Hitler, Donitz, and the Baltic Sea (34 page)

U-3008
(Type XXI U-Boat) at Wilhelmshaven, June 1945. Note the two type IX submarines to its left.
U-3008
was one of only two type XXIs to make a wartime patrol. (Naval Historical Center)

Yet trouble was on the horizon. Dönitz met with Hitler in mid-April 1943 and reported on rising submarine losses in the Atlantic. Germany had lost nineteen U-boats in February, fifteen in March, and six during the first ten days of April. The advent of more effective Allied antisubmarine measures, he declared, called for increased U-boat construction. Dönitz proposed that the goal be increased from the as yet unreached figure of twenty-five submarines monthly to thirty, and Hitler agreed. In May the Germans claimed to have sunk fifty-seven ships of 344,000 tons, but at the cost of thirty-eight U-boats. Dönitz concluded that losses had reached an unacceptable level and ordered his submarines to leave the North Atlantic.
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Twice that month Dönitz briefed Hitler on the crisis of the U-boat war. He explained that Allied air superiority, coupled with a new device that enabled aircraft to locate submarines even during conditions of poor visibility, had deprived the U-boat of its advantages of stealth and surprise. Dönitz insisted that current losses made yet another increase in submarine production necessary and secured Hitler’s consent to raise production to forty U-boats per month. To expedite this, Dönitz asked that the armaments minister, Albert Speer, take over all naval construction, and Hitler approved this measure on 31 May.
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USS
U-3008
(ex-German submarine
U-3008
) at the Portsmouth Naval Shipyard, Kittery, Maine, August 1946. (Naval Historical Center)

USS
U-3008
(ex-German submarine
U-3008
) off Portsmouth Naval Shipyard, August 1946. (Naval Historical Center)

Dönitz planned to regain the initiative in the war at sea with two new models of submarines, the Types XXI and XXIII. The Type XXI, intended for action in the Atlantic, had a crew of fifty-seven, was 237 feet long, weighed 1,600 tons, and could maintain a submerged speed of eighteen knots for and hour and a half, or twelve to fourteen knots for ten hours. This speed and endurance signified a tremendous improvement over existing U-boats, which traveled underwater at six knots for forty-five minutes, at best. Most Allied convoys sailed at speeds of six to nine knots; the new submarines would be able to approach convoys and escape pursuit much more easily. Furthermore, the addition of a “silent running” motor for speeds up to five knots would make detection by listening devices much more difficult. The Type XXI’s design also incorporated additional defensive and offensive improvements. Thicker hull plating rendered the submarines less susceptible to damage from depth charges, and improved listening and location devices permitted submerged attack without the use of the periscope. These U-boats were also called “electro-submarines,” because of their two 2,500-horsepower electric motors.

USS
U-3008
(ex-German submarine
U-3008
) at sea, April 1948. (Naval Historical Center)

The idea for the Type XXI had originated at a conference Dönitz held in Paris in November 1942 with U-boat engineers and representatives from the Naval Construction Office. The designs for these submarines, completed in June 1943, combined the streamlined hull form of the Walter submarine (discussed below) with conventional means of propulsion. With its larger hull the Type XXI had two to three times the battery capacity of existing U-boats, which greatly enhanced its submerged speed and endurance. This submarine could also dive deeper than current U-boats; it was capable of reaching 376 feet, compared to 309 feet for the Type VII-C.
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The Type XXI had six bow torpedo tubes and could fire eighteen of its twenty torpedoes in twenty to thirty minutes.
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The smaller Type XXIII, intended for use off Britain’s coast and in the Mediterranean and Black seas, had a crew of only fourteen, was 114 feet long, weighed about 250
tons, and could cruise underwater at twelve and a half knots for one hour. The Type XXIII’s maximum diving depth was 330 feet. One disadvantage of its small size, upon which Dönitz insisted so it could be transported by rail, was that it carried only two torpedoes.
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In July 1943 Dönitz enthusiastically reported to Hitler that with their ability to approach convoys and evade pursuit at high speed, the new submarines would render current antisubmarine vessels obsolete, because Allied sub chasers were designed to combat U-boats with slow underwater speed. Furthermore, a submerged speed of eighteen to nineteen knots provided an advantage that would persist for quite some time, since the Allies could not increase convoy speeds to much more than ten knots. The electro-submarines had defensive advantages as well. Dönitz explained that the new submarines could dive faster if attacked and quickly pass through dangerous coastal areas en route to and from operating zones. Intensely interested, Hitler queried Dönitz on a number of the new U-boats’ technical aspects and agreed that they signified a revolutionary development. Hitler asked when the first of these submarines would be ready; Dönitz replied that because the Naval Construction Office’s estimate of November 1944 was too late, he had requested Speer, who was present, to devise a method to accelerate production. Hitler turned to Speer and instructed him to give construction of these U-boats top priority.

Dönitz also briefed Hitler on recent developments in the U-boat war. He reported that a professor at IG Farben believed he could develop a material to absorb radar waves. He announced also that he planned to return to the North Atlantic once a new antidestroyer torpedo was ready. Finally, he requested additional manpower for his branch of service; Hitler replied that he was devoted to the navy and would do everything he could for it.
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In hopes of regaining the initiative in the U-boat war, in mid-August Dönitz ordered submarine construction shifted to the new types XXI and XXIII. Despite this changeover, he insisted on a steady monthly output of forty submarines. Speer had reexamined initial delivery estimates and promised the first Type XXI in April 1944. To expedite their availability, Speer built these new submarines in a radically new fashion. His biggest gamble was to rush the submarines into production straight from the design stage, without first building a prototype.
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To ensure a smooth transition to the new building program Speer established a Central Board for Ship Construction in the summer of 1943. This committee consisted of representatives from the navy and the Armaments Ministry; it was headed by Otto Merker, whose previous experience was in the automobile industry. To
reduce the amount of time and the number of workers required to build the U-boats, Merker proposed building the new submarines in prefabricated sections to be fitted together according to assembly-line procedures. Over a thousand designers and engineers worked at a central design agency in Blankenburg, in the Harz Mountains, to draw up the final plans for the new U-boats. Naval Construction Director Heinrich Oelfken headed this organization, the Glückauf Construction Office. Naval engineers concluded that building the Type XXI in eight sections would cut construction time from at least twenty-two months to as little as five to nine months.
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In addition, early estimates revealed that sectional construction would reduce slip time by 50 percent, a matter of vital importance, because submarines were particularly vulnerable to air raids while on slips.
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Industry throughout the Reich produced submarine engines and accessories, and thirty-two inland factories built the prefabricated sections. From these factories the sections, weighing up to 150 tons and thus too heavy for rail transport, proceeded via inland waterways to eleven fitting-out yards near the coast; there they received propellers, engines, periscopes, cables, and other equipment. Finally, the completed sections went to three nearby shipyards—in Danzig, Bremen, and Hamburg—for assembly.
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Dönitz placed orders for 170 Type XXI and 140 Type XXIII U-boats in the fall of 1943.
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The Germans planned to transfer final assembly of the new submarines from vulnerable shipyards to a colossal bombproof plant. Work on this facility, located on the Weser River near Bremen, began in early 1943 and was still in progress at the end of the war. The complex was approximately 1,350 feet long, 380 feet wide, and 75 feet high, with reinforced concrete walls nine to thirteen meters thick and a roof twenty-two feet thick. The building would accommodate twenty-four sections and thirteen or fourteen assembled submarines. The sections were to reach the building on barges traveling up a connecting canal and then to proceed along an assembly line, with finished submarines coming off the line inside the shelter. At the end of the assembly line each U-boat would be launched by flooding a lock chamber. Following engine tests the submarine would leave the plant’s bombproof doors and enter a canal to the river for its journey to the sea. The navy planned the construction of several similar installations.
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Although never completed, the undertaking of this mammoth plant reveals the expenditure of labor and materials the Germans were willing to make to build these U-boats.

Yet even the formidable Type XXIs and XXIIIs represented only an intermediate stage in German submarine development. Dönitz intended
the “electro” U-boats to carry on the fight while the navy perfected a still more advanced weapon, the Walter U-boat. In the early 1930s engineer Hellmuth Walter had devised plans for a high-speed, lightweight submarine with a streamlined shape and an engine that used hydrogen peroxide fuel, which would eliminate altogether the need to surface. In 1939 he received a contract to build an experimental submarine. Walter built an eighty-ton unit, and during its trials in 1940 the Walter U-boat attained an astonishing underwater speed of 28.1 knots. In November 1941 Raeder and Adm. Werner Fuchs, head of the navy’s Construction Office, attended a demonstration of this U-boat. Raeder expressed great interest, though Fuchs’s office was slow to approve further tests. In January 1942 Walter contacted Dönitz, who embraced the idea wholeheartedly and requested development of these submarines as quickly as possible. Yet Fuchs’s office contended that the introduction of a new-type U-boat would impede current production. Dönitz nonetheless continued to push this project, and on 4 January 1943 the navy ordered twenty-four small Walter submarines, designated the Type XVII.
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What Dönitz really wanted, however, was an Atlantic U-boat, and Walter began work on a submarine of this type in January 1942. Still the navy was hesitant to develop Walter submarines. Dönitz sent word to Hitler, who called a conference to discuss the Walter submarine on 28 September 1942. Hitler began the meeting by stressing the significance of quickly bringing new weapons into operation. Dönitz seized this opening and declared that existing U-boats required technical improvements to maintain current levels of success in the face of improved Allied antisubmarine tactics. The advantage of a submarine with high underwater speed lay in its ability to approach convoys quickly and elude pursuit. An increase in diving depth would help U-boats evade sonar detection and reduce damage from depth charges. The Walter U-boat was exactly what he needed. Hitler enthusiastically supported Dönitz, which finally put an end to Fuchs’s foot-dragging. Walter presented the drawings for an Atlantic U-boat, designated Type XVIII, to Dönitz in November. Dönitz demanded that the Type XVIII enter production as soon as possible; Walter pointed out that it would take at least a year. Engine installation posed problems for serial production, current manufacture of hydrogen peroxide was minimal, and his engineers wished to await test results from the smaller Type XVIIs and two prototype Type XVIIIs.
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Hitler expressed keen interest in this project and suggested construction of these U-boats in protected bunkers. By mid-January 1943 Walter had completed revised plans for an Atlantic U-boat. He envisioned the Type XVIII as having a top submerged speed of
twenty-four knots, maintained for 270 nautical miles. By the end of the war seven Type XVIIs had been commissioned, but only as experimental and training submarines; they never saw action. The Type XVIIIs were not completed before Germany’s defeat.
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