sea. In October 1939, the first recorded group attack saw six U-boats sent to intercept British convoys. Three merchant ships were sunk, but three U-boats were also lost. By the end of the year, 147 enemy ships had been sunk, 100 of which were sailing independently. No U-boats were lost during this period.

1940: The First ‘Happy Time’ Between January and May 1940, 126 Allied ships were sunk. Torpedo problems during Operation Weserübung (the invasion of Norway) prevented many potential sinkings. The capture of France provided bases that gave U-boats direct access to the Atlantic and increased their range. The period between June and December 1940 is known as the ‘first “Happy Time”’ and saw over 360 enemy ships (approximately 2,000,000 tonnes) sunk. Major convoy attacks in September and October (HX72, SC7, HX79) achieved significant successes.

1941: Challenges and the Capture of Enigma The beginning of 1941 started well with a group consisting of U-69, U-73, U-95 and U-96 attacking Convoy OB288. However, this ‘Happy Time’ came to an end in March with the loss of three important aces: Prien, Schepke and Kretschmer. The Allies began installing radar on escort vessels and started using high-frequency signal detection equipment (Huff Duff) to detect U-boat signals. Most importantly, the Enigma machine and code books captured from U-110 on 9 May 1941 enabled British intelligence (Bletchley Park) to decipher German naval codes. This allowed the Allies to predict U-boat positions and steer their convoys away from danger. German fuel supply tankers were also ambushed and sunk thanks to the Enigma information obtained. However, 445 enemy ships were sunk during the year, but 38 U-boats were lost. The year ended with a total of 247 U-boats.

1942: The Second ‘Happy Time’ and the Caribbean Mission Japan's attack on Pearl Harbor and Germany's declaration of war on the United States directed U-boats towards American shores. This period, which began with Operation Paukenschlag (Drumbeat), was known as the ‘Second Happy Time’ due to the weakness of American anti-submarine defences. Between January and May 1942, 30 U-boats sank 360 enemy ships (approximately 2,250,000 tonnes) and lost only eight U-boats. With the US beginning to implement convoys, the Caribbean became a new primary target for U-boats. June-December 1942 saw one of the most successful U-boat campaigns, with 97 U-boats operating in the Caribbean and 17 lost. For every U-boat sunk in this campaign, an average of 23 Allied ships were lost. Operations such as Operation Neuland achieved great success in the region. However, logistical difficulties and increased Allied countermeasures reduced their success here by the end of 1942. U-Tankers (Milchkuh) were introduced, enabling U-boats to refuel during long-range operations. However, some, such as U-464, were lost in 1942. The Laconia Incident (September 1942) occurred when U-156 rescued both Italian prisoners of war and Allied civilians from a sunken ship. However, an attack by a US aircraft prompted Admiral Dönitz to issue the “Laconia Order”: ‘No attempt should be made to rescue the crews of sunken ships.’ This order was seen as a response to Allied aggression and the importance of U-boat safety. 1942 was a highly successful year, with 1,090 ships (approximately 5,819,000 tonnes) sunk, but 88 U-boats lost.

1943: Black May and Strategic Changes 1943 was a difficult year for U-boats. While 290 new boats were commissioned, 245 were lost, indicating that losses were approaching the rate of new construction. The loss of experienced crews was particularly worrying. The Allies' use of advanced radar (ASV III) and “Leigh Light” rendered surface U-Boats highly vulnerable to air attacks. The Metox receiver could detect the old 1.7m wavelength radar but could not detect the new 10cm radar. The “Naxos” system was developed to detect newer radars, but it had a very short range of 5-8 km. On 1 May 1943, the Ständiger Kriegsbefehl 483 order was issued, instructing U-boats to remain on the surface and engage in combat with maritime patrol aircraft. However, this resulted in the German Navy losing 26 more boats and 17 boats being seriously damaged in such engagements. May 1943 became known as ‘Black May’ and led to heavy losses in the Atlantic. Dönitz shifted his main focus back from the Atlantic to the Brazilian coast. However, even in this region, the loss of U-Tankers and increased air attacks restricted operations. Many U-Tankers were sunk, making it difficult for combat U-Boats to refuel. The idea of operating in the Far East (Monsoon Boats) was raised. A German naval base was established in Penang, and the first Monsoon boats set sail in mid-1943. However, many boats were lost during transport.

1944: Disaster The year 1944 was a ‘disaster’ for U-boats. While only 131 enemy ships were sunk, over 100 U-boats were lost. U-boat production could not keep pace with the losses. Wolf pack tactics against Atlantic convoys proved ineffective. Although the Normandy Landings in June 1944 presented major targets for U-boats, significant success was not achieved due to Allied air superiority and the heavy presence of escort vessels. Even Schnorchel-equipped boats struggled to evade air attacks. All remaining U-Tankers were also sunk, further reducing the U-Boats' resilience at sea. All 62 U-Boats in the Mediterranean were lost by the end of 1944. Operations in the Caribbean also decreased, with only a few sinkings recorded throughout the year. However, the Monsoon boats remained active in the Far East and achieved some successes. But reinforcement efforts here also resulted in the loss of many boats during transit.

1945: The Beginning of the End The final months of the war saw heavy losses for the U-boats. In the last major convoy battle of April 1945, RA66, a group of 14 U-boats managed to sink only one frigate. On 4 May 1945, Admiral Dönitz ordered his U-Boats to cease fire. In a second personal message, he stated that the U-Boat crews had fought ‘like lions’ and laid down their arms ‘unconquered and unsullied’. Between January and May 1945, 71 enemy ships were sunk, while nearly 400 U-boats were lost. By the end of the war, only 102 operational U-boats remained.

U-Boat Losses in World War II

Throughout World War II, a total of 805 U-Boats belonging to the German Navy (Kriegsmarine) were sunk. 663 of these losses were the result of enemy attacks. Enemy aircraft and warships were among the most significant causes of these losses.

Towards the end of the war, an operation called ‘Operation Regenbogen’ (Rainbow) was launched to prevent them from being captured by the enemy. As part of this operation, 219 of the 376 U-Boats that surrendered were deliberately sunk by their crews.

Overall, approximately 65% of the U-boats possessed by the Germans were lost during the war.

The Air Threat to U-boats in World War II: A Tactical and Technological Impasse

In the later stages of World War II, one of the greatest challenges to U-boat operations was Allied air superiority. While U-boats could operate effectively against enemy surface ships at the beginning of the war, the development and proliferation of air power completely changed the course of submarine warfare. U-boat commanders found themselves under constant deadly threat from the air, and this situation fundamentally affected operational tactics and technological developments. This section examines the threat posed by Allied aircraft to U-boats, the impact of this threat on U-boat losses, and the defensive measures developed by the German Navy in response.

The Rise of Allied Air Power and U-boat Losses

During World War II, Allied forces implemented a comprehensive air defence strategy to protect Atlantic convoys from the U-boat threat. This strategy encompassed various operational plans involving land-based aircraft, escort-class aircraft carrier-based elements (such as the USS Bogue and HMS Audacity), and amphibious seaplanes. The primary objective of these plans was to ensure the safety of Atlantic convoys and minimise the destruction caused by the U-boat threat.

Air Support in the Battle of the Atlantic: Closing the Land Gap

At the beginning of the Second World War, there was a critical 800-kilometre gap in the middle of the Atlantic Ocean where land-based aircraft were unable to reach. This area was commonly known as the ‘Black Hole’ and, due to the lack of sufficient escort-class aircraft carriers, provided U-boats with almost unlimited freedom of movement.

The Atlantic convoys, which formed the overseas logistical line of the Second World War, required vital defence against the German U-boat threat. In this context, the systematic and multi-layered deployment of Allied air power created a significant turning point that changed the course of the war.

The increase in the number of bases around the Atlantic and the introduction of escort-class aircraft carriers expanded the Allies' airspace. Escort-class aircraft carriers, such as the USS Bogue (CVE-9), in particular, provided constant air cover for convoys, limiting the U-boats' ability to surface and attack.

Modified long-range B-24 Liberator aircraft closed the previously air-defence-deficient ‘mid-Atlantic gap,’ enabling operations in the convoy's most vulnerable area. These aircraft demonstrated high success in both reconnaissance and attack missions.

On the other side of the Atlantic, the RAF Coastal Command was initially limited to short-range Avro Anson and Sunderland seaplanes in 1939. However, by 1942, with the introduction of the Liberator into service, the range and effectiveness of air operations increased significantly. This transition was a critical step in establishing a force structure appropriate to the threat environment.

In naval assets, the Naval Air Force, operating with inadequate equipment at the start of the war, rapidly increased its operational capacity with the introduction of escort-class aircraft carriers. These platforms, converted from commercial vessels or purpose-built, enabled air-sea coordination.

By mid-1943, coordinated operations by Allied air and naval forces from both sides of the Atlantic had brought the Atlantic region, known as the “Black Hole” and long deprived of air support, completely under control. This critical development made it possible to provide uninterrupted air cover for convoys, significantly reducing the operational effectiveness of German U-boats.

Target: U-Boats - The Striking Weapons of the Allied Air Force

Depth Charges: These were the most common weapon dropped from aircraft when U-Boats were detected underwater. Set to explode at a specified depth, they inflicted serious damage on submarines with the shock wave they created.

Rockets: Rockets integrated into aircraft in the later years of the war became highly effective against U-boats. Aircraft such as the British Beaufighter and Mosquito, equipped with these weapons, were capable of fast and direct attacks.

Torpedoes: Some Allied aircraft, particularly the American Grumman TBF Avenger, had the capability to carry torpedoes.

These weapons were generally used against U-boats on the surface. Machine Gun and Gun Fire: When U-boats surfaced, they were targeted directly by aircraft with machine gun and gun fire. The periscope, the submarine's conning tower, and the crew were particularly high-priority targets in these attacks.

A hole in the hull during an attack could render the U-boat unusable.

Radar and Sonar-Assisted Targeting Systems: To increase the effectiveness of their munitions, aircraft were equipped with advanced systems such as radar and magnetic anomaly detectors. These technologies detected the location of U-boats underwater, increasing the accuracy of attacks.

The Allies' intelligent use of various types of munitions significantly reduced the impact of the U-boat threat.

As the war progressed, the use of aircraft in Allied anti-submarine operations increased exponentially. It quickly became apparent that the single 2 cm anti-aircraft gun found on the first U-boats was woefully inadequate against this threat. Sources indicate that a large proportion of U-boat losses were the result of enemy aircraft or warship attacks. Of the total 805 U-boat losses, 663 were attributed to enemy action. U-boat commanders avoided engaging aircraft unless absolutely necessary, instead adopting a tactic of diving to evade.

Significant U-Boat Losses and Air Attacks

Allied air attacks had devastating consequences for the German Navy during critical periods of the war. Some notable examples include:

● U-26: Sunk by depth charges from a Sunderland aircraft on 20 June 1940.

● U-109: Bombarded by Allied aircraft near the Azores on 4 May 1943.

● U-464 (Type XIV U-tanker): Sunk on the surface by an Allied bomber on 20 August 1942.

● July 1943 Losses: Four U-tankers (U-459, U-461, U-462, U-487) were hunted down and sunk on the surface by Allied aircraft within a month.

● U-460: On 4 October 1943, it was detected on the surface while refuelling alongside other U-boats and destroyed.

● U-489: On 22 July 1943, it sustained heavy damage during an aircraft attack while recharging its batteries and was abandoned.

● U-615 (Type VIIC): In August 1943, despite heavy anti-aircraft fire, it was subjected to successive air attacks and eventually sank.

● Base Attacks: The U-boat shelter at Brest suffered extensive damage during the ‘Tallboy’ air raids in August 1944, and some U-boats, such as U-24, were sunk at their bases.

Defensive Measures Developed Against the Aircraft Threat

The German Navy attempted to develop various tactical and technological innovations to counter the increasing air threat.

Enhancement of Anti-Aircraft Weapons:

To counter the air threat, U-Boats were equipped with more powerful weapons such as twin 2 cm machine guns, four-barrelled 2 cm ‘Flakvierling’ or single 3.7 cm flak guns. Even heavily armed U-boats called ‘Flak Boats’ were tested, but the project was cancelled because this heavy armament negatively affected dive times.

Radar Detection and Countermeasures:

U-boats began using the FuMB1 “Metox” receiver to detect enemy radar signals. However, it was discovered that Metox's own signals were being detected by Allied radars. Consequently, the ‘Naxos’ system was developed, capable of detecting stronger radar signals, but this system also had a very limited range.

‘Leigh Light’ and “Aphrodite”:

The Allies were able to easily illuminate and attack U-boats on the surface using the radar-guided ‘Leigh Light’ spotlight, while the Germans attempted to counter this with radar deception devices such as ‘Aphrodite’.

Schnorchel:

The Schnorchel device, fitted to U-boats in 1944, eliminated the need for submarines to surface to recharge their batteries. While this technology made U-boats safer against air attacks, it also had its own problems, such as noise and ventilation issues.

Alberich (Sound Insulation):

The synthetic rubber coating ‘Alberich’, which was planned to be applied to the U-boat hull, aimed to reduce Allied sonar effectiveness but failed due to the inability to find a suitable adhesive.

Tactical Changes and the ‘Fight Enemy Aircraft’ Order

As the aircraft threat increased, U-boat hunting tactics also changed; the practice of finishing off target ships with gunfire was gradually abandoned. In May 1943, during a period known as ‘Black May,’ German Navy Commander Dönitz ordered U-boats to remain on the surface and engage in combat during air attacks. However, this order resulted in the loss of 26 vessels and severe damage to 17 others within approximately three months. This tactical shift left U-boats vulnerable to attack at their most exposed moments and ultimately failed because the Allies could replenish their air power far more easily against the U-boats.

The information provided clearly demonstrates that throughout the Second World War, Allied aircraft became an increasingly significant and ultimately catastrophic threat to U-boats. The German Navy's attempts to counter this threat, both tactically and technologically, reveal how air superiority determined the fate of submarine warfare. The effectiveness of U-boats at the start of the war was seriously compromised by the development of Allied air power and technology.

Post-War: Operation Deadlight

Following Germany's surrender in May 1945, approximately 150 operational U-boats remained. These were captured by the Allies for examination. Some U-boats entered service in Allied navies (for example, U-995 served in the Danish Navy as Kaura). However, there was no further use for the majority of the captured U-boats. In an operation called Operation Deadlight, these boats were towed out to deep waters and sunk, or used for target practice. A total of 115 U-boats were sunk during this operation, with the last one sunk on 12 February 1946.

Conclusion

German U-boats achieved significant successes in the early years of World War II, particularly during the “Wolf Pack” tactics and when Allied anti-submarine defences were weak. The “First” and “Second Happy Times” and the campaigns in the Caribbean stood out for their large tonnage sinkings. However, Allied technological advances (radar, “high-frequency signal detection equipment” / “Huff Duff”), intelligence successes (the breaking of Enigma) and improved convoy defences meant that U-boats began to suffer serious losses. “Black May” in 1943 marked a turning point in the U-boat war in the Atlantic. In subsequent years, despite innovations such as the Schnorchel and improved torpedoes, the operational capabilities and successes of U-boats declined significantly, while U-boat losses steadily increased. It is estimated that approximately 30,000 U-boat personnel lost their lives during the Second World War. At the U-boat memorial in Möltenort, there are bronze panels inscribed with the names of every U-boat sailor who died on duty during the Second World War. These panels list the names of 28,748 sailors.

The loss rate was particularly high among those serving on frontline operational boats. Of the approximately 30,000 U-boat personnel who lost their lives, approximately 22,000 (73%) were serving on Type VII submarines.

By the end of the war, despite the heroic efforts of U-boat personnel, the overwhelming Allied material supply superiority and the advanced countermeasures developed by the Allies against U-boats ended Germany's submarine warfare. This article summarises this vital struggle that influenced the course of the war.

For readers wishing to gain a deeper understanding of the operational dynamics of the Battle of the Atlantic and the human impact of naval warfare, two films offer a special viewing experience. Greyhound, starring Tom Hanks and released in 2020, depicts Allied convoy defence tactics in a fast-paced narrative, while Wolfgang Petersen's 1981 masterpiece Das Boot strikingly and realistically portrays the psychological struggle of a German submarine crew in a claustrophobic atmosphere. Both films present the multi-layered nature of the Battle of the Atlantic to the viewer in both its technical and human dimensions.

References

U-boat Types - German U-boats of WWII - Kriegsmarine - uboat.net

https://uboat.net/allies/aircraft/avenger.htm

Battle of the Atlantic - Wikipedia

https://www.historyhit.com/facts-about-the-battle-of-the-atlantic-in-world-war-two/

https://www.history.navy.mil/about-us/leadership/director/directors-corner/h-grams/h-gram-019/h-019-4.html

Jak Mallmann Showell ‘’Wolfpacks at War: The U Boat Experience in World War II’’

Gordon Williamson ‘’WOLF PACK The Story of the U-Boat in World War II’’