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Dora I (Dora 1) is a former German
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 Bay, N ...
and submarine pen or
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 ...
built in
Trondheim Trondheim ( , , ; ), historically Kaupangen, Nidaros, and Trondhjem (), is a city and municipality in Trøndelag county, Norway. As of 2022, it had a population of 212,660. Trondheim is the third most populous municipality in Norway, and is ...
,
Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...
. Construction of the bunker (designated by the Germans as DORA I) was undertaken during the
Second World War World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
. Nearby is the uncompleted
Dora II Dora II (Dora 2) is an unfinished Nazi Germany, German submarine base and submarine pen or bunker in Trondheim, Norway, which is next to Dora I (Dora 1). Construction of the bunker (designated by the Germans as DORA II) was undertaken during the Se ...
(Dora 2). Trondheim was traditionally referred to as ''Drontheim'' in German, and the name ''DORA'' is the letter "D" in the German phonetic alphabet.


History


Background

Following the occupation of Norway in 1940, it was soon realised that the country only had limited facilities for minor naval repairs. More extensive work usually meant a return to Germany. The capitulation of France two months later overshadowed the strategic importance of Norway to some extent, but it was still regarded as a better location for access to the
Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...
and
Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions. It spans an area of approximately and is the coldest of the world's oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, ...
s than Germany. Nevertheless, better protection for U-boats from aerial attack was required so a bunker-building programme was instigated. German U-boat bases in occupied Norway operated between 1940 and 1945, when the
Kriegsmarine The (, ) was the navy of Nazi 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 military branch, branche ...
(German navy), converted several naval bases in Norway into submarine bases.
Trondheim Trondheim ( , , ; ), historically Kaupangen, Nidaros, and Trondhjem (), is a city and municipality in Trøndelag county, Norway. As of 2022, it had a population of 212,660. Trondheim is the third most populous municipality in Norway, and is ...
was an important U-boat base in Norway during the war. It was the home of the 13th U-boat Flotilla and it had 55
U-boat U-boats are Submarine#Military, naval submarines operated by Germany, including during the World War I, First and Second World Wars. The term is an Anglicization#Loanwords, anglicized form of the German word , a shortening of (), though the G ...
s assigned to the flotilla during its service.


Construction

Construction of the bunker which would become part of the largest German naval base in
Northern Europe The northern region of Europe has several definitions. A restrictive definition may describe northern Europe as being roughly north of the southern coast of the Baltic Sea, which is about 54th parallel north, 54°N, or may be based on other ge ...
, started in the autumn of 1941, one year after the invasion of Norway. The concrete roof was thick and reinforced with steel. The walls were also concrete but these were thick. The whole bunker was . The work was undertaken by the Todt Organisation's (OT) ''Einsatzgruppe'' 'Wiking' and the Sager & Wörner construction company from
Munich Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...
. The OT used slave labour extensively; five
Serbia , image_flag = Flag of Serbia.svg , national_motto = , image_coat = Coat of arms of Serbia.svg , national_anthem = () , image_map = , map_caption = Location of Serbia (gree ...
n workers died when a wall fell on them. This incident fuelled a widespread rumor that the Germans simply left the bodies inside the wall. While German engineers did calculate that the five bodies would not weaken the fortification considerably, the bodies were removed before construction continued. Difficulties with the labour force was not the only problem. The acquisition of raw materials was also a problem. Many Norwegian buildings were erected from timber so cement, sand and aggregate - components essential for the production of concrete - were often hard to extract in sufficient quantities. The steel required for reinforcing was mostly imported from Germany. The weather also played its part; roads and railways were often affected by snow and ice. Pre-fabricated accommodation units from Germany proved to be inadequate. More ships were delayed by the weather than enemy interference. Most construction machinery also had to be imported. The bunkers in Norway were originally slated for a second floor to be built over the submarine pens. This was to house accommodation, workshops and offices. The idea was abandoned at the end of 1941 due to the problems already mentioned. The choice of site did not help either. Accumulated mud, on top of clay and sand layers proved to be incompatible with existing designs and was unstable ground so that the bunker had to be built in parts and stabilized before continuing construction.Tåke reddet Trondheim fra katastrofen
Construction of a smaller bunker just west of it,
Dora II Dora II (Dora 2) is an unfinished Nazi Germany, German submarine base and submarine pen or bunker in Trondheim, Norway, which is next to Dora I (Dora 1). Construction of the bunker (designated by the Germans as DORA II) was undertaken during the Se ...
(Dora 2), was started in 1942, but it was only half-completed by the end of the war. This building is presently used by a
shipyard A shipyard, also called a dockyard or boatyard, is a place where ships are shipbuilding, built and repaired. These can be yachts, military vessels, cruise liners or other cargo or passenger ships. Compared to shipyards, which are sometimes m ...
. Plans for a Dora III (Dora 3) in Leangen Bay (Leangenbukta) were postponed and construction never started.


In service

Dora I developed a noticeable sag of up to which seemed to concern the builders more than the U-boat sailors. It was finally handed over to the ''
Kriegsmarine The (, ) was the navy of Nazi 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 military branch, branche ...
'' on 20 June 1943 as the home base of the 13th U-boat Flotilla. The bunker, which could be
hermetically sealed A hermetic seal is any type of sealing that makes a given object airtight (preventing the passage of air, oxygen, or other gases). The term originally applied to airtight glass containers but, as technology advanced, it applied to a larger ca ...
when attacked, had room for 16
U-boat U-boats are Submarine#Military, naval submarines operated by Germany, including during the World War I, First and Second World Wars. The term is an Anglicization#Loanwords, anglicized form of the German word , a shortening of (), though the G ...
s. A number of U-boats surrendered in Trondheim at the end of the war on 9 May 1945. During the war Allied bombing raids targeted German submarine pens (bunkers). In July 1943 an American bombing raid was conducted against the German base at Trondheim. Workshops in the area were destroyed, there was large material damage including on civilian targets, and the German reports were that they were set back three months in their construction plans (loss of materials and other damage would have contributed to delays on building Dora II). Only light damage was ever reported on Dora I. A British bombing raid was attempted in November 1944, but because of low cloud cover/fog and smoke laying by the Germans the bombers turned back and did not bomb Trondheim.


After World War II

After the war, Dora I was to be blown up using
dynamite Dynamite is an explosive made of nitroglycerin, sorbents (such as powdered shells or clay), and Stabilizer (chemistry), stabilizers. It was invented by the Swedish people, Swedish chemist and engineer Alfred Nobel in Geesthacht, Northern German ...
, but this project was eventually cancelled due to the massive construction and the sheer size of the bunker. Blowing it up would have caused serious damage to the surrounding buildings as well. In the summer of 1945 the Norwegian submarine force were transferred from Britain and Dora I was used by them until 1954, when they were moved to the submarine pens in Bergen. The base was used by the Norwegian Defence Forces; two extra stories, painted in blue, were added. Dora I was converted into a warehouse and workshop building. Today, the former naval base is the home of the city and
state State most commonly refers to: * State (polity), a centralized political organization that regulates law and society within a territory **Sovereign state, a sovereign polity in international law, commonly referred to as a country **Nation state, a ...
archives, a bowling alley and several other businesses. The submarine pens originally built for holding German U-boats are now being used as a harbour for civilian boats.


Gallery

Image:Dora1-FullFrontView.jpg, Full front view of complex. Image:Dora1-Corner.JPG, Corner view, shows thickness of concrete. Image:Dora1-FjordGates.JPG, Recently, the fjord side has been under renovation. Image:Dora1-FrontRamps.JPG, Close up of drive-up ramps on front side. Image:Dora1-Map(WithDora2).jpg, Sign showing buildings in the fjord harbour area with arrows added to point to the Dora complexes.


References

;Notes ;Bibliography
The Bases in Norway Trondheim
Uboat.net


External links

*
NRK The Norwegian Broadcasting Corporation (), commonly known by its initialism NRK, is a Norwegian state-run, government-influenced radio and television public broadcasting company. The NRK broadcasts three national TV channels and thirteen nat ...

Historien om Dora


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