In the fall of 1943, Dönitz ordered 152 Type XXI and 140 Type XXIII sub marines. Speer examined the plans and he promised the first Type XXI would be ready in April 1944. Speer determined that the need for early availability of the submarines ruled out the luxury of making a prototype. This later resulted in a number of problems. Speer had established a Central Board for Ship Construction with representatives from both the navy and the Armaments Ministry. He selected Otto Merker (1899–1986), a man from the automobile industry to head the board. To reduce the construction time, Merker proposed a modular approach. Naval engineers estimated that this would reduce construction time from about 22 months to 5–9 months. It would also halve the time submarines were in slips, greatly reducing the time they would be vulnerable to Allied bombing. Merker’s decision on modular construction may have been influenced by the American building of Liberty Ships.
A great number of industrial sites were involved in this mammoth project. Each hull consisted of eight prefabricated sections with final assembly at the shipyards. Some of these sections weighed as much as 150 tons and were too heavy for the rail system. Consequently, they were shipped via rivers and canals to the final assembly yards in Danzig, Bremen, and Hamburg. The Germans planned eventually to transfer all assembly operations to a gigantic bomb-hardened assembly plant at the Valentin submarine pens in the small port of Farge downriver from Bremen. Work on this enormous facility began in early 1943. The plant was nearly complete in March 1945 when it was severely damaged in an Allied air raid using bunker-buster bombs. It was still not completed when the war ended.
Although Dönitz had expected 152 XXIs and 140 XXIIIs to be completed by the end of October 1944, the completion schedule could not be followed for a variety of reasons as detailed below. Only 118 Type XXI were completed by the end of the war and only four of these were ready for combat. Only 59 Type XXIIIs of the 140 planned for were ready by the end of the war and only six put to sea, the first on 29 January 1945 and the last on 4 May. None was sunk while engaged in operations.
There are those who claim that the new boats should have been given a higher priority in armament production. They forget the fact that Hitler was caught in a “Catch 22” situation. If he reduced the priority accorded the Luftwaffe, the facilities needed for submarine construction and the synthetic oil refineries would have been destroyed earlier than was the case. If he reduced the priority for the army, replacements for the hard-pressed units in both the East and West would quickly slow down, as would equipment for the new divisions that were being formed. Lowering the priorities for the other two services could only lead to undesirable situations and a shortening of the war. Professor Grier provides some interesting and telling figures in this regard. He notes that the steel required for the Type XXI submarines “would have provided Guderian 5,100 additional tanks” and that another ‘miracle weapon’ program, the V-2 rockets “devoured resources equivalent to 24,000 combat aircraft.” He concludes that “the German war effort certainly would have benefited more from five thousand tanks than from Dönitz’ ‘miracle weapon.’”
A possible solution to the problem was to withdraw units that were ordered to defend the “fortified places” to shorter defensive lines. The wisdom of some decisions can only be judged retrospectively. This was not the case with allowing large forces to be voluntarily encircled or besieged without realistic prospects for relief or re-supply. History tells us that this is a virtually certain prescription for disaster. The new submarine program, on the other hand, cannot be judged realistically except in retrospect.
The lack of prototypes for the new submarines and the fact that many companies involved in the modular construction had little experience in shipbuilding caused severe problems. Much time was wasted because the modular sections did not interlock properly because specific tolerances were exceeded. Additional delays were caused by the long training time required for crews. Most sources note that the normal submarine training time was about three months, but the new types, because of their advanced technology and design complexity, required around six months. The Allies had also started—on August 7, 1944—heavy aerial mining of the Bay of Danzig, now the primary German training area. The mining forced the Germans to move their training to the less suitable Bay of Lübeck. A number of new submarines that were near the completion of trials and ready to head to Norway for stationing were lost in the Bay of Lübeck, probably victims of mines. The loss statistics of Claes-Göran Wetterholm undoubtedly include those lost in routine training accidents.
Allied bombing of production and assembly facilities became an increasing problem for German submarine output. Except for the mining operations in the Baltic, the Allies did not make a concerted effort to damage and destroy the German submarine facilities until January 1945. This objective was simply not on the priority list of the strategic air offensive. Instead, the priorities of the Allied heavy bomber forces were:
- Synthetic oil facilities
- Transportation network
- Tank and mechanized transport production facilities.
The British Admiralty was aware, however, that the Germans were developing new submarines. Intelligence was collected not only through an analysis of Enigma deciphers but by reconnaissance flights over German harbors. By mid-December the National Intelligence Division had come up with a rather accurate estimate and status of the new German submarine production. They estimated that 95 Type XXIs were under construction or in various stages of preparation and that 35 had already been commissioned. The Enigma deciphering even allowed the British to conclude that the commanders appointed to skipper these submarines were experienced and capable.
From their information on the German submarine program, the Allies were less worried about the existing submarines being fitted with snorkel and the Type XXIII than they were about the ocean-going Type XXI. The Allies felt that they could handle the threat from the snorkel and Type XXIII submarines by using existing anti-submarine warfare assets to the maximum. However, they felt that the Type XXI could seriously impede transport across the Atlantic and threaten landing operations if those submarines were deployed in sufficient numbers. Only a dramatic increase in anti-submarine warfare assets could counter this possibility. The alarming intelligence reports caused the Admiralty to urge a heavy bombing campaign against submarine production facilities and slips.
The Royal Air Force, which was somewhat skeptical about the navy’s intelligence, concluded that an aerial campaign of the kind that was suggested by the Admiralty had to be on such a large scale that it would constitute a serious detraction from existing priorities. They noted that German armored forces and the Luftwaffe were seriously constrained by lack of fuel and that any relaxation on existing priorities would lead to the resurgence of the Luftwaffe and allow the Germans to increase their operations vastly on all fronts. The German coal and oil supplies had, by January 1945, been cut to a fraction of what was needed to prosecute the war on two fronts. Therefore, they argued, there should be no shift in priorities until it was shown that the naval commands could no longer cope with the threat.
In the end, the Admiralty convinced the Combined Chiefs of Staff in mid-December 1944 that it was necessary to take the requested action as long as it did not imperil existing priorities. Heavy Allied bombers were ordered to carry out secondary strikes against submarine facilities. Below is a listing of major raids carried out against the submarine facilities and a summary of their results:
- 18/19 December 1944—a “target of opportunity” raid by 227 Lancaster bombers dropped 817 tons of bombs on Gdynia, a port on the west side of Danzig Bay. The bombs sunk two submarine depot ships, a torpedo boat, and five merchant ships. An oil refinery ship, the World War I battleship Schleswig Holstein, and a Type XXI—about to undertake the final training exercise in the Gulf of Danzig—were heavily damaged.
- The first attack by the US Eighth Air Force was carried out on December 31, 1944, when 324 bombers attacked Hamburg, dropping 740 tons of bombs. The Germans shot down 24 aircraft. The raid resulted in the destruction of four Type XXI submarines while seriously damaging two others. A large depot ship and several other vessels were also destroyed.
- An attack on the canals through which pre-fabricated sections were brought to the assembly yards was carried out on January 1, 1945, resulting in the Dortmund–Ems and Mittelland Canals being put out of service until February 6.
- A very successful raid was carried out by the Eighth Air Force against the submarine assembly yard at Hamburg on January 17. The results of the 360 tons of bombs dropped were impressive. Three commissioned Type XXI were destroyed and nine others were seriously damaged. Five merchant ships were also sunk and three damaged. The US lost three aircraft.
- Precision bombing by small groups of Mosquitoes, each carrying a 4,000lb bomb, was carried out against a Type XXI yard in Bremen. These attacks were carried out nightly from February 17 until the end of the month. The most successful attack was carried out on February 21/22. Two Type XXIs were damaged and the launch of three others blocked by debris.
- Eighth Air Force carried out a 198-aircraft raid on the yards at Bremen on February 24. While only one Type XXI was sunk, two floating cranes and the crane used for preparing the submarine were badly damaged.
- An unusually heavy attack by 407 bombers of the Eighth Air Force was carried out on March 11 against the Bremen yard. This attack was so damaging that it virtually shut down the yard.
- A damaging raid on the canal system in February again made it unusable. Another raid on the canal system on March 3-4 damaged it beyond repair.
- Three devastating raids were carried out against the facilities in Hamburg—two by the Royal Air Force and three by the Eighth Air Force. The facilities were virtually brought to a standstill. Eleven older submarines were sunk and five Type XXI were dam aged beyond repair. A new destroyer and 15 other ships were also sunk.
- Two destructive attacks were carried out in late March on the gigantic submarine pen at Farge, near Bremen. One raid was carried out by the Royal Air Force while the other was delivered by the Eighth Air Force. The damage delayed construction.
- Heavy raids were carried out by the Eighth Air Force in April 1945 on the port facilities at Kiel. A total of 1,184 aircraft dropped 3,138 tons of bombs. Three older submarines, two liners, and 10 other ships were sunk.
- The British were also busy over Kiel. On the night of April 8–9, 427 bombers dropped 1,503 tons of bombs. Five commissioned Type XXI submarines and five merchant vessels were sunk. Nightly raids by Mosquitoes were carried out from 21 to 27 April.
- Kiel was attacked again on the night of 14–15 April by 467 British bombers. Seven older and two Type XXI submarines were sunk in the British raids and the facilities were practically destroyed in the combined raids.
Raids not directly linked to the air campaign against the new submarine facilities were also damaging. For example, the bombing of factories in Hanover and Hagen destroyed the production plants for batteries. The only other plant producing batteries for the submarines was at Posen and it was captured by the Soviets in January 1945. The Soviet advance also stopped all work at the submarine assembly yard at Danzig. Churchill writes that the Soviet capture of Danzig, one of the three principal submarine bases, was a great relief to the British Admiralty. He observed that the resumption of the submarine war on the scale envisioned was clearly impossible.
The production of the smaller Type XXIII was not nearly as affected by Allied bombing as the Type XXI. Only five of these boats were destroyed by bombing. There were two reasons for this lesser damage. First, the assembly site in Hamburg was sheltered in hardened concrete bunkers. Second, the other assembly point in Kiel was not heavily damaged by bombing. However, the output of these boats dropped off because the supply parts dried up. The production dropped from nine boats each month in 1944 to four in February 1945.
Dönitz, with his single-minded focus on the submarine war, was probably one of the very few among the senior German leaders who still believed in early 1945 that the war could be turned around. He was repeatedly forced to explain to Hitler why the 1943 production schedule was continually falling behind. In these “excuse” sessions he always maintained that the turning of the tide was just around the corner, when he knew that was not the case. Hitler would not have tolerated this from his generals, but Dönitz had apparently ingratiated himself to Hitler in such a way that it was tolerated. His optimistic approach to a person who faced disasters on all fronts may be one explanation. Their ideological compatibility was undoubtedly also important. Raeder, Dönitz’ predecessor, met with Hitler infrequently, but Dönitz became practically a fixture at Hitler’s briefings and conferences.
Dönitz had focused his entire naval strategy during the last two years of the war on the deployment of the new submarines. While the Germans came up with a design that profoundly influenced future submarine designs, their immense efforts did not help them turn the tide in World War II. The most promising new boats—Type XXIs—never launched a single torpedo at an enemy.