View source for Dora I

{{Short description|Former German submarine base and bunker in Norway}}
{{More citations needed|date=September 2011}}
{{Use dmy dates|date=June 2021}}
[[File:Dora 1 Trondheim.jpg|thumb|300px|Dora I, a former submarine bunker]]
'''Dora I''' (Dora 1) is a former [[Nazi Germany|German]] [[submarine base]] and [[submarine pen]] or [[bunker]] built in [[Trondheim]], [[Norway]]. Construction of the bunker (designated by the Germans as DORA I) was undertaken during the [[Second World War]]. Nearby is the uncompleted [[Dora II]] (Dora 2). Trondheim was traditionally referred to as ''Drontheim'' in German, and the name ''DORA'' is the letter "D" in the German [[Spelling alphabet|phonetic alphabet]].<ref>{{Cite web|url=http://www.battlefieldsww2.com/Dora_Trondheim.html|title=U-Boat base|publisher=Battlefieldsww2.com|access-date=13 March 2016|url-status=dead|archive-url=https://web.archive.org/web/20160303184248/http://www.battlefieldsww2.com/Dora_Trondheim.html|archive-date=3 March 2016}}</ref>

== History ==
{{Further|Nordstern (city)}}

===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 [[Second Armistice at Compiègne|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]] and [[Arctic Ocean]]s than Germany. Nevertheless, better protection for U-boats from aerial attack was required so a bunker-building programme was instigated.<ref>Jak P Mallmann Showell ''Hitler's U-boat Bases'' (2002) Sutton Publishing {{ISBN|0-7509-2606-6}} p. 55</ref>

[[German U-boat bases in occupied Norway]] operated between 1940 and 1945, when the [[Kriegsmarine]] (German navy), converted several naval bases in Norway into submarine bases. [[Trondheim]] 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]]s assigned to the flotilla during its service.<ref>{{Cite web|url=http://www.uboat.net/flotillas/13flo.htm|title=13th Flotilla|last=Helgason|first=Guðmundur|work=U-boat bases|publisher=Uboat.net|access-date=13 March 2016|archive-date=23 April 1999|archive-url=https://web.archive.org/web/19990423032525/http://www.uboat.net/flotillas/13flo.htm|url-status=live}}</ref>

===Construction===
[[Image:Baustelle Neuhafen - U-båtbunkeren Dora bygges (1942) (19199406238).jpg|thumb|left|Construction of the bunker]]
[[Image:The Campaign in North-west Europe 1944-45 BU6376.jpg|thumb|Three U-boats in a submarine pen at Trondheim, 19 May 1945]]
[[File:Captured German U-boats outside their pen at Trondheim in Norway, 19 May 1945. BU6382.jpg|thumb|German type VII and IX U-boats at Trondheim after the war on 19 May 1945]]
Construction of the bunker which would become part of the largest German naval base in [[Northern Europe]], started in the autumn of 1941, one year after the [[Operation Weserübung|invasion of Norway]]. The concrete roof was {{convert|3.5|m|ftin|abbr=on}} thick and reinforced with steel. The walls were also concrete but these were {{convert|3|m|ftin|abbr=on}} thick. The whole bunker was {{convert|153|x|105|m|yd|abbr=on}}. The work was undertaken by the [[Organisation Todt|Todt Organisation]]'s (OT) ''Einsatzgruppe'' 'Wiking' and the [[:de:Sager & Woerner|Sager & Wörner]] construction company from [[Munich]].

The OT used [[slave labour]] extensively; five [[Serbia]]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.<ref>[http://www.nrk.no/kultur/historien-om-dora-1.896221 NRK: Historien om Dora] {{Webarchive|url=https://web.archive.org/web/20190401093631/https://www.nrk.no/kultur/historien-om-dora-1.896221 |date=1 April 2019 }} {{in lang|no}}</ref>

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.<ref>Showell p.56</ref>

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.<ref name="Tåke">[https://www.nrk.no/trondelag/take-reddet-trondheim-fra-katastrofen-1.12699774 Tåke reddet Trondheim fra katastrofen] {{Webarchive|url=https://web.archive.org/web/20190402094129/https://www.nrk.no/trondelag/take-reddet-trondheim-fra-katastrofen-1.12699774 |date=2 April 2019 }} {{in lang|no}}</ref>

Construction of a smaller bunker just west of it, [[Dora II]] (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]]. Plans for a Dora III (Dora 3) in Leangen Bay (Leangenbukta) were postponed and construction never started.<ref name="Tåke"/>

===In service===
Dora I developed a noticeable sag of up to {{convert|15|cm|in|abbr=on}} which seemed to concern the builders more than the U-boat sailors. It was finally handed over to the ''[[Kriegsmarine]]'' on 20 June 1943 as the home base of the [[13th U-boat Flotilla]].<ref>Showell p.58</ref> The bunker, which could be [[hermetically sealed]] when attacked, had room for 16 [[U-boat]]s. A number of U-boats surrendered in Trondheim [[German U-boat bases in occupied Norway|at the end of the war]] on 9 May 1945.<ref>{{Cite web|url=http://uboat.net/fates/surrendered.htm|title=U-boat Fates|work=U-boat bases|publisher=Uboat.net|access-date=26 February 2017|archive-date=22 August 2019|archive-url=https://web.archive.org/web/20190822160104/https://www.uboat.net/fates/surrendered.htm|url-status=live}}</ref>

During the war [[Submarine pen#The Allied bombing offensive|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.<ref name="Tåke"/><ref>{{cite web|url=http://www.no-50-and-no-61-squadrons-association.co.uk/veterans-album-2/w-o-norman-goodfellow/|title=No.50 & No.61 Squadrons Association|access-date=26 February 2017|archive-date=27 February 2017|archive-url=https://web.archive.org/web/20170227062751/http://www.no-50-and-no-61-squadrons-association.co.uk/veterans-album-2/w-o-norman-goodfellow/|url-status=live}}</ref>

==After World War II==
[[Image:Dora 1 submarine piers.jpg|thumb|200px|Submarines could enter the base using these pens. For a closeup, click [[:Image:Dora 1 submarine pier closeup.jpg|here]]]]
After the war, Dora I was to be blown up using [[dynamite]], 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 [[Royal Norwegian Navy#History|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.{{citation needed|date=December 2019}} The base was used by the [[Norwegian Defence Force]]s; two extra stories, painted in blue, were added.

Dora I was converted into a warehouse and workshop building.{{citation needed|date=December 2019}} Today, the former naval base is the home of the city and [[State Archive in Trondheim|state]] 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 ==
<gallery perrow="5">
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.
</gallery>

==References==
;Notes
{{Reflist}}
;Bibliography
* [http://uboat.net/flotillas/bases/trondheim.html The Bases in Norway Trondheim] Uboat.net

== External links ==
{{Commons category|Dora, Trondheim}}
* [[Norsk Rikskringkasting|NRK]], [http://www.nrk.no/kultur/historien-om-dora-1.896221 Historien om Dora]{{in lang|no}}
* [https://web.archive.org/web/20160303184248/http://www.battlefieldsww2.com/Dora_Trondheim.html What remains of the Dora Bunker today]

{{Uboat}}

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[[Category:German Navy submarine bases]]
[[Category:Buildings and structures in Trondheim]]
[[Category:World War II sites of Nazi Germany]]
[[Category:1943 establishments in Norway]]
[[Category:Tourist attractions in Trondheim]]