Type XXI U-boat

Type XXI U-boat was the revolutionary German submarine of the Second World War, known as the Elektroboot, the first submarine designed to operate mainly submerged, rather than as a surface ship that could dive. Built in 118 boats between 1944 and 1945, the Type XXI could travel faster submerged, at about 17.2 knots, than on the surface, at about 15.6 knots, and it could stay submerged for days, charging its batteries with a snorkel and attacking with a new, fast-reloading torpedo system. The boat was a radical break from the Type VII and Type IX, which had been designed in the 1930s, and it influenced submarine design for decades after the war, in the Soviet, American, British, and French navies. The Type XXI came too late to change the outcome of the war: only two boats made war patrols, neither sank a ship, and most of the boats were scuttled or captured at the end of the war. The boat’s importance lies not in what it did in the war, but in what it showed about the future of the submarine.

1. Key Facts

Class/Type	Type XXI Elektroboot
Launched	First boat, U-2501, launched 1944
Commissioned	1944-1945
Displacement	About 1,621 tons surfaced; about 1,819 tons submerged
Length	76.7 metres
Speed	About 15.6 knots surfaced; about 17.2 knots submerged
Complement	57 officers and men
Armament	6 torpedo tubes (all bow); 23 torpedoes; 2 x 20 mm anti-aircraft guns
Aircraft	None
Fate	118 built; 2 war patrols; most scuttled or captured; U-2540 preserved

2. Development

The Crisis of 1943

The Type XXI was born from the crisis of 1943, when the U-boat war was lost. In May 1943, known as Black May, the Allies sank 43 U-boats in a single month, and Admiral Karl Donitz withdrew his boats from the Atlantic. The Type VII and Type IX, which had been designed as surface ships that could submerge, were vulnerable to aircraft, radar, and escort carriers, and they could not operate in the Atlantic without being found and sunk. The German navy needed a new submarine, one that could stay submerged, outrun escorts, and attack without surfacing, and the Type XXI was the answer. The design was drawn up in 1943, based on the work of the naval engineer Hellmuth Walter, who had designed a submarine with a high-speed, streamlined hull and a large battery, and on the experience of the U-boat war. The first boat, U-2501, was laid down in 1944, and production was organised in sections, built in different yards and assembled in others, to speed construction and to avoid bombing.

Production in Sections

The Type XXI was built in sections, a new method for German shipbuilding, in which the hull was divided into eight prefabricated sections, built in inland yards and transported to assembly yards on the coast. The method was intended to speed production and to use yards that had never built submarines, but it caused problems: the sections were built to different tolerances, and they often did not fit together, causing delays and leaks. The production was also disrupted by Allied bombing, which damaged yards and destroyed sections, and by the shortage of steel, labour, and equipment. Despite these problems, 118 Type XXI boats were completed between 1944 and 1945, and more were under construction at the end of the war. The boats were built quickly, in about six months, but many were incomplete when they were commissioned, and they needed months of work to make them ready for sea. Only a handful were ever operational, and only two made war patrols.

3. Design

A Streamlined Hull

The Type XXI hull was 76.7 metres long, 8 metres wide, and about 1,621 tons surfaced, rising to about 1,819 tons submerged. The hull was streamlined, with a smooth, teardrop shape, a small conning tower, and no deck gun, which reduced drag and let the boat travel faster submerged than on the surface. The design was a break from the Type VII and Type IX, which had a flat deck, a large conning tower, and a deck gun, and which were designed for surface operations. The Type XXI’s hull was designed for submerged speed, with a large battery that gave it a submerged range of about 340 nautical miles at 5 knots, and a submerged speed of about 17.2 knots for short periods. The boat could stay submerged for days, using its snorkel to run its diesels and charge its batteries, and it could attack without surfacing, using its sonar to find targets and its torpedoes to sink them.

The Battery and the Snorkel

The Type XXI’s battery was three times larger than that of the Type VII, with 372 cells, and it gave the boat a submerged endurance that was far greater than any earlier submarine. The battery could be charged by the diesels, using the snorkel, a breathing tube that let the diesels run while the boat was submerged at periscope depth, and it could power the boat for days without surfacing. The snorkel was a key part of the design, because it let the boat stay submerged and avoid aircraft, although it could be detected by radar, and it limited the boat’s speed and depth. The boat’s machinery was also new: two diesel engines, producing about 4,000 horsepower, and two electric motors, producing about 5,000 horsepower, which drove two shafts. The electric motors were more powerful than the diesels, a reversal of the usual arrangement, and they gave the boat its high submerged speed. The boat’s design was a revolution, and it set the pattern for post-war submarines.

4. Technical Specifications

Dimensions and Performance

The Type XXI measured 76.7 metres in length, 8 metres in beam, and 6.3 metres in draught. Her surfaced displacement was about 1,621 tons, and her submerged displacement was about 1,819 tons. Her surface speed was about 15.6 knots, and her submerged speed was about 17.2 knots, faster submerged than on the surface, a first for a submarine. Her range was about 15,500 nautical miles at 10 knots on the surface, and about 340 nautical miles at 5 knots submerged. Her test depth was about 280 metres, deeper than the Type VII, and her complement was 57 officers and men, including the commander, officers, petty officers, and ratings. The boat carried 23 torpedoes, all in the bow, and its fuel capacity was about 250 tons. The figures vary between sources because the boats were built in sections and modified during production, and because many were incomplete when they were commissioned.

Sensors and Equipment

The Type XXI carried the most advanced sensors of any German submarine: a passive sonar, the Gruppenhorchgerat, for listening, and an active sonar, the Nibelung, for ranging, which let the boat find and attack targets without using its periscope. The boat also carried a radar detector, the Metox, and a radar set, the FuMO 65, for surface search, although the radar was rarely used, because it gave away the boat’s position. The boat’s periscopes were the attack periscope, for torpedo aiming, and the observation periscope, for general observation, although the boat was designed to attack using sonar alone, without raising a periscope. The boat’s torpedo fire control was by a computer, which calculated the firing solution from the sonar data, and it could fire torpedoes in a spread, reload in minutes, and fire again. The boat’s equipment was a major advance, and it influenced post-war submarine design, although it was never fully tested in combat.

5. Armament

Torpedoes and the Fast Reload

The Type XXI carried six torpedo tubes, all in the bow, and 23 torpedoes. The torpedoes were carried in the bow torpedo room, and in a new, fast-reloading system that used a hydraulic ram to load torpedoes in minutes, rather than the 20 minutes it took on the Type VII. The system let the boat fire a spread of six torpedoes, reload, and fire again in less than 10 minutes, a rate of fire that was far higher than any earlier submarine. The torpedoes were the standard G7e electric type, with a range of about 5,000 metres at 30 knots, and the acoustic torpedo, the Zaunkonig, which homed on the noise of a ship’s propellers. The boat had no stern torpedo tubes, because the design prioritised the bow attack, and it had no deck gun, because the boat was designed to stay submerged and to avoid surface action. The boat’s armament was designed for submerged attack, and it was the most effective torpedo armament of any submarine of the war.

Anti-Aircraft Guns

For air defence, the Type XXI carried two 20 mm anti-aircraft guns, mounted on the conning tower platform, although the guns were a last resort, because the boat was designed to stay submerged and to avoid aircraft. The guns were rarely used, and they were removed from some boats to save weight and to reduce drag. The boat’s main defence was its ability to stay submerged, to outrun escorts, and to avoid detection, and its anti-aircraft guns were kept only for emergencies. The boat’s design reflected the lesson of the U-boat war: a submarine that fought an aircraft on the surface was likely to be sunk, and the only safe submarine was a submerged submarine. The Type XXI’s anti-aircraft armament was minimal, because the boat was not expected to fight on the surface, and its survival depended on its submerged speed and its sonar, not on its guns.

6. Service History

Two War Patrols

The Type XXI made only two war patrols, and neither sank a ship. U-2511, under Adalbert Schnee, sailed on 30 April 1945, and on 4 May 1945, she encountered a British cruiser group, and Schnee, using his sonar, manoeuvred into attack position without being detected, and simulated an attack on the cruiser Norfolk, before withdrawing on orders when the war ended. U-3008, under Helmut Manseck, sailed on 3 May 1945, and she also made no attack before the war ended. The two patrols showed that the Type XXI could operate submerged, evade escorts, and attack without being detected, but they came too late to affect the war. The boats that were commissioned in 1944 and 1945 spent most of their time in trials, training, and repairs, and many were never operational. The Type XXI’s service history is a history of promise unfulfilled, of a boat that was built too late, in too few numbers, and with too little time to learn to use it.

The End of the War

At the end of the war, most Type XXI boats were scuttled by their crews, to keep them from falling into Allied hands, or surrendered to the Allies. About 84 boats were scuttled in May 1945, in Operation Regenbogen, and the remainder were handed over to the Allies, who divided them among themselves for study. The boats were studied by the American, British, Soviet, and French navies, and they influenced the design of post-war submarines in all four countries. The American navy built the Tang class, based on the Type XXI, and the Soviet navy built the Whiskey class, also based on the Type XXI, and the British and French navies built submarines that drew on the Type XXI’s design. The Type XXI’s service history ended with the war, but its influence continued for decades, in the submarines that were built after it.

7. Notable Actions

U-2511 and the Simulated Attack

U-2511, under Adalbert Schnee, is the most famous Type XXI because she made the only war patrol that came close to an attack. On 4 May 1945, Schnee, using his sonar, detected a British cruiser group, including the cruiser Norfolk, and he manoeuvred U-2511 into attack position, without being detected by the British escorts, and simulated a torpedo attack on Norfolk, before withdrawing on orders when the ceasefire was announced. The simulated attack showed that the Type XXI could approach a warship group, undetected, and attack, a feat that the Type VII could not have achieved, because it would have been detected on the surface or by sonar. Schnee’s patrol is often cited as proof that the Type XXI would have been a formidable weapon if it had been available earlier, and it is the only evidence of the boat’s capabilities in combat conditions. U-2511 was surrendered to Britain after the war and sunk as a target in 1946.

U-2540 and Wilhelm Bauer

U-2540, a Type XXI, is the most famous surviving boat, because she was raised after the war, served in the German navy as Wilhelm Bauer, and is now preserved as a museum ship at Bremerhaven, Germany. U-2540 was scuttled in May 1945, raised in 1957, and commissioned into the West German navy as Wilhelm Bauer in 1960, where she served as a research submarine until 1982. She was then preserved as a museum, and she is now the only surviving Type XXI, and the only place where visitors can see the interior of the Elektroboot. The boat’s preservation is a tribute to the Type XXI’s design, and to the engineers who built it, and it is visited by thousands of people each year. U-2540’s story, from scuttling to museum, is the story of the Type XXI itself: a boat that was built for war, but that found its purpose in peace, as a museum and a research vessel.

8. Fate

Scuttled and Captured

Most Type XXI boats were scuttled or captured at the end of the war. Of the 118 boats built, about 84 were scuttled in May 1945, in Operation Regenbogen, and the remainder were surrendered to the Allies. The boats that were surrendered were divided among the Allies: the Americans took U-2513 and U-3008, the British took U-2502 and others, the Soviets took U-3515 and others, and the French took U-2518, which served as Roland Morillot until 1967. The boats were studied, tested, and in some cases, put into service, and they influenced the design of post-war submarines in all four countries. The boats that were scuttled were raised after the war and scrapped, and the wrecks that remain are war graves. The Type XXI’s fate was to be built too late, to be scuttled or captured, and to be studied, rather than to fight, and its story is a reminder of the limits of technology when it comes too late.

Survivors and Preservation

Only one Type XXI survives: U-2540, preserved as Wilhelm Bauer at Bremerhaven, Germany. The boat was scuttled in 1945, raised in 1957, and served in the West German navy until 1982, before being preserved as a museum. She is the only surviving Elektroboot, and she is the only place where visitors can see the interior of the boat that revolutionised submarine design. Other Type XXI boats were preserved for a time, but they were scrapped or sunk as targets, and U-2540 is the last. The boat’s preservation is a tribute to the Type XXI’s design, and to the engineers who built it, and it is visited by thousands of people each year. The Type XXI’s legacy is preserved in U-2540, in the submarines that were built after it, and in the records of the U-boat war, which show the boat as the future of the submarine, built too late to change the past.

9. Legacy

The Submarine of the Future

The Type XXI was the submarine of the future, and it shaped submarine design for decades after the war. Its streamlined hull, large battery, snorkel, and fast-reloading torpedo system were adopted by the American, Soviet, British, and French navies, and they became the standard for post-war submarines. The American Tang class, built in the late 1940s, was based on the Type XXI, and the Soviet Whiskey class, built in the 1950s, was also based on the Type XXI, with more than 200 boats built. The British and French navies built submarines that drew on the Type XXI’s design, and the boat’s influence can be seen in the submarines that were built in the 1950s and 1960s, including the first nuclear submarines, which used the Type XXI’s hull form. The Type XXI showed that a submarine could be faster submerged than on the surface, and that it could stay submerged for days, and those ideas became the foundation of modern submarine design.

Memory and the Elektroboot

The Type XXI is remembered as the Elektroboot, the revolutionary submarine that came too late, and as the boat that shaped the future of submarine warfare. The boat is remembered in the museum ship U-2540, at Bremerhaven, and in the histories of the U-boat war, which cite it as the weapon that could have changed the Battle of the Atlantic if it had been available in 1943. The boat’s story is a cautionary tale for any navy that seeks to build a revolutionary weapon: it must be built in time, in sufficient numbers, and with the training to use it, or it will be a museum piece, not a weapon. For historians, the Type XXI stands as an example of a weapon that was superbly designed for the war it was intended for, and that became obsolete when the war ended, a pattern that has repeated in naval warfare ever since.

10. Frequently Asked Questions

What was the Type XXI U-boat?

The Type XXI was a German revolutionary submarine of the Second World War, known as the Elektroboot, the first submarine designed to operate mainly submerged. It was a radical break from the Type VII and Type IX, which had been designed in the 1930s as surface ships that could dive. Built in 118 boats between 1944 and 1945, it could travel faster submerged, at about 17.2 knots, than on the surface, at about 15.6 knots. It could stay submerged for days, charging its batteries with a snorkel and attacking with a new, fast-reloading torpedo system.

How many Type XXI U-boats were built?

118 Type XXI boats were built between 1944 and 1945, but only two made war patrols, and neither sank a ship. The war ended before the boats could be used in numbers, and most of the boats were scuttled or captured at the end of the war. The Type XXI came too late to change the outcome of the war, and its importance lies not in what it did in the war, but in what it showed about the future of the submarine. The first boat, U-2501, was launched in 1944, and the boat influenced submarine design for decades after the war.

How fast was the Type XXI submerged?

The Type XXI could travel at about 17.2 knots submerged, faster than its surface speed of about 15.6 knots, a first for a submarine. It could stay submerged for days, using its snorkel to charge its batteries, and it was the first submarine designed to operate mainly submerged. Its large electric battery gave it its high submerged speed and endurance, and it was powered mainly by that battery, which is why it was called the Elektroboot. The boat was 76.7 metres long, displaced about 1,621 tons surfaced and about 1,819 tons submerged, and carried a crew of 57 officers and men.

What was the Elektroboot?

Elektroboot, meaning electric boat, was the German name for the Type XXI, because it was powered mainly by its large electric battery. That battery gave it its high submerged speed and endurance, and the Type XXI could travel at about 17.2 knots submerged, faster than on the surface. The boat could stay submerged for days, charging its batteries with a snorkel, and it was the first submarine designed to operate mainly submerged. It was a revolutionary German submarine of the Second World War, built in 118 boats between 1944 and 1945, and it influenced submarine design for decades.

Where can I see a Type XXI today?

U-2540, a Type XXI, is preserved as the museum ship Wilhelm Bauer at Bremerhaven, Germany, and she is the only surviving Type XXI. 118 Type XXI boats were built between 1944 and 1945, and most were scuttled or captured at the end of the war, so only one survives. Only two boats made war patrols, and neither sank a ship, because the war ended before the boats could be used in numbers. The Type XXI was the revolutionary Elektroboot, the first submarine designed to operate mainly submerged, and U-2540 is its last survivor.

How did the Type XXI influence post-war submarines?

The Type XXI influenced the American Tang class, the Soviet Whiskey class, and British and French submarines after the war. Its streamlined hull, large battery and snorkel became the standard for post-war submarine design, and navies studied the boat after the war. The boat was a radical break from the Type VII and Type IX, which had been designed in the 1930s, and it showed the future of the submarine. It could travel faster submerged, at about 17.2 knots, than on the surface, at about 15.6 knots, and it could stay submerged for days.

11. Sources

1. Wikipedia, “German Type XXI submarine” — development, specifications, and service.
2. Clay Blair, “Hitler’s U-Boat War: The Hunted, 1942-1945” (Random House, 1998) — the Type XXI and the end of the U-boat war.
3. Erich Groner, “German Warships 1815-1945, Vol. 2: U-boats and Mine Warfare Vessels” (Conway, 1991) — specifications and production data.
4. Uboat.net, “Type XXI” — boat lists, patrols, and losses.
5. Eberhard Rossler, “The U-boat: The Evolution and Technical History of German Submarines” (Cassell, 1981) — design and development.
6. German Maritime Museum, Bremerhaven, “Wilhelm Bauer (U-2540)” — the preservation of U-2540.