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Keroman U-Boat Base
Keroman Submarine Base was a German U-boat base located in Lorient during World War II. Großadmiral Karl Dönitz decided to build the base on 28 June 1940. Between February 1941 and January 1942 three gigantic reinforced concrete structures were built on the Keroman peninsula. They are called K1, K2 and K3. In 1944 work began on a fourth structure. The base was capable of sheltering thirty submarines under cover. Although Lorient was heavily damaged by Allied bombing raids, this naval base survived through to the end of the war. Lorient was held until May 1945 by the Germans’ Wehrmacht Heer regular army forces, though surrounded by the American Army; the Germans refused to surrender.
Since they could not destroy the base and its submarine pens, the Allies had decided to flatten the city and port of Lorient to cut the supply lines to the U-boat bases. Without resupply of fuel, weapons (e.g. torpedoes), and provisions, it became impossible for those U-boats to return to war patrols in the Atlantic Ocean. Between 14 January 1943 and 17 February 1943, Allied aircraft dropped as many as 500 high-explosive bombs and more than 60,000 incendiary bombs on Lorient; nearly 90% of the city was flattened.
After the war, the base was used by the French Navy until 1997. Rechristened by the French as Base Ingénieur Général Stosskopf in July 1946, the new name commemorated Jacques Stosskopf, a German-speaking Alsatian Frenchman who had been the deputy director of naval construction for the Germans at the base while secretly in the French Resistance, and had given valuable information on submarine movements to the Allies during the war until his activities were discovered and he was killed.
At present, the Keroman U-boat base is open to the public. During tours, the submarine pens of block K3 can be seen. Its roof (3.40 to 7.0 metres (11.15 to 22.97 ft) of steel-reinforced concrete) can be visited, as well as a former anti-aircraft tower on top of the U-boat base. The tower affords an excellent view of the harbour and of the former headquarters of Großadmiral Karl Dönitz of the Kriegsmarine across the bay at Larmor-Plage. The FloreS645, a Daphné-class submarine, launched 1961, can also be visited. Another part of the base has been reconverted for industrial naval activities, with the preparation of racing multihulls.
The Type I U-boat was the first post–World War I attempt by Nazi Germany’s Kriegsmarine to produce an oceangoing submarine. Only two Type IAs were built, but the decision to halt production on further boats is believed to be because of political decisions and not because of major faults in the Type I design. Although the boats did not have any major design faults, they were known to be difficult to handle due to their poor stability and slow dive rate. The type was based on the design of the Finnish Vetehinen class and the Spanish Type E-1, designed by Ingenieurskantoor voor Scheepsbouw (the company also designed the Soviet S class submarine). The design later served as a basis for the development of other types of boats, primarily the VII and IX classes.
Constructed by Deschimag in Bremen, the first Type IA was launched on 14 February 1936. The two boats produced, U-25 and U-26, were primarily used as training vessels and for propaganda purposes to fly the Nazi flag. In 1940, the boats were called into combat duty due to the shortage of available submarines. Both boats experienced short, but successful combat careers. U-25 participated in five war cruises, sinking eight enemy ships. On 3 August 1940, while on a mine laying mission near Norway, U-25 struck a mine and sank with all hands on board.
U-26 carried out eight war cruises, sinking three merchant ships and damaging one British warship on its first mission laying mines. On its second war cruise, it became the first U-boat during World War II to enter the Mediterranean Sea. U-26 participated in three other successful war patrols, sinking four additional merchant ships. On its eighth war cruise the boat sunk three merchant ships and damaged another ship the next day. The attack on this ship led to severe depth-charging by two British warships, including HMS Gladiolus. Unable to dive, U-26 was forced to surface where she was bombed by a Sunderland flying boat. The crew scuttled the submarine and were rescued by Allied warships.
The Type II U-boat was designed by Nazi Germany as a coastal U-boat, modeled after the CV-707 submarine, which was designed by the Dutch dummy company NV Ingenieurskantoor voor Scheepsbouw den Haag (I.v.S) (set up by Germany after World War I in order to maintain and develop German submarine technology and to circumvent the limitations set by the Treaty of Versailles) and built in 1933 by the Finnish Crichton-Vulcan shipyard in Turku, Finland. It was too small to undertake sustained operations far away from the home support facilities. Its primary role was found to be in the training schools, preparing new German naval officers for command. It appeared in four sub-types.
Type VII U-boats were the most common type of German World War II U-boat. The Type VII was based on earlier German submarine designs going back to the World War I Type UB III and especially the cancelled Type UG, designed through the Dutch dummy company Ingenieurskantoor voor Scheepsbouw den Haag (I.v.S) which was set up by Germany after World War I in order to maintain and develop German submarine technology and to circumvent the limitations set by the Treaty of Versailles, and was built by shipyards around the world. The Finnish Vetehinen class and Spanish Type E-1 also provided some of the basis for the Type VII design. These designs led to the Type VII along with Type I, the latter being built in AG Weser shipyard in Bremen, Germany. The production of Type I was cut down only after two boats; the reasons for this are not certain and range from political decisions to faults of the type. The design of the Type I was further used in the development of the Type VII and Type IX. Type VII submarines were the most widely used U-boats of the war and were the most produced submarine class in history, with 703 built. The type had several modifications.
The Type VII was the most numerous U-boat type to be involved in the Battle of the Atlantic.
The Type IX U-boat was designed by Nazi Germany’s Kriegsmarine in 1935 and 1936 as a large ocean-going submarine for sustained operations far from the home support facilities. Type IX boats were briefly used for patrols off the eastern United States in an attempt to disrupt the stream of troops and supplies bound for Europe. The extended range came at the cost of longer dive times and decreased maneuverability. It was derived from the Type IA, and appeared in various sub-types.
Type IXs had six torpedo tubes; four at the bow and two at the stern. They carried six reloads internally and had five external torpedo containers (three at the stern and two at the bow) which stored ten additional torpedoes. The total of 22 torpedoes allowed U-boat commanders to follow a convoy and strike night after night. Some of the IXC boats were fitted for mine operations; as mine-layers they could carry 44 TMA or 66 TMB mines.
Secondary armament was provided by one 10.5 cm (4.1 in) deck gun with 180 rounds. Anti-aircraft armament differed throughout the war. They had two periscopes in the tower. Types IXA and IXB had an additional periscope in the control room, which was removed in Type IXC and afterward.
Type XXI U-boats, also known as “Elektroboote” (German: “electric boat”), were a class of German diesel-electric submarines designed during the Second World War. The submarines were rushed into production prematurely, and all of those built suffered from significant defects. As a result, only four of the submarines were completed during the war, and only two went on combat patrol with no action taken.
They were the first submarines designed to operate primarily submerged, rather than spending most of their time as surface ships that could submerge for brief periods as a means to escape detection or launch an attack. They incorporated a very large number of batteries to improve the time they could spend underwater, up to several days, and only surfaced to periscope depth for recharging via a Schnorchel. The design included a huge number of general improvements as well; much higher underwater speed through an improved hull design, greatly improved diving times, power assisted torpedo reloading, and greatly improved crew accommodations.
The design proved enormously influential in the post-war era. Several navies took XXIs on their lists and operated them for decades in various roles, and almost every navy introduced new submarine designs based on them. These include the Soviet Whisky , US Tang and the UK Porpoise, all of which were based on the XXI design to one degree or another. The basic design remains the basis for modern diesel-electric submarines to this day.