| Valentin Submarine Pens | |
|---|---|
| Part of Third Reich | |
| Farge port (Weser River, Bremen) | |
2006 remains of Valentin submarine pen |
|
| Type | blockhouse |
| Built | February 1943 to March 1945 (unfinished) |
| Construction materials |
Ferrous concrete |
The Valentin submarine pens are a protective shelter built to construct German U-boats during World War II at Farge, a small port on the Weser River in Bremen. The pens were under construction from 1943 to March 1945 using forced labour, but were damaged by air-raids and unfinished by the end of the war. The Valentin U-boat pens were the largest fortified pens in Germany, and were second only to those built at Brest in France.
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Production of U-boats by German shipyards had been dramatically reduced by bombing by the Royal Air Force and the United States Army Air Forces. So a bomb-proof production site was planned, under the codename Valentin, to be built at the port of Farge. It was intended the facility would be used for the final assembly of Type XXI submarines.
The bunker is around 426 metres (1,398 ft) long and 97 metres (318 ft) wide at the widest point; the walls are 4.5 metres (15 ft) thick. The height of the structure is between 22.5 and 27 metres (74 and 89 ft). The roof was constructed using dozens of large, reinforced concrete arches, manufactured on-site and individually lifted into place. Most of the roof is around 4.5 metres (15 ft) thick but part of it is 7 metres (23 ft) thick as the Germans began adding to its thickness before the bunker was even completed. Construction required 650,000 cubic yards (500,000 m3) of concrete.[1]
After completion, the bunker would have a work–force of around 4,500 slave workers.[2] Each U-boat would be assembled from eight, large, pre-fabricated sections that were manufactured elsewhere. The bunker was to house 13 assembly bays, each carrying out one part of the assembly process, two bays were underneath box-like structures on the roof that allowed the extra height needed for the installation of periscopes and Submarine snorkels. The final bay housed an 8 metres (26 ft) deep pool of water. It was fitted with large, water-tight doors like a water lock; with the doors closed, the entire bay could be flooded to leak–test completed U-boats. A large door in the west wall opened onto the Weser river; through this, sections of submarine would be delivered by barge, and completed submarines would leave.[1]
It was intended that Valentin would commence production in late 1944, but this was postponed to mid-1945. However, if Valentin had been commissioned it is likely production would have been limited unless severe quality control problems with the prefabricated sections could have been solved (Albert Speer had directed the sections should be made by inland companies with little experience in shipbuilding). The Type XXI submarines assembled in other shipyards required lengthy re-working to fix flaws in the sections; out of the 118 boats completed, only four were rated fit for combat before the war ended in Europe.[3]
The design, and oversight of the Valentin's construction, was carried out by Organisation Todt. Marineoberbaurat Edo Meiners was in charge overall; the on-site supervising engineer was Erich Lackner.[4] He had a lengthy post-war career, becoming one of Germany's most important civil engineers.
Most of the 10,000-12,000 who built Valentin were slave workers,[5] some housed in the nearby Bremen-Farge concentration camp, a satellite camp of the Neuengamme concentration camp complex.[5] The camp was sited at a large naval fuel oil storage facility; some prisoners were accommodated in an empty underground fuel tank.
The camp was initially run by the SS, but the expansion of the camp network in the area led to a shortage of personnel. By the summer of 1944, the camp was commanded by an army captain, Ulrich Wahl, and the prisoners were guarded by a detachment of naval infantry.[5] Only a handful of SS men remained involved in the running of the camp.[5]
The prisoners included German criminals and political prisoners,[Note 1], non–German civilian workers (Fremdarbeiter) as well as Russian, Polish, French and Greek prisoners of war.[5]
Work on the bunker took place around the clock, with workers forced to work 12-hour shifts. This resulted in a high death rate amongst prisoners. However, only the deaths of 553 French prisoners have been confirmed.[5] The total number of deaths may be as high as 6000 as the names of the Polish and Russian dead were not recorded.
By March 1945, the facility was 90% completed and the some machine tools had been installed. Production of U-boats was due to begin within two months.[6]
The pens were attacked by the RAF the 27 March 1945. The attacking force consisted of 20 Avro Lancaster heavy bombers of 617 Squadron which had after the "Dambusters" raid developed precision bombing methods. Simultaneously, a force of 115 Lancasters bombed the nearby fuel oil storage depot. The bombers were escorted by 90 RAF P-51 Mustang fighters of 11 Group[7]
The Lancasters attacking Valentin each carried a single, large earthquake bomb - seven carried a 6-ton Tallboy bomb, and thirteen carried a 10-ton Grand Slam bomb. Two Grand Slams hit the target and penetrated about half-way through the 15-foot (4.6 m) thick ferrous concrete roof before exploding. The explosions blew large holes in the remaining thickness of the roof and brought down around 1,000 tons of debris into the chamber below.[8] Workers who were inside the bunker at the time survived, as the bombs did not penetrate the roof before exploding.[8] Another bomb caused damage to a nearby electricity plant, workshops and concrete mixing plant.
Fortunately for the British, the two bombs struck and penetrated the 4.5-metre (15 ft) thick west section of the roof. Post–war, American analysis suggested the 7-metre (23 ft) thick, east section would have been able to resist even the Grand Slams, although not without significant damage, and it would likely not have resisted repeated hits.[8]
Three days later, on the 30th of March, the US Eighth Air Force attacked Valentin with Disney bombs. These were large (4,500 lb (2,040 kg)) bombs with hard steel casings rocket-assisted to increase their penetrating power. Sixty were launched but only one hit the target, causing little damage.[8] However considerable damage was done to installations surrounding the bunker.
The pens were abandoned. Four weeks after the bombing, the area was occupied by the British Army's XXX Corps, which captured Bremen after a five-day battle.[8]
The prisoners held at the Neuengamme concentration camp and its subcamps were evacuated before the arrival of the British. Many were placed on board the SS Cap Arcona, this German ship was heavily-laden with around 5000 concentration–camp prisoners when she was attacked and sunk by the RAF on May 3, 1945; only 350 prisoners survived.[9]
Further bombing of Valentin occurred post-war. Beginning in March 1946, Project Ruby was a joint, Anglo-American project to investigate the use of penetration bombs against heavily protected, concrete targets; the Valentin pens and bunkers on the German island of Heligoland were selected as targets for the testing. Bombs were carried by Avro Lancasters from No. 15 Squadron RAF and US Boeing B-29 Superfortress and Boeing B-17 Flying Fortress aircraft operating from RAF Marham. Around 140 sorties were flown, testing a range of different bombs.[10]
In 1960, the bunker was taken over by the German Navy, for uses as a storage depot. However, high maintenance costs forced the German Defence Ministry to offer it for sale in 2008.[11]
Military use finally came to an end on 31 December 2010. It is intended to develop the bunker as a memorial and a museum.