Concrete dens of gray wolves
Methods of protecting submarines in bases were more than relevant for the Kriegsmarine: the fact is that the tactics of "wolf packs" provided for the concentration of submarine forces on such a scale that no bases for dispersing submarines would be enough. Consequently, the English could not cover several submarines in the harbor at the same time. aviation had quite high chances. At the end of 1939, German admirals decided to build bunkers for U-boots in open spaces near rivers (to make it easier to organize supplies that were not tied to railways).
Elbe II bunker, top and front view
The first "U-boot-bunkers" - bunkers for submarines, were built in 1940 on the territory of the Reich - in Hamburg "Elbe II" and on Heligoland - "Nordsee III". The bunkers were built by the "Organisation Todt", which had experience in implementing large projects in the form of the autobahn network.
The construction was not easy: the soil in Hamburg is very inconvenient for such structures (silt). Therefore, the bunkers were erected using the caisson method: the foundation of the building was built on piles, for the installation of which it was necessary to wash away the bottom. About 2500 piles with a cross-section of 38x35 cm were used to create one bunker pencil case (of which there were two). Each pile withstood a load of 60 tons, and such strength was not superfluous: the amount of iron reinforcement per cubic meter of fortification concrete was 49 kg. In total, about 50 cubic meters of reinforced concrete were used to build the walls and roof. Very little compared to future bunkers (there, it’s funny to say, the roof was only 000 meters thick!), but a bad beginning is a bad beginning! The bunker was commissioned in March 3 and was used until the end of the War.
Plant-bunker "Valentin"
In addition to the bunker for sheltering submarines, the bunker-factory "Valentin" was built near Hamburg, in Farge, on the Weser River. About 10 thousand concentration camp prisoners and prisoners of war were involved in the construction of the plant. 6 thousand of them died from hard work and insufficient nutrition. The famous submarines of the XXI series were built (or rather assembled from sections delivered along the Weser) at the plant.
The tubes deserve a separate mention. All U-boot bunkers were divided into separate "tubes" - separate docks 80-90 meters long and 10-17 meters wide. One tube could service 2 to 4 submarines at a time. The tubes were separated by thick supporting walls that supported a bomb-proof roof. Even if a bomb penetrated the roof, only one tube was damaged, while the neighboring ones remained unharmed. In large bunkers, one or more tubes could act as a dry dock.
The roofs of the first Hamburg bunkers were used for camouflage, as models of administrative and office buildings, but later the roofs were more often used to house anti-aircraft gun batteries. The front of the bunkers was locked with massive gates, and the rear part of the bunker was occupied by storage facilities, repair shops with a wide range of machines and equipment, and railway tracks were also connected here, along which everything necessary for repairs, servicing of submarines and supplies necessary for a long voyage were delivered.
Villa Kernevel - "Papa Dönitz" loved to fight in comfort!
But the construction of bunkers for submarines reached its peak in 1941, after the capture of France and Norway. The Atlantic coast of these countries was much more convenient for the "wolves of Dönitz" in terms of access to the Atlantic. The vice-admiral organized his headquarters in Lorient, in the villa Kernevel. Accordingly, the largest number of bunkers was built in Lorient - six pieces! The 2nd and 10th submarine flotillas were based in them.
There is only one bunker in Brest, but it is big!
There was only one bunker built in Brest, but it was the largest! It had 15 compartments, in which the 1st and 9th submarine flotillas were based. The dimensions of the gigantic structure were 300x175x18 meters, the thickness of the supporting walls was 1-2 meters, the thickness of the roof was initially 4,2 meters, but later increased to 6,1 meters. Small bunkers for anti-aircraft guns were located at the corners of the bunker's roof. The construction of the building took 500 days and was completed in 1942. And already on September 4, 1944, the last submarine left here - U-256: Allied troops were approaching Brest, and the structure was abandoned ...
Bunker in Saint-Nazaire
A slightly smaller bunker was built in Saint-Nazaire, with 14 penstocks, where the boats of the 6th and 7th flotillas were based. Of its 14 penstocks, 8 could serve as dry docks. The bunker was 300 meters long, 130 meters wide and 18 meters high. Between penstocks 5-6 and 12-13 there are passages providing access to the upper levels of the bunker, where 62 workshops, 92 dormitories for submarine crews, 150 utility rooms, 20 pumps, 4 kitchens, 2 bakeries, 2 power plants, a restaurant (the "Dönitz wolves" loved to serve in comfort!) and a hospital were located. The submarine base in Saint-Nazaire was declared a "festung" by Hitler, so the garrison under the command of Lieutenant General Junck held out until May 8, 1945, and only after learning of the capitulation of the Reich did it resign. weapon.
Construction of a bunker in La Rochelle
The 3rd flotilla of U-boots was based in La Rochelle, and of course, a bunker was also built here! Although, it was relatively small: 192x165x19 meters, 10 cases, a roof 7 meters thick (or more precisely, 3,5+3,5 meters: an air gap was made between the layers of concrete for greater overall stability of the structure). But everyone knows it: it was here that the famous film "Das Boot" was filmed with Jurgen Prochnow in the leading role. And "Indiana Jones and the Raiders of the Lost Ark" - too, only in this film epic there are terrible inconsistencies with the chronology: the War had not yet begun, and the bunkers had already been built, but that's not why they are loved! 425 thousand cubic meters of concrete were used to build the bunker: is it clear why I wrote that 50 thousand cubic meters of the Elbe II bunker in Hamburg is funny? The bunker was built by 2143 workers from the Todt organization, working day and night, so that in 1943 the bunker was put into operation.
Bordeaux - Italo-German bunker BETASOM
The fifth point, on the territory of occupied France, where a bunker for submarines was built, was Bordeaux. This structure even received its own name: BETASOM. The fact is that the flotilla of Italian submarines allied to the Germans was initially based here, so the bunker was named after the first letters of the Italian words "Bordeaux" and "Submarine" ("Sоmmergibile"). The bunker was 245 meters long, 162 meters wide and 19 meters high. The Italians went out to sea from Bordeaux until 1943, when Italy left the war and the bunker was occupied by the Germans.
Trondheim - Bunker "Dora-1" in its current state
In addition to France, the Germans also built a bunker for submarines in Norway, in Trondheim. However, they built far more than just a bunker: Hitler had big plans to populate Norway with Germans, so Albert Speer built an entire Nazi city here — Nordstern (Northern Star, indeed!). 300 thousand German "colonists" came from Germany: the project was supported by both Karl Dönitz and Erich Raeder: not only submarines, but also the battleship Tirpitz were to be based and repaired here.
The bunker was named "Dora-1". Why such a name? Well, it was built by prisoners from the "Dora" concentration camp. The bunker measured 153x105 meters, with a 3,5 meter thick concrete roof. According to the design, the bunker was supposed to be two-story: the second floor, as usual, would house workshops, crew quarters, warehouses, and all that stuff. But... the Norwegians were in no hurry to help the Germans, but they tried their best to hinder them. It was not possible to obtain local building materials: almost everything down to the last nail had to be brought from Germany. That is why the second floor did not work out. The construction of the "Dora-2" bunker was not completed for the same reason, and the construction of "Dora-3" was abandoned altogether.
The Grand Slam Bomb is the only antidote to U-boot bunkers.
How should we evaluate the construction of bunkers for submarines by the Third Reich? Definitely, as a very successful decision! The Allies knew from the very beginning what kind of structures these were, but they could do nothing with them until the end of the War. Regular bombs could not penetrate their concrete roofs, and special concrete-piercing bombs "Tallboy" and "Grand Slam" appeared only towards the end of the War. Therefore, the only bunkers hit by Allied aircraft were the bunker-factory "Valentin" in Farge and the bunker in Hamburg, which were hit by two "Grand Slams". But this happened already in March 1945, when such operations could, by and large, not be bothered...
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