Type VII submarine
The Type VII submarine is the most produced submarine class in history, with 709 boats commissioned between 1935 and 1945. At the start of the war on the 3rd of September 1939, only eighteen of them were in service. By the end, they had defined the Battle of the Atlantic and shaped the course of the war at sea. How did a medium-sized vessel, originally derived from World War I designs and built under cover of a Dutch dummy company, become the backbone of Nazi Germany's naval campaign? And how did a class that once terrorized Allied shipping end its days being sunk by its own crews in the waters of defeated Germany?
After Germany's defeat in World War I, the Treaty of Versailles banned the country from building submarines entirely. To get around this restriction, the Reichsmarine established a front company in the Netherlands called NV Ingenieurskantoor voor Scheepsbouw Den Haag, known as IvS. Working from the blueprints of the Type UB III and its never-built successors, IvS designed the Vetehinen class and in 1931 constructed three submarines in Finland.
By 1933, the Reichsmarine wanted a 500-tonne medium attack submarine capable of reaching the North Atlantic. Parts were manufactured in secret, but Hitler delayed assembly to avoid provoking Britain with an obvious breach of the Versailles treaty. The first formal orders for Type VII U-boats came in January 1935, months before Hitler publicly renounced the treaty in March 1935. The breach was eventually formalized through the Anglo-German Naval Agreement, under which Germany promised to keep its total U-boat tonnage at 45 percent of British submarine tonnage.
The design that emerged from this clandestine program was a single-hull vessel where the outer hull doubled as the pressure hull. Most of the fuel was stored inside the pressure hull rather than in the saddle tanks, which significantly reduced the risk of oil leaks if the outer skin was punctured by depth charges. The result was a vessel that could dive to a crush depth of 250 metres and reach a test depth of 150 metres, with a diving time from the surface of just 30 seconds.
Every Type VII carried four bow torpedo tubes and one stern tube, with up to eleven torpedoes aboard the earliest subtype. Two spare torpedoes rode externally in watertight containers, one forward of the conning tower and one behind it. Taking those external torpedoes inboard required opening a hatch, leaving the submarine unable to dive, so crews attempted it only in low-risk areas.
The Germans also developed sea mines that could pass through the standard torpedo tubes. A TMA moored mine measured 3.64 metres long and could be laid in waters up to 270 metres deep. Two TMA mines replaced each internal torpedo slot. The shorter TMB ground mine, at 2.31 metres, allowed three per torpedo slot. In November 1939 a heavier TMC ground mine, 3.39 metres long, entered service. A typical minelaying patrol in the early war years loaded eight TMA or twelve TMB mines and then continued with spare torpedoes for conventional attacks.
For surface engagements the Type VII carried an 8.8 cm quick-firing deck gun, primarily intended to finish off damaged ships and conserve torpedoes. The gun also served for stopping ships under prize law in the early months of the war. From the end of 1942 onward the deck gun was stripped to save weight for additional anti-aircraft weapons, reflecting how dramatically the tactical environment had changed. By mid-January 1943 single 2 cm C/38 guns were being installed, and the first quadruple C/38 mounting arrived in March. On the 30th of June 1943, U-boats were ordered to delay sailings until they had received the anti-aircraft upgrade. A naval version of the 3.7 cm Flak 43 eventually replaced the quadruple 2 cm mounting on the lower platform, and became standard by November 1943.
Ten Type VIIAs were built between 1935 and 1937, six at Deschimag AG Weser in Bremen and four at Friedrich Krupp Germaniawerft in Kiel. The first was laid down on the 11th of November 1935, launched on the 24th of June 1936, and commissioned on the 12th of August 1936. The VIIA had an externally mounted aft torpedo tube that could not be reloaded, a shortcoming addressed in later designs.
The Type VIIB that followed incorporated four specific improvements requested by the naval command: a smaller turning circle, better surface speed, greater range, and more torpedoes. Engineers moved the stern torpedo tube inside the pressure hull, between the two rudders, which allowed it to be reloaded and fired even on the surface. Fuel saddle tanks added 2500 nautical miles of range at 10 knots, pushing total surface range to 8700 nautical miles. Supercharged diesel engines pushed top speed to 17.9 knots in the Germaniawerft-powered version. Twenty-four VIIBs entered service between 1938 and 1941; twenty were lost at sea.
The Type VIIC grew out of a lesson from World War I, when many U-boats were lost in British minefields. The solution was to fit submarines with sonar, which required adding a 0.6 metre frame section in the control room. The irony is that after Germany captured French Atlantic bases in 1940, those waters were not threatened by minefields, so the sonar was never actually fitted to any Type VII. By the end of the war 577 Type VIICs had been built at fifteen shipyards, making it the dominant variant.
In 1941, engineers found a way to increase diving depth without redesigning the entire boat. By trimming 11.5 tonnes from the engine installation, they could add 10 tonnes of hull plating, thickening the steel from 18.5 mm to 21 mm and boosting diving depth by 20 percent. The bow was also extended by 13 centimetres to improve seaworthiness. This variant, the VIIC/41, had its first boat delivered on the 25th of August 1943. Production was cancelled on the 30th of September 1943 except at the small Flender Werke yard, which could not accommodate the newer submarine designs. There, the last VIIC/41 was laid down on the 28th of January 1944 and commissioned in January 1945.
Karl Donitz became supreme commander of the U-boat division in 1935 and from the beginning pushed for mass production of the Type VII, believing it was perfectly suited to his Wolfpack convoy tactics. The head of the German Navy, Erich Raeder, insisted on a more balanced fleet including minelayers, U-cruisers, and coastal submarines. The result was that at the outbreak of war, only 18 of the 56 commissioned U-boats were Type VIIs.
Those eighteen boats still managed two major early successes: one sank an aircraft carrier and another sank a battleship in the first two months of the war. In November 1939 an ambitious program called for 275 U-boats to be built annually, with 207 of them Type VIIs. By June 1940 shortages of skilled labor and raw materials forced a revision downward.
After the fall of France, U-boats operated from Atlantic bases far closer to the convoy lanes, and four Type VIIs distinguished themselves in what crews called the First Happy Time. One of those boats became the top-scoring U-boat of the entire war, with three successive commanders each earning the Knight's Cross of the Iron Cross for sinking more than a designated tonnage threshold. In 1941, Type VIIs sent to the Mediterranean sank an aircraft carrier and a battleship in quick succession, then in 1942 sank a third aircraft carrier during Operation Pedestal. Between September 1941 and April 1944, a total of 62 Type VIIs were transferred from the Atlantic force to the Mediterranean.
When the United States entered the war in December 1941, Type VIIs initially lacked the range to operate off the American East Coast. Commanders discovered that by running at very economical speeds and cramming every spare space with fuel and food, they could squeeze out one week of operations off Newfoundland and Labrador. With supply U-boat support, they reached as far as the Gulf of Mexico. Between December 1941 and August 1942, Type VIIs mounted 104 patrols to American waters and sank 225 ships. Type IXs, with longer range, ran 80 patrols and sank 384 ships in the same period.
On the 31st of December 1942, 199 attack U-boats were in service, with 148 of them Type VIIs. The convoy battles reached a peak in March 1943. On the 24th of May 1943, the U-boat command withdrew from the North Atlantic after suffering heavy losses and declining results. On the 1st of April 1944, all Type VIIs were ordered to stay in port in France and Norway in anticipation of the Allied landings, and they ultimately proved unable to affect Operation Overlord.
Up to mid-1941, German U-boats could receive spare torpedoes from surface supply ships at remote ocean locations. The sinking of the German battleship in May 1941 ended that arrangement, as the Royal Navy began hunting down every German surface supply vessel it could find. Towards the end of 1941, an attempt to resupply submarines from the auxiliary cruiser Atlantis ended in disaster when both Atlantis and her supply ship Python were sunk by a British cruiser.
Existing solutions were inadequate. The Type XIV supply boats carried only four spare torpedoes. The large Type XB minelayer could manage nine. Rather than design an entirely new vessel and drain the shipbuilding yards of engineering resources, the simplest answer was to add a 10.5-metre compartment to a standard Type VIIC, just as a similar section had been added for the VIID minelayer. The resulting Type VIIF could carry 20 spare torpedoes stored in four banks, and with saddle tanks extending along the extra compartment, its surface range reached 14700 nautical miles.
On the 22nd of August 1941, four VIIFs were ordered, with delivery expected at the start of 1943. When the four boats entered service, Allied air power had made torpedo resupply in battle zones too dangerous to attempt. Two were sent to resupply the Monsun Gruppe, a group of U-boats operating from Penang in Malaysia, while the others supplied remote bases in Norway.
On the 27th of August 1941, aircraft caught U-570 on the surface south of Iceland. Depth-charge damage left the crew unable to escape further attack and they surrendered. British ships towed the submarine to Iceland, where it was beached, repaired, and commissioned into the Royal Navy on the 31st of October 1941.
On the 1st of May 1942, another Type VII was badly damaged by aircraft east of Gibraltar and limped into the neutral Spanish port of Cartagena. Spanish authorities gave the crew three months for repairs, but the submarine could not be made seaworthy in time and was sold to Spain, entering Spanish service as S01. A Type VII destroyed at Toulon by air raids was repaired in 1945 and served in the French Navy as Millee until 1963. Three U-boats that surrendered in May 1945 entered service with the Royal Norwegian Navy as Kya, Kaura, and Kinn. Four others were allocated as war prizes to the Soviet Navy and renamed S-81, S-82, S-83, and S-48.
At the very end of the war, most of the surviving boats were sunk by their own crews in Operation Regenbogen. The British then disposed of the remainder in Operation Deadlight. The last surviving foreign operator decommissioned its Type VII in 1970. Today, the lone preserved example is a VIIC/41 on display at the Laboe Naval Memorial in Laboe, Schleswig-Holstein, Germany.
Common questions
How many Type VII submarines were built in total?
A total of 709 Type VII submarines were commissioned between 1935 and 1945, making them the most produced submarine class in history. The vast majority were Type VIICs, with 577 built at fifteen shipyards by the end of the war.
What was the Type VII submarine used for in World War II?
The Type VII was designed to attack Allied convoy lanes in the North Atlantic using Karl Donitz's Wolfpack tactics. It formed the backbone of Germany's effort in the Battle of the Atlantic and also served in the Mediterranean, Arctic, and American waters.
How did Germany build submarines after the Treaty of Versailles banned them?
Germany circumvented the ban by establishing a Dutch front company, NV Ingenieurskantoor voor Scheepsbouw Den Haag (IvS), which continued submarine design work in secret. IvS built three submarines in Finland in 1931 before Germany began openly ordering Type VIIs in January 1935.
What happened to the Type VII submarines at the end of World War II?
Most surviving Type VII U-boats were scuttled by their own crews in Operation Regenbogen. The British disposed of the remaining boats in Operation Deadlight. A small number entered foreign navies, with the last one decommissioned in 1970.
Where can you see a surviving Type VII submarine today?
The only preserved Type VII submarine is a VIIC/41 on display at the Laboe Naval Memorial in Laboe, Schleswig-Holstein, Germany.
What were the main subtypes of the Type VII U-boat?
The main subtypes were the VIIA (ten built, 1935-1937), VIIB (twenty-four built, improved range and armament), VIIC (577 built, the dominant variant), VIIC/41 (88 built, stronger pressure hull), VIID (six built, SMA minelayer), and VIIF (four built, torpedo supply submarine). The VIIC/42 and VIIC/43 were cancelled before any were commissioned.
All sources
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