Type VII U-boat

Type VII U-boat was the standard submarine of the German Kriegsmarine in the Second World War, and the most numerous submarine type ever built. About 703 Type VII boats were completed between 1936 and 1945, in the variants VIIA, VIIB, VIIC, VIIC/41, VIID, and VIIF, and they formed the backbone of the U-boat war in the Atlantic. The Type VII was a medium-sized, ocean-going boat, designed for operations in the North Sea and the western Atlantic, with a range of about 6,500 nautical miles on the surface and a crew of about 44 to 52 men. It was fast enough to keep up with a convoy on the surface, quiet enough to evade escorts when submerged, and armed with five torpedo tubes and a deck gun. The Type VII sank more Allied shipping than any other submarine type in history, but it also suffered the heaviest losses: about 80 per cent of the boats were lost, and about 30,000 German submariners died, most of them in Type VII boats. The story of the Type VII is the story of the Battle of the Atlantic itself.

1. Key Facts

Class/Type	Type VII U-boat (variants VIIA, VIIB, VIIC, VIIC/41, VIID, VIIF)
Launched	First boat, U-27, launched 1936
Commissioned	1936-1945
Displacement	About 626 tons surfaced and 745 tons submerged (VIIA); about 769 tons surfaced and 871 tons submerged (VIIC)
Length	64.5 metres (VIIA); 67.1 metres (VIIC)
Speed	About 17.7 knots surfaced; about 7.6 knots submerged (VIIC)
Complement	44-52 officers and men
Armament	5 torpedo tubes (4 bow, 1 stern); 11-14 torpedoes; 1 x 88 mm deck gun; 1 x 20 mm anti-aircraft gun
Aircraft	None
Fate	About 703 built; about 80 per cent lost; a few preserved

2. Development

From the Type I to the Type VII

The Type VII was developed from the Type I, a large ocean-going boat of which only two were built in the mid-1930s. The German navy needed a smaller, cheaper boat that could be built in large numbers, and the Type VII was the answer: a medium boat that could operate in the Atlantic, dive quickly, and carry enough torpedoes to sink a convoy. The design was based on the Finnish submarine Vesikko, which had been built in Germany in secret during the 1930s, when Germany was forbidden to build submarines under the Treaty of Versailles. The first Type VII, U-27, was laid down in 1935 and commissioned in 1936, and production continued through the war, with boats built at shipyards in Kiel, Hamburg, Bremen, and Danzig. The Type VII was the boat that Admiral Karl Donitz, commander of the U-boat force, built his wolfpack tactics around, and it was the boat that carried the U-boat war to its height in 1942 and to its defeat in 1943.

The Variants of the Family

The Type VII family grew through the war, as the navy added fuel, torpedoes, and equipment. The VIIA, 10 boats, was the original design, with a displacement of about 626 tons surfaced and 11 torpedoes. The VIIB, 24 boats, was longer, with more fuel and a longer range, and it carried 14 torpedoes. The VIIC, 568 boats, was the main wartime variant, with a slightly larger hull, more fuel, and 14 torpedoes, and it is treated in a separate article because it was the most numerous submarine class in history. The VIIC/41, 91 boats, had a stronger pressure hull and a deeper test depth. The VIID, 6 boats, was a minelaying variant, with five mine shafts behind the conning tower, and the VIIF, 4 boats, was a torpedo supply boat, which carried spare torpedoes for other U-boats at sea. In total, about 703 Type VII boats were built, more than any other submarine type, and the family as a whole sank about 14 million tons of Allied shipping.

3. Design

Hull and Layout

The Type VII was a single-hulled boat, with a pressure hull that carried the crew and machinery, and saddle tanks on the sides that carried fuel and ballast. The pressure hull was divided into six compartments: the bow torpedo room, the forward crew quarters, the control room, the officers’ quarters, the engine room, and the stern torpedo room. The boat was cramped, with the crew living in bunks that were shared in shifts, and with little space for stores or fresh water. The conning tower, with its bridge and periscopes, was the centre of the boat in action, and the commander directed attacks from the tower, using the periscope to aim torpedoes. The boat’s design was a compromise: it was small enough to be built quickly and cheaply, large enough to operate in the Atlantic, and fast enough to keep up with a convoy, but it was not comfortable, and its range was limited compared with the larger Type IX.

Machinery and Diving

The Type VII was powered on the surface by two diesel engines, producing about 2,800 to 3,200 horsepower, and submerged by two electric motors, producing about 750 horsepower. Her surface speed was about 17 to 17.7 knots, and her submerged speed was about 7.6 knots, although she could only maintain that speed for a short time before her batteries were exhausted. Her range was about 6,500 nautical miles at 12 knots on the surface, and about 80 nautical miles at 4 knots submerged. The boat could dive in about 25 seconds, faster than the larger Type IX, and that speed was a matter of life and death when aircraft appeared. Her test depth was about 220 metres, although boats were often driven deeper in emergencies, and the VIIC/41, with its stronger hull, could dive to about 250 metres. The boat’s sonar and hydrophones were standard for the period, and its periscopes were the attack periscope, for torpedo aiming, and the observation periscope, for general observation.

4. Technical Specifications

Dimensions and Performance

The Type VIIC, the representative variant of the family, measured 67.1 metres in length, 6.2 metres in beam, and 4.7 metres in draught. Her surfaced displacement was about 769 tons, and her submerged displacement was about 871 tons. Her surface speed was about 17.7 knots, and her submerged speed was about 7.6 knots. Her range was about 8,500 nautical miles at 10 knots on the surface, and about 80 nautical miles at 4 knots submerged. Her complement was 44 to 52 officers and men, including the commander, officers, petty officers, and ratings. The boat carried 14 torpedoes, or 26 mines in place of torpedoes, and its fuel capacity was about 114 tons. The earlier VIIA was smaller, at 64.5 metres and 626 tons surfaced, with a range of about 6,200 nautical miles, and the VIIB was intermediate, at 66.5 metres and 753 tons surfaced. The figures vary between sources because the boats were modified during production, and because displacement was calculated under different loading conditions.

Sensors and Equipment

The Type VII carried the standard German submarine sensors of the period: a Gruppenhorchgerat, a group listening device, for passive sonar, and an active sonar set for ranging. Its periscopes were the attack periscope, for torpedo aiming, and the observation periscope, for general observation. Its radio equipment included a transmitter and receiver for long-range communication with headquarters, and a radar detector, the Metox, which warned of Allied radar. Later in the war, boats were fitted with a snorkel, a breathing tube that let the diesels run while submerged at periscope depth, and with a radar set, the FuMO 29, for surface search. The boat’s torpedo fire control was manual, with the commander calculating the firing solution from the periscope, and the torpedoes were the standard G7a steam and G7e electric types, with a range of about 5,000 metres at high speed. The boat’s equipment was improved through the war, but it never matched the radar and sonar of the Allied escorts.

5. Armament

Torpedoes and Deck Gun

The Type VII carried five torpedo tubes, four in the bow and one in the stern, and 11 to 14 torpedoes, depending on the variant. The torpedoes were the main weapon, and the boat could fire a spread of four from the bow, reload, and fire again. The stern tube was used for a parting shot at a pursuing escort, or for attacking a ship behind the boat. The boat also carried an 88 mm deck gun, mounted forward of the conning tower, which was used to sink small ships and to finish off damaged ships, saving torpedoes for larger targets. The deck gun was effective in the early war, when Allied ships were unarmed, but by 1942 most merchant ships carried guns of their own, and the deck gun became too dangerous to use. The boat also carried mines, which could be laid from the torpedo tubes, and it was used for minelaying off British ports. Later in the war, the deck gun was removed from many boats to save weight and to reduce drag, and the boats relied on torpedoes alone.

Anti-Aircraft Guns

For air defence, the Type VII carried a 20 mm anti-aircraft gun, mounted on the conning tower platform, and later in the war, a second 20 mm gun and a 37 mm gun. The guns were a last resort, because a submarine that fought an aircraft on the surface was likely to be sunk, and the standard tactic was to dive. In 1943, the German navy tried a new tactic, fitting some boats with heavy anti-aircraft armament and ordering them to stay on the surface and fight, but the tactic failed: Allied aircraft were too numerous and too well armed, and boats that stayed on the surface to fight were sunk. The anti-aircraft guns were more useful against single aircraft in the early war, and they were sometimes used to shoot down patrol aircraft that had found the boat. By 1944, most Type VII boats had their deck guns removed and relied on the snorkel and on diving to escape, and the anti-aircraft guns were kept only for emergencies.

6. Service History

The Happy Time

The Type VII’s service history is the history of the U-boat war. In the first year of the war, the Type VII boats sank large numbers of Allied ships, often operating alone, off the British coast and in the western Atlantic. The period from July 1940 to early 1941, known as the Happy Time, was the high point of the U-boat war, when the Type VII boats, commanded by aces such as Gunther Prien, Otto Kretschmer, and Joachim Schepke, sank hundreds of thousands of tons of shipping. Prien’s U-47 sank the battleship Royal Oak at Scapa Flow in October 1939, a feat that made him a hero in Germany, and Kretschmer’s U-99 sank 44 ships in a few months, using the tactic of attacking on the surface at night, inside the convoy. The Happy Time ended when the British introduced convoys, escort groups, and radar, and the U-boat losses began to mount.

Wolfpacks and the Battle of the Atlantic

From 1941 onwards, the Type VII boats operated in wolfpacks, groups of 10 to 20 boats that were directed by radio to a convoy and attacked together, at night, on the surface. The wolfpack tactic was the brainchild of Admiral Donitz, and it was devastating in 1942, when the Type VII boats sank more than 6 million tons of Allied shipping, the highest total of the war. The boats operated from bases in France, at Brest, Lorient, and Saint-Nazaire, which gave them direct access to the Atlantic, and they were supported by supply boats, the Milchkuhe, which refuelled and rearmed them at sea. The wolfpack tactic reached its peak in early 1943, when the convoys were hard-pressed, but in May 1943, known as Black May, the Allies sank 43 U-boats in a single month, and Donitz withdrew his boats from the Atlantic. The Type VII never recovered its advantage, and the rest of the war was a losing battle.

7. Notable Actions

U-47 and the Royal Oak

U-47, a Type VIIB under Gunther Prien, carried out one of the most famous U-boat attacks of the war. On the night of 13-14 October 1939, Prien took U-47 into Scapa Flow, the main base of the British Home Fleet, through a gap in the defences that he had studied from photographs. Inside the anchorage, he found the battleship Royal Oak at anchor, and he fired torpedoes that sank her, killing 833 of her crew. Prien escaped through the same gap, and returned to Germany a hero, where he was awarded the Knight’s Cross and feted by Hitler. The attack was a propaganda triumph for Germany, and a shock to Britain, which had believed Scapa Flow was impregnable. Prien was killed in March 1941, when U-47 was sunk by the destroyer HMS Wolverine, but his attack on the Royal Oak remains the most famous single action by a Type VII boat.

U-99 and Otto Kretschmer

U-99, a Type VIIB under Otto Kretschmer, was the most successful U-boat of the war in terms of tonnage sunk. Kretschmer, who was known as Silent Otto because he rarely used his radio, sank 44 ships totalling about 266,000 tons in eight patrols, using the tactic of attacking on the surface at night, inside the convoy, where the escorts could not see him. Kretschmer’s tactic was to fire a single torpedo at each ship, to save torpedoes and to avoid detection, and he became the most decorated U-boat commander of the war. In March 1941, U-99 was sunk by the destroyer HMS Walker, and Kretschmer was captured, spending the rest of the war as a prisoner in Canada. His capture, and the capture of Prien’s and Schepke’s boats in the same month, marked the end of the first generation of U-boat aces, and the start of a new phase of the war in which the Allies had the advantage.

8. Fate

Losses in the Atlantic

Most Type VII boats were lost in action. Of the about 703 boats built, about 575 were sunk, and about 30,000 German submariners died, a casualty rate of about 75 per cent, the highest of any service in the war. The losses were heaviest in 1943 and 1944, when Allied aircraft, with radar and Leigh Lights, could find and sink U-boats on the surface at night, and escort carrier groups hunted them across the Atlantic. The Type VII, which had been designed for a war in which it could operate on the surface, was vulnerable to aircraft, and its slow submerged speed made it an easy victim for escorts. Some boats were lost to accidents, mines, and friendly fire, but most were sunk by aircraft, destroyers, and escort carriers. The last Type VII patrols, in 1945, were to the British coast and the Atlantic, and the boats that sailed often did not return. The war ended with the Type VII obsolete, overtaken by the Type XXI.

Survivors and Preservation

A handful of Type VII boats survived the war. U-995, a Type VIIC/41, is preserved at Laboe, Germany, as a museum ship, and U-505, a Type IXC, is preserved in Chicago. U-48, the most successful Type VIIB, was scuttled at the end of the war, and most of the surviving boats were divided among the Allies and scrapped or used for trials. The Type VII’s legacy is preserved in U-995, which is visited by hundreds of thousands of people each year, and in the records of the U-boat war, which show the Type VII as the boat that carried the war to its height and to its defeat. The boat’s design, which was a compromise between size, speed, and cost, set the pattern for post-war submarines, and its wolfpack tactics influenced submarine doctrine for decades.

9. Legacy

The Submarine That Defined the Battle

The Type VII defined the Battle of the Atlantic, and it remains the most famous submarine type of the Second World War. Its design, which balanced size, speed, and armament, set the standard for medium submarines, and its wolfpack tactics, which used radio direction to concentrate boats on a convoy, were a new way of waging war at sea. The Type VII also showed the limits of the submarine: it was a surface ship that could submerge, not a true submarine, and it depended on the surface for speed and for charging its batteries. The Allied countermeasures, radar, sonar, escort carriers, and long-range aircraft, exploited that dependence, and by 1943 the Type VII could not operate in the Atlantic without being found and sunk. The lesson was learned by the German navy, which replaced the Type VII with the Type XXI, a boat designed to stay submerged, and by the post-war navies, which built true submarines that could operate submerged for weeks.

Memory and the U-boat War

The Type VII is remembered in Germany as the boat that carried the U-boat war, and in Britain and America as the boat that threatened to starve Britain into surrender. The U-boat memorial at Laboe, where U-995 is preserved, commemorates the 30,000 German submariners who died, most of them in Type VII boats, and the memorials in Britain commemorate the merchant seamen who died in the ships the Type VII sank. The boat appears in films, novels, and histories of the war, most famously in the film Das Boot, which was based on a Type VIIC, U-96, and which showed the life of a U-boat crew in the Atlantic. For historians, the Type VII stands as an example of a weapon that was superbly suited to the war it was designed for, and that became obsolete when the enemy learned to counter it, a pattern that has repeated in naval warfare ever since.

10. Frequently Asked Questions

What was the Type VII U-boat?

The Type VII was a German medium submarine of the Second World War, and the most numerous submarine type ever built. About 703 Type VII boats were completed between 1936 and 1945, and they formed the backbone of the U-boat war in the Atlantic. It was a medium-sized, ocean-going boat, designed for operations in the North Sea and the western Atlantic, with a range of about 6,500 nautical miles on the surface. It carried a crew of about 44 to 52 men, five torpedo tubes and a deck gun, and it sank more Allied shipping than any other submarine type in history.

How many Type VII U-boats were built?

About 703 Type VII boats were built between 1936 and 1945, in the variants VIIA, VIIB, VIIC, VIIC/41, VIID and VIIF. The VIIC, with 568 boats, was the most numerous variant, and the Type VII as a whole was the most numerous submarine type ever built. The first boat, U-27, was launched in 1936, and production continued through the war, with boats ranging from the 64.5-metre VIIA to the 67.1-metre VIIC. The boats were medium-sized and ocean-going, with a surfaced speed of about 17.7 knots and a submerged speed of about 7.6 knots in the VIIC.

What was a wolfpack?

A wolfpack was a group of 10 to 20 U-boats that were directed by radio to a convoy and attacked together, at night, on the surface. The tactic was developed by Admiral Karl Donitz, and it was devastating in 1942, when U-boats sank large numbers of Allied ships. The Type VII was fast enough to keep up with a convoy on the surface, and quiet enough to evade escorts when submerged, which made the wolfpack tactic possible. Wolfpacks and the Battle of the Atlantic were the heart of the Type VII’s service, and the boat sank more Allied shipping than any other submarine type.

How many Type VII boats were lost?

About 575 of the about 703 Type VII boats were sunk, and about 30,000 German submariners died, a casualty rate of about 75 per cent. About 80 per cent of the boats were lost, the heaviest losses of any submarine type in the war. The Type VII sank more Allied shipping than any other submarine type in history, but that success came at a terrible cost in boats and men. About 703 boats were built between 1936 and 1945, and only a few survived, with a handful preserved as reminders of the U-boat war.

What was the Happy Time?

The Happy Time was the period from July 1940 to early 1941, when U-boats sank large numbers of Allied ships with few losses. The Allies had not yet introduced convoys and escort groups, so U-boats could attack merchant ships that sailed without protection. The Type VII was the standard boat of this period, fast enough on the surface to keep up with a convoy and armed with five torpedo tubes and a deck gun. The Happy Time ended as the Allies learned to protect their shipping, and the U-boat war became the long Battle of the Atlantic, in which about 575 Type VII boats were sunk.

How did the Type VII differ from the Type IX?

The Type VII was smaller, shorter-ranged and faster to dive than the Type IX, and it was the standard Atlantic boat. The Type IX was larger and longer-ranged, reserved for patrols off America and in the Indian Ocean, far from the Atlantic convoy routes. The Type VII, with a range of about 6,500 nautical miles on the surface, was designed for operations in the North Sea and the western Atlantic. The Type VII was built in far larger numbers than the Type IX, and it formed the backbone of the U-boat war in the Atlantic.

11. Sources

1. Wikipedia, “German Type VII submarine” — variants, production, specifications, and service.
2. Clay Blair, “Hitler’s U-Boat War: The Hunters, 1939-1942” and “The Hunted, 1942-1945” (Random House, 1996-1998) — the U-boat war and the wolfpacks.
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 VII” — boat lists, patrols, and losses.
5. Lothar-Gunther Buchheim, “Das Boot” (Piper, 1973) — life aboard a Type VIIC, U-96.
6. Jak P. Mallmann Showell, “U-boats in Camera” (Sutton, 1999) — photographs and service history.