Construction of the Type XXI submarines

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During World War II planned the High Command of the Navy under its new commander Karl Doenitz , the former commander of submarines , from mid-1943 the production and use of a large number of new submarines of type XXI (type 21) to a should lead to another turning point in the submarine war . The previous submarine types with low underwater speed and range were no longer able to cope with this due to new technologies and increased defenses.

planning

With the new submarines, the previous underwater speed should be more than doubled, the underwater range increased by a factor of about 8 at the same speed and the diving depth increased by about 30%. The previously separate and mostly individual orders for naval armament were transferred to the Reich Ministry for Armaments and Ammunition , headed by Albert Speer , on June 10, 1943 with the consent of Adolf Hitler . Speer entrusted the General Director of Magiruswerke , Otto Merker, with the management of the new Main Shipbuilding Committee (HAS) . After a short time he presented a plan for the series production of the submarine class XXI based on the model of car production using the clock and section method, which at the time seemed sensational , in order to shorten the construction time of the new submarines.

The construction time has been reduced from seven to three months. As early as December 8, 1943, the 1020-strong central design office "Ingenieur-Büro Glückauf" (IBG) in Blankenburg (Harz) reported the completion of the design and manufacturing drawings . In order to save time, a prototype was not built, which would not have been expected to be completed until October 1944. The proposal by Admiral Werner Fuchs (1891–1976) to have the finished construction checked by the K Office was also rejected because of the time required for this, of three to four weeks. Instead, series production began immediately . Occurring problems should be resolved after the delivery of the first submarines, which were intended for testing and training. Two months instead of the previous five months were planned for the steel construction, and four instead of ten months for the section construction. The planned total construction time was nine months instead of at least 22 months. For this purpose, the working hours have been increased to 72 hours per week and more.

From autumn 1944, 33 submarines were to be delivered per month, which should be ready for use from the beginning of 1945, and later 38 submarines. For this purpose, all ongoing construction contracts for the new Type VII C / 42 submarine were canceled . The planned final assembly of the Type XXI took place from nine individual sections in the following shipyards :

Each section should be able to be equipped by at least two shipyards so that the entire production would not have to be stopped in the event of a failure. Equipment yards for the sections were:

The raw sections intended for assembly should also be delivered from inland by inland waterway so that the resources available there can be used. For each individual section, four production sites were planned, distributed across the Reich , in order to avoid targeted air attacks on individual production sites through decentralization. Due to strict secrecy, this goal was largely achieved. The following companies were intended to be the manufacturers of the raw sections:

The powerful new e-machines were mainly supplied by SSW from the Dynamowerk Berlin , Vienna- Leopoldau and Nuremberg , AEG from the Brunnenstrasse plant in Berlin and, as a license, in small numbers from BBC and Garbe, Lahmeyer & Co. The total of 236 tons per submarine Batteries came from AFA plants .

War economic effects

At that time, series production was a major burden for the German armaments industry , including raw materials such as steel , rubber , lead and copper , which led to severe restrictions in many other important areas. On February 22, 1944, OBaurat Waas of the shipbuilding commission stated that the lack of lead would only allow the Type XXI to be continued until summer 1945. On September 14, 1944, however, this was corrected by the chairman of the shipbuilding commission, Vice Admiral Karl Topp , to “lead supply secured well into 1946”.

The monthly steel quota promised to the Navy was increased from around 120,000 tons to 165,000 tons. However, with the inclusion of foreign steelworks, this was more than offset by total production that rose to a record 3,173,000 tons in March 1944. Within the program, 135 steel construction companies and thus almost 50% of all German structural steelwork were involved in the manufacture of the raw sections and their assembly.

The planned working hours per submarine for steel construction and shipyard amounted to 266,000 hours, the pure construction costs were to be 4.6 million Reichsmarks . For comparison: the hourly wages customary for workers after deducting social security contributions ranged between 70 pfennigs and one Reichsmark, the annual salary of a skilled worker could reach 2000 Reichsmarks. With the program and the construction of the smaller submarine class XXIII , almost all resources available for building new warships were concentrated on the construction of submarines and surface units for submarine warfare. The construction of other warships above destroyer size , such as that of the aircraft carrier Graf Zeppelin , was completely stopped. The orders to build 162 submarines of other types, including 18 Walter submarines, were also canceled on September 30, 1943. The submarine construction now concentrated on the two types XXI and XXIII, 28 Walter submarines of the small type XVII and two test structures of the larger submarine class XVIII . All workers involved in the construction of submarines, their weapons and surface units serving submarine warfare were exempted from conscription to the army by a protective decree signed by Adolf Hitler on February 8, 1943 .

A large part of the entire German electrical industry was claimed for the Type XXI. From December 1943 to December 1944, the monthly number of productive hours worked in German shipyards in new submarines rose from around 4.2 to around 8.4 million. With weekly working hours generally increased from 48 to 60 hours without vacation from September 1944, this would correspond to a number of 32,000 shipyard workers. Forced laborers and those employed in war-related companies often had longer working hours of up to 80 hours a week, so that with sufficient certainty it can only be assumed that at least 25,000 shipyard workers were employed.

The Schichau shipyard in Danzig had 7650 employees on June 1, 1944 , but only 1551 skilled workers . The remaining employees were semi-skilled or unskilled workers, including around 1200 women and unproductive directors, a total of 2888 foreigners , 1266 prisoners of war and Italian military internees, and 430 German camp inmates, presumably from the Stutthof concentration camp . Some Jews were also employed in building submarines.

The shipyard workers mainly worked for the Type XXI and the much smaller Type XXIII; of other new submarines with Walter drives , only three were ultimately put into service. Added to this was the increase in the proportion of domestic suppliers due to the sectional construction . The ratio between material costs (diesel engines, electrical systems, small parts) and wage costs in a shipyard was around 20/1. By the end of December 1944, a total of 232,000 tons of steel had been delivered for the Type XXI, 1.27% of the German annual production in 1944. The working hours of the shipyards and the number of submarines delivered were concentrated in the narrow period of September to December 1944. For expansion and New construction of the submarine bunkers in the German Reich was planned for another 95,000 tons of steel in December 1942.

Protective structures

Since the German Air Force , Flakhelfer , HJ-Marinehelfer , Flak and Flaktürme were no longer able to adequately protect the production facilities on the territory of the German Reich from the effects of the aerial warfare with bombers of the Royal Air Force and the United States Army Air Forces , the final assembly and Repair of the submarine class XXI to be relocated to large submarine bunkers . In the previous course of the war, these had mostly offered adequate protection from all types of bombs . Some of the bunkers were already there, such as the submarine bunkers Kilian and Konrad in Kiel , the Elbe II and Fink II bunkers in Hamburg and the Wenzel bunker in Wedel . Others like the largest submarine bunker Valentin, which cost 120 million Reichsmarks (length 450 meters, width 100 meters, ceiling thickness 7.3 meters, protection for 24 individual sections and 13 complete submarines), the construction of which began in 1943 and on which At times up to 15,000 workers worked, or the submarine bunker Hornisse in Bremen was specially built for the Type XXI. At the end of the war, the Valentin bunker was 80% complete.

The thickness of the concrete ceilings of these bunkers was between three and seven meters, the side walls were somewhat weaker. In the last months of the war, however, it became clear that specially trained and equipped British bomber groups with new, superheavy bombs of the Tallboy type and especially Grand Slam were able to break through the ceilings of the bunkers or to crush the side walls. The tremendous detonation wave of the Grand Slam, which struck at supersonic speed from an altitude of 6,700 meters, caused earthquake-like tremors.

Forced labor

Thousands of forced laborers , prisoners of war and concentration camp inmates were used to build the bunkers, and 10,000 to 12,000 forced laborers from occupied areas and the Bahrsplate concentration camp were used to build the Valentin submarine bunker . Only 1,700 deaths are registered because the Polish and Russian deaths were not taken into account. Prisoners from Neuengamme concentration camp were used to build the Hornisse submarine bunker .

Up to 1,500 prisoners from the Hanover-Stöcken concentration camp (battery works) were used to produce the large batteries required for the XXI, and they were housed in a camp complex on the premises of the AFA Hannover-Stöcken branch. In addition, there were 3700 forced laborers and 1300 German workers and employees, a share of 25%. In the AFA main plant in Hagen , however, no concentration camp prisoners were used. In addition to the construction work to complete and expand the camp, the prisoners worked in the accumulator factories in the production of the large submarine batteries. This included the lead foundry, where the inmates had to pour the lead plates for the battery cells without protective clothing or protective masks . They inhaled the toxic fumes of the warm lead mass while the German workers wore protective masks. Many prisoners suffered lead colic , also because malnutrition leads to a significantly higher sensitivity to lead poisoning. Other jobs were the acid department and the hot counter rollers. A lack of occupational safety also led to accidents and damage to health. There is evidence that 403 concentration camp prisoners from sticks were buried in the Seelhorst cemetery. An unknown number of prisoners were transported back to the Neuengamme concentration camp, where they mostly died of illness and weakness. There were seldom assaults in the factory, while in the concentration camp if the workload was too low, they were beaten with wooden sticks and dogs were chased at people. Prisoners were kicked in the abdomen by a mentally ill person, which often resulted in death, or they were splashed with water in winter. They received only half the minimum food necessary for heavy workers to survive. There were eight documented escape attempts, all of which were fatal. There was a gallows in the concentration camp that could be seen from outside the camp. It has been used at least twice for its intended purpose.

In the course of an evacuation in accordance with the instruction not to leave any forced laborers to the enemy, the prisoners who were able to march left the Stöcken subcamp on foot in the night of April 6th, 1945 in the direction of Bergen-Belsen , where they arrived on April 8th. SS guards shot prisoners who could not keep up. On April 8, the sick prisoners were transported away from sticks by train. The train reached Mieste via Fallersleben and Wolfsburg , from where the prisoners marched on to Gardelegen . On April 13, they were taken to a field barn with a large group of inmates from the Mittelbau-Dora concentration camp , which was then set on fire. The following day men of the Volkssturm tried to bury the bodies. On April 14, 1945, US soldiers reached Gardelegen and discovered the mass murder the next day. 1016 deaths were counted.

From 1944, prisoners from the Mauthausen concentration camp and the Floridsdorf subcamp were also deployed in the new AFA branch in Vienna - Floridsdorf to produce battery cells of the type 62 Z AFA 44 MAL 740 W and E. The approximately 7,000 employees of the large and modern AFA-Werkes in Poznan were mostly forced laborers who were subject to particularly strict rules of conduct.

Production numbers

The first completed boat U 3501 was made floating with wooden wedges at Schichau in Danzig because of the launch one day before Hitler's 55th birthday and launched on April 19, 1944 as the “Führer birthday boat ”. It had to be towed back into the dock immediately. Instead of functioning fittings, the built-in sections often contained dummies. Nevertheless, congratulatory telegrams met u. a. medals were awarded by Adolf Hitler to those responsible for the launch. The directors of the other shipyards had refused to launch unfinished boats. Due to deadlines, the sections were only delivered to the assembly yards in a 50-80% finished state. The result of the hasty launching was rework, which delayed the commissioning of U 3501 (without flak towers, later used as a school boat and after a bomb hit as a power generator) until July 29, 1944. When General Director Franz Stapelfeldt from Bremer Deschimag repeatedly pointed out the unrealistic deadline demands, he was relieved of his post.

The submarines were delivered with a three-month delay from July 1944. By the end of 1944, 61 type XXI boats had been delivered, all with technical defects and not ready for action. Originally a delivery of 233 submarines was planned for this date. The monthly production, however, approached the original plan with 28 submarines. However, it fell sharply in the following months because the onset of winter blocked waterways, important suppliers were occupied, the railroad lines and the canal routes for inland navigation in the German Reich were largely interrupted or destroyed and the shipyards in the east were occupied.

The high time pressure, strict secrecy, bottlenecks in the available raw materials and the too late allocation of experienced engineers from the front to the central design office "Ingenieur-Büro Glückauf" (IBG) in Blankenburg (Harz) resulted in numerous deficiencies in the U. -Boats, which came to light during the subsequent tests and required extensive changes and rework. The IBG's catalog of changes up to September 1944 totaled 150 construction changes. In addition, due to delivery problems, not all of the planned equipment and devices could be installed in every submarine. One part could only be used as a school or test boat.

The head of the Office for Warship Building, Vice Admiral Friedrich Ruge , noted in his diary from August 4, 1944 to May 26, 1945 with the date August 9, 1944: “The question of responsibility for section building has still not been clarified, deadline pressure too strong. Sections never finished, fittings sometimes only 45%. With the date March 9, 1945, he noted that the sheet metal was too thin due to a design error : “In any case, the immersion depth is hardly better than with Type VII C. ”.

Admiral Werner Fuchs initially refused to accept the boats classified as unusable at the front. According to his later assessment, the first XXIer boat would be suitable for front use from May 1945.

On September 11, 1944, the US Army had reached the western border of the Reich and immediately threatened the Ruhr area after the Battle of Aachen . This threat was to be eliminated by the Battle of the Bulge (December 16, 1944 to early 1945). The focus of arms production was shifted to land forces (guns and tanks). The promised quantities of steel were not delivered in full. On January 12, 1945, troops of the US Army captured around 20 Type XXI stern sections in a shipyard in Strasbourg on the Upper Rhine , which could not be replaced. There was also a lack of electrical energy due to the lack of coal transports . Due to a lack of electricity in the AFA plant in Hanover (from November 1944), Allied air raids on the AFA plants in Hagen (December 2, 1944) and Vienna-Floridsdorf (March 12, 1945) as well as the failure of the AFA plant in Posen as a result of the end of January 1945 The Battle of Poznan was missing a third of the batteries required for the Type XXI.

The naval armament was converted to an emergency program in February 1945, in which the repair of existing units and the further construction of units that were about to be completed had absolute priority. The "shipbuilding emergency program" of February 20, 1945 still envisaged the construction of 66 type XXI submarines and 21 of the small sister type XXIII. This emergency program could no longer be implemented either. On March 21, 1945, the Schichau Works and Danzig Shipyard were under artillery fire. On March 24, 1945, orders for Type XXI submarines that had not yet started were canceled. Work was only continued on almost finished submarines. On March 27, 1945, the Red Army invaded the Danzig Schichau shipyard. In addition to the submarines U 3535 to U 3542 lying on the Helgen , she also captured a total of 88 individual sections for the Type XXI.

The last type XXI submarine was U 3051 launched by AG Weser on April 20, 1945, seven days before Bremen was occupied by British troops .

commitment

The first submarines were only used at the front in the last days of the war due to delays in the training of the crews due to mines in the training rooms in the Baltic Sea, a lack of fuel and a large number of technical problems. Several were destroyed or sunk in air raids on ports or in the shallow waters of the Baltic Sea, where diving was sometimes not possible. The few submarines that had reached deeper waters were no longer able to attack Allied ships.

literature

Web sources

Individual evidence

  1. ↑ Eberhard Rössler: The fast submarines from Hellmuth Walter . Bernard & Graefe in the Mönch Verlagsgesellschaft mbH, Bonn 2010, ISBN 978-3-7637-6285-9 (Chapter 7. Unsuccessful efforts for the most modern submarine: The Walter-Type XXVI, pages 99, 105).
  2. ↑ Dieter Hardwig: Admiral Karl Doenitz. Legend and reality . Ferdinand Schöningh, Paderborn 2010, ISBN 3-7637-5186-6 (index of footnotes VIII, The Illusion of the »FINAL VICTORY« WITH NEW BOATS, page 343, points 10 & 31).