A submarine pen (''U-Boot-Bunker'' in German) is a type of
submarine base
A submarine base is a military base that shelters submarines and their personnel.
Examples of present-day submarine bases include HMNB Clyde, Île Longue (the base for France's Force océanique stratégique), Naval Submarine Base Kings Ba ...
that acts as a
bunker
A bunker is a defensive military fortification designed to protect people and valued materials from falling bombs, artillery, or other attacks. Bunkers are almost always underground, in contrast to blockhouses which are mostly above ground. T ...
to protect
submarines
A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely ...
from air attack.
The term is generally applied to submarine bases constructed during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, particularly in Germany and its occupied countries, which were also known as U-boat pens (after the phrase "
U-boat
U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare ro ...
" to refer to German submarines).
Background
Among the first forms of protection for submarines were some open-sided shelters with partial wooden foundations that were constructed during
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
. These structures were built at the time when bombs were light enough to be dropped by hand from the cockpit. By the 1940s, the quality of aerial weapons and the means to deliver them had improved markedly.
The mid-1930s saw the Naval Construction Office in
Berlin
Berlin is Capital of Germany, the capital and largest city of Germany, both by area and List of cities in Germany by population, by population. Its more than 3.85 million inhabitants make it the European Union's List of cities in the European U ...
give the problem serious thought. Various factions in the navy were convinced protection for the expanding
U-boat arm
The (, ) was the navy of Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war (1919–1935) of the Weimar Republic. The was one of three official branches, along with the ...
was required. A
Royal Air Force
The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...
(RAF) raid on the capital in 1940, the occupation of France and Britain's refusal to surrender triggered a massive building programme of submarine pens and air raid shelters.
By the autumn of 1940, construction of the "Elbe II" bunker in
Hamburg
Hamburg (, ; nds, label=Hamburg German, Low Saxon, Hamborg ), officially the Free and Hanseatic City of Hamburg (german: Freie und Hansestadt Hamburg; nds, label=Low Saxon, Friee un Hansestadt Hamborg),. is the List of cities in Germany by popul ...
and "Nordsee III" on the island of
Heligoland
Heligoland (; german: Helgoland, ; Heligolandic Frisian: , , Mooring Frisian: , da, Helgoland) is a small archipelago in the North Sea. A part of the German state of Schleswig-Holstein since 1890, the islands were historically possessions ...
was under way. Others swiftly followed.
General
It was soon realised that such a massive project was beyond the ''
Kriegsmarine
The (, ) was the navy of Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war (1919–1935) of the Weimar Republic. The was one of three official branches, along with th ...
'', and the
Todt Organisation (OT) was brought in to oversee the administration of labour. The local supply of such items as sand, aggregate, cement, and timber was often a cause for concern. The steel required was mostly imported from Germany. The attitudes of the people in France and Norway were significantly different. In France there was generally no problem with the recruitment of men and the procurement of machinery and raw materials. It was a different story in Norway. There, the local population were far more reluctant to help the Germans. Indeed, most labour had to be brought in. The ground selected for bunker construction was no help either: usually being at the head of a
fjord
In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Germany, Greenland, the Faroe Islands, Icela ...
, the foundations and footings had to be hewn out of granite. Several metres of silt also had to be overcome. Many of the workers needed were
forced labour, most especially the
concentration camp
Internment is the imprisonment of people, commonly in large groups, without charges or intent to file charges. The term is especially used for the confinement "of enemy citizens in wartime or of terrorism suspects". Thus, while it can simp ...
inmates supplied by the ''
Schutzstaffel
The ''Schutzstaffel'' (SS; also stylized as ''ᛋᛋ'' with Armanen runes; ; "Protection Squadron") was a major paramilitary organization under Adolf Hitler and the Nazi Party in Nazi Germany, and later throughout German-occupied Europe d ...
'' from camps near the pens.
The incessant air raids caused serious disruption to the project, hampering the supply of material, destroying machinery, and harassing the workers. Machinery such as excavators,
pile drivers, cranes, floodlighting, and
concrete pumps (which were still a relatively new technology in the 1940s) was temperamental, and in the case of steam-driven equipment, very noisy.
Bunkers had to be able to accommodate more than just U-boats; space had to be found for offices, medical facilities, communications, lavatories, generators, ventilators,
anti-aircraft guns, accommodation for key personnel such as crewmen, workshops,
water purification
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for hu ...
plants, electrical equipment, and radio testing facilities. Storage space for spares, explosives, ammunition, and oil was also required.
Types of bunker
Four types of bunker were constructed:
* Covered lock
: These were bunkers built over an existing
lock to give a U-boat some protection while it was at its most vulnerable – i.e. when the lock was emptying or filling. They were usually constructed with new locks alongside an existing structure.
* Construction bunker
: Used for building new boats
* Fitting-out bunkers
: After launch, many U-boats were fitted-out under their protection
* Shelter for operational boats and repair bunkers
: This was the most numerous type. There were two types that were built either on dry land or over the water. The former meant that U-boats had to be moved on ramps; the latter enabled the boats to come and go at will. Pumping the water out enabled dry dock repairs to be carried out. Some bunkers were large enough to allow the removal of periscopes and aerials.
There is no truth in the rumour of an underground bunker on
Fuerteventura
Fuerteventura () is one of the Canary Islands, in the Atlantic Ocean, part of the North Africa region, and politically part of Spain. It is located away from the northwestern coast of Africa. The island was declared a biosphere reserve by UNES ...
in the
Canary Islands
The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Mo ...
. This story was gleaned from a similar situation in
Le Havre
Le Havre (, ; nrf, Lé Hâvre ) is a port city in the Seine-Maritime department in the Normandy region of northern France. It is situated on the right bank of the estuary of the river Seine on the Channel southwest of the Pays de Caux, ver ...
in France when captured U-boat men were interrogated by the British.
Locations
Pens were constructed in the northern coastal ports of the ''Reich'' and in many occupied countries.
Germany
Pens protecting construction of the
Type XXI submarine were located in Hamburg (
Blohm & Voss
Blohm+Voss (B+V), also written historically as Blohm & Voss, Blohm und Voß etc., is a German shipbuilding and engineering company. Founded in Hamburg in 1877 to specialise in steel-hulled ships, its most famous product was the World War II battle ...
),
Bremen
Bremen (Low German also: ''Breem'' or ''Bräm''), officially the City Municipality of Bremen (german: Stadtgemeinde Bremen, ), is the capital of the Germany, German States of Germany, state Bremen (state), Free Hanseatic City of Bremen (''Freie H ...
(
AG Weser), and Danzig (
F. Schichau).
Bremen

The "Hornisse" bunker was not started until 1944 in
Bremen
Bremen (Low German also: ''Breem'' or ''Bräm''), officially the City Municipality of Bremen (german: Stadtgemeinde Bremen, ), is the capital of the Germany, German States of Germany, state Bremen (state), Free Hanseatic City of Bremen (''Freie H ...
; it was never completed.
"
Valentin
Valentin is a male given name meaning "strong, healthy, power, rule, terco". It comes from the Latin name ''Valentinus'', as in Saint Valentin. Commonly found in Spain, Romania, Bulgaria, France, Italy, Russia, Ukraine, Scandinavia, Latin America ...
" was the largest bunker in Germany. Begun in 1943, it was built to be a manufacturing facility, where Type XXI submarines were to be constructed. It too was never completed. Post-war, it was briefly used as a test site for British and American bombs (most of the damage done to the bunker was inflicted at this time) before becoming a storage facility for the German Navy. The labour to construct it was supplied by local concentration camps such as
Neuengamme in Hamburg.
:Valentin:
:Hornisse:
Hamburg
The city was the site of two structures, "Elbe II" and "Fink II". The
Finkenwerder bunker was constructed by 1,700
slave labour
Slavery and enslavement are both the state and the condition of being a slave—someone forbidden to quit one's service for an enslaver, and who is treated by the enslaver as property. Slavery typically involves slaves being made to perf ...
ers over four years. After capture, it was demolished with 32 tonnes of bombs.
:Elbe II:
:Fink II:
Helgoland
The "Nordsee III" bunker in
Helgoland was one of the oldest submarine pens, being started in 1940. It was left alone until near the end of the war when it was attacked by the RAF and like most of the facilities on the island, completely destroyed. It was also used after the end of the war for testing new weapons. No trace of the pen has survived.
:
Kiel
This town was constantly bombed in World War II, the targets often being the "Kilian" and "Konrad" bunkers. They were started in 1941 and 1942 respectively. The latter was used for the construction of ''
Seehund''
midget submarine
A midget submarine (also called a mini submarine) is any submarine under 150 tons, typically operated by a crew of one or two but sometimes up to six or nine, with little or no on-board living accommodation. They normally work with mother ships, ...
s.
It was in "Kilian" that was probably the only submarine to be lost in a bunker. Misguided bombs from an air raid on the town caused what might today be called a ''tsunami'' to cross the ''Förde'' and enter the bunker. ''Oberleutenant zur See'' Hans-Gerold Hauber, the captain of , had courted ridicule by ordering all hatches on his boat to be closed, despite being in the bunker. "This simple precaution saved ''U-170'' from sinking while lying next to ''U-4708''".
Wilhelmshaven
A U-boat bunker in
Wilhelmshaven
Wilhelmshaven (, ''Wilhelm's Harbour''; Northern Low Saxon: ''Willemshaven'') is a coastal town in Lower Saxony, Germany. It is situated on the western side of the Jade Bight, a bay of the North Sea, and has a population of 76,089. Wilhelms ...
was planned, but it never got beyond the preliminary stage.
France
The German occupying forces built many U-boat pens in the Atlantic ports of France in
Bordeaux
Bordeaux ( , ; Gascon oc, Bordèu ; eu, Bordele; it, Bordò; es, Burdeos) is a port city on the river Garonne in the Gironde department, Southwestern France. It is the capital of the Nouvelle-Aquitaine region, as well as the prefecture ...
,
Brest,
La Rochelle
La Rochelle (, , ; Poitevin-Saintongeais: ''La Rochéle''; oc, La Rochèla ) is a city on the west coast of France and a seaport on the Bay of Biscay, a part of the Atlantic Ocean. It is the capital of the Charente-Maritime department. Wit ...
/
La Pallice
La Pallice (also known as ''grand port maritime de La Rochelle'') is the commercial deep-water port of La Rochelle, France.
During the Fall of France, on 19 June 1940, approximately 6,000 Polish soldiers in exile under the command of Stanisł ...
,
Lorient
Lorient (; ) is a town ('' commune'') and seaport in the Morbihan department of Brittany in western France.
History
Prehistory and classical antiquity
Beginning around 3000 BC, settlements in the area of Lorient are attested by the presen ...
, and
St. Nazaire
Saint-Nazaire (; ; Gallo: ''Saint-Nazère/Saint-Nazaer'') is a commune in the Loire-Atlantique department in western France, in traditional Brittany.
The town has a major harbour on the right bank of the Loire estuary, near the Atlantic Ocean. T ...
. Almost 4.4 million cubic metres of concrete were used.
Bordeaux

An unnamed bunker and bunkered lock were constructed in Bordeaux, the fourth largest French city at the start of the war. Both structures were started in 1941; the bunkered lock was not finished by war's end. The main building was larger than those in other locations; this was to allow supply boats and
minelayer
A minelayer is any warship, submarine or military aircraft deploying explosive mines. Since World War I the term "minelayer" refers specifically to a naval ship used for deploying naval mines. "Mine planting" was the term for installing contro ...
s to use it. The
Royal Italian Navy
The ''Regia Marina'' (; ) was the navy of the Kingdom of Italy (''Regno d'Italia'') from 1861 to 1946. In 1946, with the Italian constitutional referendum, 1946, birth of the Italian Republic (''Repubblica Italiana''), the ''Regia Marina'' ch ...
established the
Betasom base at Bordeaux. The port was also the target of a British
commando
40_Commando.html" ;"title="Royal Marines from 40 Commando">Royal Marines from 40 Commando on patrol in the Sangin area of Afghanistan are pictured
A commando is a combatant, or operative of an elite light infantry or special operations forc ...
raid – the so-called
Cockleshell Heroes.
:
Brest

The
Brittany
Brittany (; french: link=no, Bretagne ; br, Breizh, or ; Gallo: ''Bertaèyn'' ) is a peninsula, historical country and cultural area in the west of modern France, covering the western part of what was known as Armorica during the period o ...
port only had one bunker, but it was the largest; it was also unnamed. Started in 1941, the plans were modified many times before completion a year later.
By February 1942 the RAF had lost interest in the area; most of the town had already been destroyed and they did not possess large enough bombs to seriously threaten the bunker. Between February 1942 and early 1943, apart from a few American aircraft, the place was left alone. The German garrison surrendered to US forces in September 1944. They had had sufficient explosives to cripple the bunker but did not use them due to the proximity of a hospital.
:
La Rochelle/La Pallice

Only separate La Rochelle and La Pallice so they are usually considered as one port. An unnamed bunker was built at La Pallice (); it was started in April 1941.
[ Similar building techniques to those used in St. Nazaire were employed. Due to the relative ease of construction, the main structure was ready for its first U-boats six months later. A bunkered lock was begun in June 1942. It was completed in March 1944. Scenes for the 1981 films '']Das Boot
''Das Boot'' (, English: "The Boat") is a 1981 West German war film written and directed by Wolfgang Petersen, produced by Günter Rohrbach, and starring Jürgen Prochnow, Herbert Grönemeyer, and Klaus Wennemann. It has been exhibited both ...
'' and ''Raiders of the Lost Ark
''Raiders of the Lost Ark'' is a 1981 American action-adventure film directed by Steven Spielberg and written by Lawrence Kasdan, based on a story by George Lucas and Philip Kaufman. It stars Harrison Ford, Karen Allen, Paul Freeman, R ...
'' were shot in La Pallice.
:
Lorient
The largest U-boat base was the Lorient Submarine Base in Brittany. Three bunkers, "Keroman I", "II" and "III", the "Scorff" bunker and two "Dom" bunkers, east and west, were all begun in 1941. Two more were in the planning stage.
"Keroman I" was unique in that it required its U-boats to be "hauled out of the water, placed on a many-wheeled buggy and then transported into the bunker on a sliding bridge system." This arrangement might have been more vulnerable to air raids, but damage was minimal and it had the advantage of the U-boat not needing a dry dock. "Keroman II", being landlocked, was served by the same system.
:Keroman I:
:Keroman II:
"Keroman III" was more conventional, as was the "Scorff" bunker. The two "Dom" bunkers (so-called because of their resemblance to the religious building, ''Dom'' means 'cathedral' in German) were located around a massive turntable which fed U-boats into the covered repair bays.
: Keroman III:
: Scorff:
:Dom (East):
: Dom (West):
Karl Dönitz
Karl Dönitz (sometimes spelled Doenitz; ; 16 September 1891 24 December 1980) was a Nazi Germany, German admiral who briefly succeeded Adolf Hitler as head of state in May 1945, holding the position until the dissolution of the Flensburg Gov ...
, head of the U-boat arm and later the chief of the ''Kriegsmarine'', had his headquarters at nearby Kernevel.
St-Nazaire
The construction of the Saint-Nazaire submarine base was commenced in 1941, including a bunkered lock. (Elsewhere in the reference, it states that "the excavations" for the bunkered lock were begun in October 1942).
:
The pens were not affected by the British commando raid in March 1942, whose main objective were the ''Normandie'' dock gates.
Norway
Norway is to some extent ruled by its weather. Building submarine pens was often hampered by snow and ice; the ground might have been chosen, but the occupation of France only a few months after Norway's surrender rather overshadowed the Scandinavian country as far as bunkers for U-boats was concerned. Nonetheless, a requirement for protection was identified. With the liberation of France
The liberation of France in the Second World War was accomplished through diplomacy, politics and the combined military efforts of the Allied Powers, Free French forces in London and Africa, as well as the French Resistance.
Nazi Germany inv ...
in 1944, Norway regained its importance, but for barely a year.
The Norwegian bunkers in Bergen
Bergen (), historically Bjørgvin, is a city and municipality in Vestland county on the west coast of Norway. , its population is roughly 285,900. Bergen is the second-largest city in Norway. The municipality covers and is on the peninsula o ...
and Trondheim
Trondheim ( , , ; sma, Tråante), historically Kaupangen, Nidaros and Trondhjem (), is a city and municipality in Trøndelag county, Norway. As of 2020, it had a population of 205,332, was the third most populous municipality in Norway, an ...
were originally designed to have two floors, the lower one for U-boats, the upper one for accommodation, workshops and offices. However, with the project running six months late, plans for the second storey were abandoned.
Bergen
Control of the Bergen project came under the German Naval Dockyard. Construction of "Bruno" commenced in 1941, with a Munich-based firm taking the lead. A shortage of labour, along with the acquisition of raw materials in sufficient quantities and poor weather, was always going to cause problems. Specialised machinery had to be imported, as did accommodation that could stand up to the harsh Norwegian winter.
In a bid to increase its protection, the bunker had granite
Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies und ...
blocks, each about a cubic metre in size, positioned on its roof. The shortage of cement ensured that the blocks could not be properly stuck down.
Trondheim
" Dora I" was started in 1941, shortly after Operation Barbarossa
Operation Barbarossa (german: link=no, Unternehmen Barbarossa; ) was the invasion of the Soviet Union by Nazi Germany and many of its Axis allies, starting on Sunday, 22 June 1941, during the Second World War. The operation, code-named afte ...
, the invasion of the Soviet Union. It was constructed by Soviet prisoners of war. Despite any number of precautions being taken when putting in the foundations, "Dora I" developed a noticeable sag of . It did not seem to bother the submariners as much as the builders. Work on " Dora II" started in 1942, but it was not completed by the end of the war.
The Allied bombing offensive
U-boat facilities first became a bombing priority in March 1941 and again during the Combined Bomber Offensive
The Combined Bomber Offensive (CBO) was an Allied offensive of strategic bombing during World War II in Europe. The primary portion of the CBO was directed against Luftwaffe targets which was the highest priority from June 1943 to 1 April 1944. T ...
. The bunkers did not suffer as much as their surroundings until August 1944 when a new type of bomb was used against them, the " Tallboy" bomb.
U-boat yards and pens were the primary objectives for the US Eighth Air Force
The Eighth Air Force (Air Forces Strategic) is a numbered air force (NAF) of the United States Air Force's Air Force Global Strike Command (AFGSC). It is headquartered at Barksdale Air Force Base, Louisiana. The command serves as Air Forces ...
from late 1942 to early 1943.[Gurney] In the course of the war, the Allies used various tactics and weaponry against German U-boat pens. For example, The United States Army Air Forces
The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...
, as part of Operation Aphrodite
Aphrodite and Anvil were the World War II code names of United States Army Air Forces and United States Navy operations to use Boeing B-17 Flying Fortress and Consolidated PB4Y bombers as precision-guided munitions against bunkers and other har ...
, used US designed and operated radio-controlled aircraft, "Bat" guided bombs. Whereas the RAF Bomber Command
RAF Bomber Command controlled the Royal Air Force's bomber forces from 1936 to 1968. Along with the United States Army Air Forces, it played the central role in the Strategic bombing during World War II#Europe, strategic bombing of Germany in W ...
, used the Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by Kingdom of England, English and Kingdom of Scotland, Scottish kings from the early medieval period, the first major maritime engagements were foug ...
designed "Disney" rocket-assisted bombs, and the Barnes Wallis
Sir Barnes Neville Wallis (26 September 1887 – 30 October 1979) was an English engineer and inventor. He is best known for inventing the bouncing bomb used by the Royal Air Force in Operation Chastise (the "Dambusters" raid) to attac ...
devised Tallboy and Grand Slam deep penetration bombs.
A U-boat pen concrete target had been built at Ashley Walk bombing range in the New Forest
The New Forest is one of the largest remaining tracts of unenclosed pasture land, heathland and forest in Southern England, covering southwest Hampshire and southeast Wiltshire. It was proclaimed a royal forest by William the Conquero ...
, Hampshire, to assist in preparation for these raids. It consisted of a concrete roof covering three shallow "pens". After the war it was buried in an earth mound, although its edges are once again visible in places due to weathering.
Post war
Yugoslavia
The Yugoslav People's Army
The Yugoslav People's Army (abbreviated as JNA/; Macedonian and sr-Cyrl-Latn, Југословенска народна армија, Jugoslovenska narodna armija; Croatian and bs, Jugoslavenska narodna armija; sl, Jugoslovanska ljudska arm ...
used submarine pens as well, including ones on the islands of Vis and Brač or in Kotor Bay, carved inside natural hills. The ones in Montenegro
)
, image_map = Europe-Montenegro.svg
, map_caption =
, image_map2 =
, capital = Podgorica
, coordinates =
, largest_city = capital
, official_languages = ...
fulfilled their purpose, housing and protecting the submarines and missile boat
A missile boat or missile cutter is a small, fast warship armed with anti-ship missiles. Being smaller than other warships such as destroyers and frigates, missile boats are popular with nations interested in forming a navy at lower cost. They ...
s from NATO
The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two No ...
aerial attacks during Operation Allied Force
The North Atlantic Treaty Organization (NATO) carried out an aerial bombing campaign against the Federal Republic of Yugoslavia during the Kosovo War. The air strikes lasted from 24 March 1999 to 10 June 1999. The bombings continued until an a ...
in 1999. They are now abandoned and freely accessible from sea or by foot.
file:Vojni potkop Parja Vis 01.JPG, Vis - Location:
file:Brač submarine bunker.jpg, Brač
See also
* Muskö naval base
Muskö Naval Base is a Swedish underground naval facility on the island of Muskö just south of Stockholm in Haninge Municipality (Haninge Kommun).
The construction of the base started in 1950 and was completed 19 years later in 1969. Durin ...
(Sweden)
* Naval museum complex Balaklava
Naval museum complex Balaklava ( uk, Морський музейний комплекс "Балаклава", Russian: Музей холодной войны, "The Cold War Museum", designation K-825) is an underground submarine base in Balak ...
(includes several cold war era submarine pens)
* Yulin Naval Base (China)
Notes
Bibliography
*
External links
German World War II U-boat pens in France
{{DEFAULTSORT:Submarine Pen
Bunkers
*
World War II strategic bombing