Germany’s geographical position has always placed her at a disadvantage in maritime and naval activity in a war with Great Britain. As demonstrated in both world wars, the Germans could not operate surface ships in the narrow sea lanes around England and through which such ships had inevitably to pass on their route from German ports to the open ocean, or vice versa. German commerce was swept from the seas and Germany placed under British remote blockade. The development of the submarine, however, gave Germany an excellent weapon for a counterattack to offset the British blockade. The result was that during both wars German naval leaders finally put primary emphasis on the U-boat and the war against shipping. The ensuing race between the amount of the enemy’s commerce tonnage sunk and his replacement tonnage construction made it necessary to increase the small number of submarines in commission at the outbreak of hostilities and to maintain, despite all losses, a respectable level of units in operation. As a result, U-boat construction occupied an important place in the work of German shipyards, as well as in the steel plants, and particularly in the German heavy motor and electrical industries.
During World War I, the German U-boat, up to this time completely untried in battle, was developed into Germany’s most powerful naval weapon. At the outset of the war, U-boats were deployed principally for attack on enemy warships, and only subsequent developments during the course of the war made apparent the advantages to be gained by raiding the enemy’s commercial shipping. Hampered by diplomatic protests and considerations for neutral shipping, particularly those of the United States, the U-boat was not turned loose against enemy shipping until the spring of 1917. With the initiation of unrestricted submarine warfare, the German command then hoped to compel the enemy to surrender before the end of the year. Although the sinkings reached the established quota, and the German U-boats had control of the sea making England’s situation critical, the goal of the German command was never attained, because the enemy developed effective counter measures against them, in particular the convoy system, and also because of the great increases in new construction. The United States, which up to 1915 with its annual output of 200,000 tons, had played no significant role in world ship construction, increased its construction capacity so phenomenally that its annual production reached 820,000 tons in 1917, and 2,600, 000 tons in 1918. Thus by the spring of 1918, Allied construction of cargo vessels began to catch up with the tonnage of vessels sunk. In all, the U-boats sank some 18,700, 000 gross tons of commercial shipping during World War I.
Corresponding to the vacillating policy in waging submarine warfare at the time was the fact that submarine construction was not initially conceived as a major factor in the conduct of the war. At the outset, in 1914, Germany had 29 U-boats, twenty of which were first line operational craft. When unrestricted submarine warfare was initiated in February, 1917, after two-and-a-half years of war, there were only 111 submarines in action. Orders for new submarines followed quite irregularly, the controlling factor being contemporary demands from the Front. Because of the rapid evolution of new types, there was no construction plan, so that there could be no planned and efficient use of shipyard facilities. Even the first order for 58 submarines in May, 1916, was not fully completed because the Army high command, as late as June, 1918, had not released technical workers from Army service in order to support the U-boat construction program. The productive power of German industry as late as the end of the war can be revealed by the Scheer Program, set up on October 1, 1918, with the cooperation of industry, which called for 69,000 technical workers provided by the Supreme Command, to make regular deliveries of 33 submarines per month. This program was never put into effect, but it does show what means could have been provided for the conduct of U-boat warfare with efficient and purposeful management. Of a total of 343 submarines placed in service in World War I, 199 units were lost. The number of operational units, not counting training craft and those undergoing trials, during the last year of the war averaged 128.
Submarine Construction Between the World Wars
The successes attained by the submarine make it understandable why the construction and operation of U-boats was forbidden by the Versailles Treaty. Only on June 18, 1935, did the Anglo-German naval treaty make it possible for Germany to resume submarine construction. This international agreement, which represented for Germany the first relaxation of the Versailles Treaty naval limitations, implied at the same time renunciation of any German naval rivalry with England. The future strength of the German Navy both in its overall tonnage and in the single ship categories was limited to 35% of the British totals. A special ruling affecting the U-boat category permitted the eventual construction within the overall fleet strength of a submarine fleet up to 45% of the British tonnage in this type. Over and above this, there was even the possibility under special conditions and after friendly discussion between the two powers of raising the German U-boat tonnage to parity with the British. The limits set by this treaty were not exceeded by the German Navy until the beginning of the war. It is true the German Navy had the same number of submarines as the British at the outbreak of the war, but the German craft were considerably smaller, so that their total tonnage at no time reached the 45% limit.
Experience in submarine construction had not been entirely lost. During the years between 1918 and 1935, German engineers acquired practical experience through participation and cooperation with the Dutch and the Spanish on certain submarine designing and construction projects. The reconstruction of the German U-boat fleet began in 1935 with the building of small submarines of the 250-ton type. The British noted with displeasure that a number of submarines—numerically unimportant, to be sure—were launched very soon after the conclusion of the Anglo-German Treaty. The prefabricated sections of these submarines had been prepared during the course of the Conference, so that assembly of the U-boats was swiftly completed.
After the completion of the first units of this small type (Class II-A and Class II-B) and of a type twice as large (VII), there was a pause in the further development of these types. In 1937 only a single submarine was delivered. Faster construction of U-boats appeared hardly necessary, since, according to the opinion of the political leaders, England was not considered a likely wartime adversary. The objective was believed by the Naval High Command to be operations on the Baltic, especially preparation of defenses against the Russian submarine fleet. Thus at the outbreak of war there were only 57 units completed, of which 46 were ready for immediate operations. To this last group belonged 24 craft of the 250-ton Class, which were unsuited for operation in Atlantic warfare because of their limited radius.
The beginning of the war found the German Navy in the middle of its reconstruction Program. The entrance of England into the conflict on the side of the opposition had not been anticipated and called for a considerable change in the construction plans for new ships. Thus the strengthening of destroyer construction, which had been planned in view of Baltic Sea operations, was delayed in favor of submarine construction. In the Blohm and Voss yards the preparations for construction of the so-called “mobilization destroyer” were already set aside, as the yard made the necessary conversion to produce the submarines needed in the war against Britain.
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Submarine Construction from 1939 to 1943
The German naval high command resolved immediately to conduct an intensive war on shipping. The number of submarines was, of course, small, but it was thought that combined with surface craft and mines, and through teamwork with the Luftwaffe, decisive results could be attained against the enemy’s communications. Profiting by the experience of World War I, an extensive construction program for building up the U-boat fleet was begun immediately. The construction of the vessels on order was well underway by the beginning of the war. They were an advanced type of the VII and IX Classes, which had been tested during peacetime production and had now attained mature form. Thus began the Types VII-C and IX-C, which with minor changes were in production almost through the entire war. The VII-C-boat had a surface displacement of 769 tons, and her twin 1,400 HP Diesels developed a maximum cruising speed of 17 knots. Fuel supply permitted a radius of 7,400 nautical miles at ten knots. Her twin 375 HP electric main engines made possible a submerged speed of 7.6 knots. The two built-in batteries permitted a radius of eighty nautical miles at four knots. The boats had four bow-torpedo tubes and one stern-torpedo tube, and carried nine spare torpedoes. The deck artillery consisted of one 37 mm. cannon and two 20 mm. twin-mount flak guns. The VII-C Class became the most numerous; a total of 659 of these craft was produced. The IX-C-boat, planned for longer transoceanic operations, had a surface displacement of 1,120 tons. At practically the same maximum cruising speed, the vessel had a considerably greater surface operational radius of 13,450 nautical miles at ten knots.
These craft corresponded in kind to the submarines of World War I. They were planned for travel on the surface and were supposed to submerge only in the event of danger or an attack. In accordance with technical progress, the vessel had been further improved: it traveled noiselessly, the batteries were more efficient, the new electrical torpedo showed no wake, and the water-swell on launching the torpedo was eliminated. The magnetic firing of torpedoes, which had been disappointing at first, permitted undershooting the target, thus increasing the explosive effect of the torpedo and causing the cargo vessel to burst open with a single effective hit. Reliable radio transmission equipment made possible the direction of submarines from a central station and led to the development by Admiral Donitz of the “wolf-pack tactics,” which successfully opposed the defense of ship convoys.
At the outbreak of the war, the design of the VII-C-Class was decided under the direction of the Naval Ship Department in the Navy High Command at the Germania-Werft (Krupp) in Kiel. Over-all plans were ready, test units were under construction, and two months later in October, 1939, the Naval Ship Department was given orders to begin the established program at Germania-Werft, the leading yard, and at twelve subsidiary yards. To control the construction of subsequent units, the Nachbaubüro was established at the Germania-Werft. The latter had the task of assuring deliveries of production designs and supporting materials to the subsidiary yards and issued orders for all important deliveries on new construction. Through its knowledge of the work progress at the various yards, it was in a position to stagger deliveries so that there was no slow-up or congestion at any individual yard.
The aforementioned subcontracting yards were both large and small, and with one exception these subsidiary yards were inexperienced in submarine construction, as well as in naval (i.e., warship) construction in general. The difficulties were greater than had been expected, inasmuch as the supervisory personnel from the Navy were not sufficient to instruct the various yards in submarine building, and it was necessary to loan specialized personnel from one yard to another.
The acceptance of materials, machines, and apparatus ordered in the interior operated through the Naval Acceptance Department, which had to check the quality of material and the efficiency of machinery delivered by the individual suppliers.
From the beginning, trouble had been expected from air attacks. The distribution of orders for new construction to many different yards offered some assurance against individual shortages. Likewise, for every part there were at least two manufacturing centers whose individual capacity was adequate for the whole program. Essentially this principle could be applied so that long interruptions in the construction program scarcely occurred.
At the beginning of the war there was a choice of two Diesel motors for the main propulsion of the VII-C. One had a mechanically-geared Root’s blower supercharger, and the other had an exhaust-driven supercharger. While the latter was distinguished by its low fuel consumption, the first named motor had a greater maturity and was therefore chosen as the standard machine for the program.
The manufacture of these motors was carried out in different machine shops. Even in the largest shops, considerable difficulties were encountered at the outset, so that the first deliveries could not be made on schedule.
In order to make economical deliveries, extensive production schedules had been established. During the first series of tests, unexpected difficulties developed, and it took the coordinated efforts of both the large and small plants to iron out the “bugs” in the motors.
In the first year of the war, about two units of the different types were completed per month on the basis of the pre-war contracts still in force. The delivery of the first units was made in October, 1940, at the most efficient yards (cf. Fig. 2) twelve months after the contracts had been let. But not until June, 1941, twenty months after the contracts had been awarded, did the deliveries of the VII-C boats at the thirteen participating yards reach the figure of fifteen units per month according to plan.
The productivity of German shipyards was especially hampered through lack of personnel. As the man hours needed to turn out a vessel varied considerably from one establishment to another, a study was made to investigate the origin of these differences. A group of specialists was organized to set up the basis for a comprehensive uniform work schedule to be applied to the most troublesome phases of the project. In this way, it was possible to compare each step of the work at the various establishments and to determine which method produced the most work in the least time. Regular discussion meetings of the planning groups stimulated more economic production methods. As evaluation of production established an efficiency index of the yards, the workers’ ambitions were inspired to strive for maximum goals. Figure 1 shows the labor expenditure in producing one VII-C unit. The continuous improvement in working economy can clearly be seen. It finally made possible the figure of 220,000 man hours for the completion of one unit, including installation of main and auxiliary engines plus armament. The comparison of production at various establishments enabled us to determine the advantage in greater unit production at a large yard, as well as the initial difficulties at inexperienced yards.
It is obvious that for the consumption per boat, the efficiency of the yard, the contract quantity, and the conditions of breaking in personnel were decisive. The yard with the highest delivery had some 52 units to build per annum. Another yard with an annual output of two units, came in the last place. At a large shipyard, producing one submarine a week, the work groups were so subdivided and specialized that each assembly worker received the same work again after exactly a week’s time. In the case of smaller yards, which delivered only a few boats per year, such an economical labor organization was neither possible nor profitable. Here manufacturing was carried on according to the old handwork methods without exact timing or project planning.
The yards were operating to the limit because of the U-boat construction program, the incumbent repair tasks, and the additional new ship construction. For these reasons, only some 40% of the productive work hours were available to the submarine construction program. In order to relieve the strain on shipyards, the Nachbaubüro strove to consign all work that was not absolutely connected with the shipbuilding program to inland manufacturers. Thus, of the 220,000 work hours totaled under most favorable conditions in the deliveries stated in Figure 1, some 35,000 work hours could still be shifted from the shipyard sector. The great shipyards which were heavily obligated with other construction contracts took advantage of this work delegation to a great extent, while the smaller yards showed a reluctance to assign even the smallest part to other concerns in order to keep their own shops occupied in equal measure. This led to the point where actually at the most efficient yard only about 180,000 work hours per boat were put out by the yard itself, whereas the smaller yards used up to 80% more hours. The great difference in salary costs between large and small yards was compensated for by the fact that the costs for outside deliveries reappear in the greater material costs and that smaller yards made up in savings on managerial salaries for the greater expenditures in work. The difference in the final cost amounted to only about 11%. Less the cost of delivery, which was up to the Navy, the overall cost for one unit including weapons, fire control apparatus, and communications equipment amounted to about 2,000,000 Reichsmarks. Of this sum, 1,350,000 RM went for outside deliveries of propelling machines, auxiliary machines, batteries, and so forth, as well as for shipbuilding, machine work, and electrical material.
Figure 2 shows the number of U-boats built per month during the War, the total number, the number of VII-C-boats, and that of Type 21. From this we can see the beginning of deliveries after the war construction program was set in the middle of 1940; the high point reached in 1941, with fifteen vessels per month; and the uniform conduct of the program. The effect of the war, air attacks, and so forth, on construction was relatively slight up to the middle of 1943. The drop in the curve during the winter of 1941–42 was caused by heavy seasonal frosts which had a damaging effect on work in the building slip. In Figure 2, the number of vessels is given for the months before these units were taken over by the Navy. This acceptance included a brief test of the engines and apparatus, a short diving test at the yard, and a one-day acceptance trial on the surface with a crew assigned by the yard. After this examination trip, the Navy took over the vessel. For the shake-down cruise, the final trials and acceptance by the Navy Testing Command, an average of ten-and-a-half weeks was needed, after which the vessel would return to the yard for elimination of any defects that had turned up in the tests. The craft was then fitted out within about a week and assigned to front line duty. On the average, it took from three-and-a-half to four months for the submarine to reach its assigned hunting ground after delivery.
The Development of the Submarine War from 1939–1943
The delays at the start of the construction program, plus the long time required for training and testing, had an unfavorable effect. After a year-and-a-half of war, a total of one hundred submarines had been built, but only twenty-one of these were actually available for the Front. Usually a third of the vessels was undergoing repairs in the yards, and another third was proceeding to or from the hunting grounds, so that relatively few U-boats were in the operational zones at any one time.
However, the clear decision at the war’s outset to wage an intensive submarine war against commerce brought noteworthy success in the first stage, despite the limited number of boats ready for action. In World War I, the monthly tonnage sunk reached its peak only in the third year of the war when unrestricted submarine warfare was declared in 1917. The highest success per boat on the average was reached during this phase. By strengthening their anti-submarine warfare, the Allies were able to cut this success in half during the course of the following year, although the number of U-boats remained the same.
It was quite different in World War II. The initially undeveloped anti-submarine warfare of the enemy, the greater effectiveness of the new submarines and their weapons, the comparatively heavy commercial traffic, and the added advantage of operating between the coasts of Norway and France enabled the submarines to reach an average total of sinkings which far exceeded the totals of World War I. Thus, despite the small number of operational submarines, a high overall score was made. In 1942 this increased with the growing number of submarines, though the success per boat dropped considerably because of the growing effectiveness of anti-submarine warfare. These ratios are clearly to be seen in Figures 3 and 4, which set forth the totals of monthly tonnage sunk and these totals in relation to the number of existing U-boats.
The impending air superiority of the enemy, with the increased patrol actions, gave the U-boats a great deal of trouble, despite the latter’s anti-aircraft weapons, which had been strengthened in the meantime. These patrols stretched farther and farther out from the coastal areas into the Atlantic. After the aircraft carrier came into the game, in patrolled areas the submarines could scarcely show themselves during the day, so that only at night could they take advantage of their superior surface speed and charge their batteries. By the end of 1942, U-boat losses had increased alarmingly. Vessels with both experienced and inexperienced crews failed to return from the hunting grounds for causes unknown. The alarmed U-boat Command held the submarines at their bases as the first hint of new enemy counter-measures came from reports of vessels which had been subjected to bombing attacks by planes on nights of zero visibility. The enemy had developed radio locating-devices similar to those already used by the Germans, but for short-waves, and had equipped his planes with such gear. The subs were thus driven under water even at night in patrolled grounds, and their effectiveness greatly reduced. The war on shipping, which had been brought to its greatest success in the year 1942, now suddenly threatened to end in fiasco. At any rate, the use of submarines in strictly patrolled areas became unfeasible and was confined to waters where anti-submarine measures were less well developed. With the rising losses in submarines, sinkings became fewer and fewer.
Through the construction of new yards in the United States and the application of more systematic and efficient production methods for the construction of simpler ships, the Allies had in the meantime increased their ship construction to a high degree (Figure 3). By the turn of the year 1942–43, the monthly increase of commercial tonnage had overtaken the monthly total of tonnage sunk, and during 1943 surpassed it to such an extent that it became extremely doubtful whether a revival of the submarine war with new means could have a significant influence on the further course of military events.
Although it is difficult to understand in retrospect, it was believed on the basis of existing estimates of new developments in propulsion and improvement of weapons that victory was possible in the battle of the Atlantic, and the German economy was geared to a great extent toward the construction of a new type of submarine.
The appearance of aircraft with excellent radar equipment, together with the use of acoustic devices on ships which took bearings on the submarine’s activity by radiating high frequency sounds, had made the submarine an obsolete weapon. The first-named location method had driven the submarine under water in patrolled areas, so that much of its mobility was lost; the last-mentioned device made the submerged craft recognizable to the pursuing craft. Against suitably equipped enemies, the submarine had lost its strongest weapon, namely its invisibility. Since the effective distance of underwater sound devices was quite limited, the radar locators were at first the most dangerous. Despite the fact that immediately after this was recognized devices were installed on the submarines which indicated a ship’s position on the radar scope as soon as the bearing of the ship was determined and that protection which lessened the bearing ray’s reflection was developed for the superstructure of the submarine, the chief problem was to have the submarine disappear as far as possible under the surface of the water. Up to this point the submarines had been forced to surface regularly in order to charge their batteries, or, with the help of their greater surface speed, to cover greater distances. The new problem, therefore, required new solutions.
Developments which had been made in this direction at the beginning of the war were not continued or expanded in the first years of the war. The submarine command took the point of view, on the basis of the initial successes, that existing German submarines were the best in the world, and in the belief that they were bringing the war to an end, had, before the basic developments could be brought to maturity, recommended only such isolated developments as promised to pay off immediately. The application of a series of developments was indeed made in the early summer of 1943, but this decision, despite all the preliminary work, came too late.
The snorkel had been known at the beginning of the war, when it had been produced on a limited scale and little importance had been attached to it. Its significance was appreciated only in the urgent circumstances of 1943, and the development of the snorkel submarine was not possible before the summer of 1944. The units equipped with snorkel acquitted themselves admirably and were able to penetrate into the most heavily patrolled areas and there operate successfully, cruising submerged for weeks at a time.
In order to produce a submarine with wider submerged radius as well as greater underwater speed, preliminary designs for higher speed and efficient new type engines to operate independently of air-oxygen had been developed. These developments, however, for the above-mentioned reasons, had not been pushed, although an experimental model had been produced as early as 1941. Only in 1943 were they seriously taken up again. It was a question of engines which used oxygen either in pure or in chemically bound form as the generating power for combustion—in other words, the Walter engine and the Kreislauf (closed circuit) engine.
The Walter drive used an 80% hydrogen-peroxide solution for generating power. When this substance is accompanied by a suitable catalyzer, it is split into water vapor and oxygen, with a consequent release of heat which can be used in the propelling turbine. The above-mentioned experimental craft produced in 1941 had a driving motor on this “cold” method. Through the additional combustion of fuel oil in the oxygen-gas mixture (hot method), the output could be raised considerably. Seven units (Type 17) with this propulsion were produced by the end of the war; they did not, however, complete their trials. With them underwater speeds of 24 knots were attained for the first time.
The Kreislauf (closed-circuit) engine did not allow such a concentrated output as the Walter drive, but it was not dependent on scarce hydrogen-peroxide and promised to give a great submerged operational radius. For both submerged and surface travel it used one Diesel engine. This engine operated in the usual fashion on the surface, but in submerged movements only a part of the exhaust was released, while the rest, cooled and purified, was reintroduced via the air intake along with pure oxygen. In order to attain a sufficient radius, the oxygen had to be carried under hitherto unfeasible high pressure (400 atmospheres) or in fluid form. Engine installations of this type had by the war’s end been tried in mock-ups on land, but had not been used in actual submarines. Part of these installations were developed at reduced output for use in the smallest two-man submarines.
In the search for new means to extend the U-boat warfare, it became clear by the spring of 1943 that no operational weapon was to be expected from this resumed development of new type propulsion in the immediate future. However, the military situation demanded the most rapid reorganization and interest turned at first to the further development of known installations with electric propulsion for submerged operation. The latter had the advantage over the above-mentioned types because through charging the batteries the radius of submerged travel could be restored at any time. By increasing the electrical capacity of the batteries and the effectiveness of the driving motors, as well as creating a submarine design particularly suited to rapid underwater movement, it was possible to meet the demand for increased submerged radius and speed. The working out of this project led to Types 21 and 23, whose essential characteristics are presented in the table at the bottom of the next page.
The indicated values show that power plants had been developed which made possible a new type of attack. Using the snorkel, these submarines were able to operate entirely underwater. Both in attack and in the subsequent escape maneuvers they made underwater speeds twice as great as those formerly attained.
Construction of Submarines from Type 21
In the summer of 1943, the military establishment demanded that the new submarines be ready for operations by the end of 1944, that is, the first units should be coming out in April-May, 1944. The full production Program called for 33 units per month and
Output of Diesels
Output of electric motors
Max. surface speed
Max. underwater speed
15,500 naut. miles at 10 knots
2,800 naut. miles at 8 knots
285 naut. miles at 6 knots
175 naut. miles at 4 knots
was to be reached by September, 1944. This demand meant an increase in U-boat production of more than 60%. A major difficulty was the fact that no increase in the number of shipyard workers could be expected; on the contrary, there was a prospect that all able shipyard workers would be inducted into the fighting forces. As a substitute it was proposed to assign foreign workers, prisoners-of-war, and women. If the new construction program was to be carried out, all available means of production would have to be drained to the end. This could only be effected by an authoritative organization which could keep both the shipyards and.delivery industry under strictest control. Under the direction of the armaments ministry, standing committees for the essential branches of industry were made responsible for the execution of the preparations plan. With the mobilization of additional good designers, industrial engineers, planning and estimating experts, industrialists, and first-class naval experts, the planning program was brought to a stage of perfection. Under the code name of Ingenieurbüro Glückauf, this central commission began its work in the little city of Blankenburg in the Harz Mountains, where there was less likelihood of disturbance from air attack than in the great ship construction centers.
The thought of attaining a maximum output with a minimum of labor man-hours led to the planning of prefabricated sections at all yards. This entailed a division of the general task among the participating yards on a parallel, mass-production basis. The tasks had to be carefully controlled by means of an exact work plan involving stringent coordination of the respective time tables.
The submarine was divided into eight sections which were produced separately and then assembled. The construction of the pressure hull of the single section, the installation of water-tight bulkheads and the bottom plate—in other words, the iron work—was allotted to steel works inland. From these establishments the sections were transported by inland waterways to the so-called section yards. The latter had to effect complete installations of main and auxiliary engines, communication systems, conduits, and electric wiring in the delivered sections. The assembly of the prepared sections on building slips and docks was effected in assembly yards to which the sections were transported by sea. Power trials and delivery of the completed boat were carried out at the assembly yard.
The highest circles in the conduct of our air warfare believed that by spring, 1944, a “protective roof” could again be placed over the Reich proper, but even though the promise of a “protective roof” was not fulfilled and the enemy air attacks grew stronger from month to month, they could not paralyze submarine construction.
Taking into account possible disruptions by enemy air attack as well as the traffic situation, three assembly yards were set up for Type 21. Of the 33 boats to be delivered per month, eight were assigned for assembly to Schichau yard, Danzig, thirteen to Blohm and Voss, Hamburg, and twelve to A. G. Weser, Bremen.
The sections prepared for assembly were accordingly to be delivered by yards lying in the periphery of the assembly yards, so that three large production areas could be drawn, namely the Hamburg-Kiel area, the Weser district, and the eastern district around Danzig, which had the disadvantage of distance from steel-producing regions but enjoyed a certain immunity from air attack almost up to the end of the war. In this way, each type of section was being produced in three different areas, with the exception of the after-section whose construction for the two western assembly yards was concentrated at Kiel. It may be considered a miracle that no disturbance from air attack was felt at this sensitive point. The geographical location of assembly and section yards may be seen in Figure 5, to which are added the Naval Department for Ship Construction in Berlin and the Ingenieurbüro Glückauf, which had been transferred to Blankenburg.
In view of the deteriorated military situation, the timetable for production of the Type 21 boats was figured very closely. It has been stated above that this production was decided in July, 1943, and that outside of a preliminary draft no production drawings were ready. Due to lack of time, it had to be planned for the entire series, besides three experimental models which were put out in a hurry. As a test of the new construction procedure, these units were designed also for prefabrication. The first sectional parts for these were to be produced by the steel construction works by January, 1944; the sectional and assembly yards were given a deadline of four months, or until the end of April, 1944, for the delivery of these first three boats to the Navy. This meant an overall construction time of nine months for these boats which were twice as large as the VII-C Type. Moreover, the entire design had to be worked out, the assembly plans Prepared, and a new type of production Perfected. If the program came due in September, 1944, with at least 33 boats per month, a production time of a bare six months was foreseen. Of this time, sixteen days were needed for the smoothing of the metal plates and transport to steel construction works. Here it took about forty days for steel work on sections, then about fifty days in section yards for the completion of sections, and in the assembly yards some sixty days for assembling and testing of the completed craft. An additional nine days were provided for transportation.
The original construction program and the number of boats actually delivered per month are indicated on Figure 6. Here is the great discrepancy between the first estimated timetable and the results attained. It must, of course, be assumed that such a new kind of production would present many unforeseen technical and organizational difficulties. But it must be stated that the delivery date for the submarines stemmed from an over-estimation of the current possibilities on the part of the leading figures of the Chief Planning Committee who were not from the shipbuilding industry and did not appreciate the many difficulties already besetting the shipyards. They had accordingly made promises greater than they could fulfill. On the other hand, the rigorous demands of this program inspired all parties to greater effort. In all critical evaluations of the submarine building program, the Chief Planning Committee must be condemned, because it set standards for delivery which could not possibly be carried out and could only cause trouble all along the line. Needless to say, there was an important difference between 233 units of Type 21 theoretically ready on schedule and only eighty such craft actually in operation by April, 1945.
Apart from these considerations, however, the construction of this submarine class gives a good indication of the effectiveness of German industry. The simultaneous construction of the prefabricated sections in plants throughout the Reich, with closely coordinated assembly at only three geographical points, presupposes such an integrated organization and such an efficient system that considering the constant air attacks and the great destruction caused by them, it is astonishing to see how effective German industry was after four years of war and how new ways were always found to meet the demands of the construction program.
On August 1, 1944, or twelve months after the awarding of contracts and after the beginning of unit construction, eight boats of Type 21 had been delivered to the Navy, and the production at the yards was in full swing. The increase in effectiveness is indicated in Figure 7, which shows a decided jump in the quarterly production of U-boat tonnage in the final phase of the War.
For the over-all work on Type 21, including steel construction and delivery in the shipyard, 260,000 hours per boat were calculated. In fact, the first boat for which a total reckoning was made required 30% more hours. According to experiences with the VII-C-boats, it can still be correctly assumed that both the over-all construction time of 25 weeks and the calculated work expenditure were attainable. If one compares the work expenditure for steel construction at a large yard and the work performed at the yard for a VII-C-boat with the corresponding work expenditure actually necessary for a Type 21, we get a ratio of 180,000 work hours to 330,000 work hours. Bearing in mind that the weight of the boat less weapons, fuel, and equipment was about twice as great for the Type 21 as for the Type VII-C, the prefabricated construction presents an important step forward economically. If we take the calculated cost of Type 21 as a basis, we get a delivered cost for the craft without load of 3,600 Reichsmarks per ton as compared to 3,300 RM per ton for the VII-C. The difference is quite moderate, in view of the much more powerful propelling installation of Type 21.
The increase in production was reached with a shipyard personnel that remained throughout the war’s duration at some 145,000 men. It must be noted, however, that the quality of personnel was constantly weakened by the withdrawal of workers fit for military service, with no replacement of workers of equal experience.
As has already been mentioned, the transition to the new U-boat construction in the summer of 1943 occurred so suddenly that it was not possible to produce experimental test models before the craft went into production. It is obvious that with a type entailing all sorts of new elements, the training of the crews and the testing of the first submarines required a longer time. In addition, there were a number of improvements which had to be added before a submarine could be considered fit for front-line operations. Because of the accelerated program, these improvements could only be added subsequently. Thus, up to the end of the war, no single unit went into action as a finished product.
When one considers the U-boat policy in retrospect, it becomes evident that the great concentration of material and manpower for the construction of the new types was useless. It is true that had the war lasted into the summer of 1945, a larger number of highly effective new U-boats would have reached the front. A decisive success could not have been attained by the submarine weapon even with the new improvements, in the face of Allied air superiority together with the greatly increased commercial tonnage and the increased effectiveness of American cargo ship production.
By the summer of 1943 the U-boat had ceased to be a decisive factor in the war, and could not again become one. It is a question whether the outcome of the U-boat war had not already become apparent to German political leaders. As a result of the neglect of technical developments up to this time, the change-over to production of new types entailed a great loss of time. If we had confined ourselves to equipping existing submarines with snorkels and replacing them with new construction as they were lost, we would have been quite as successful and would have obliged the enemy to maintain his vast and costly anti-submarine organization.
The powerful German war potential which was devoted to U-boat construction could have been applied to other important military goals, such as strengthening the antiaircraft defense, building tanks, or erecting fuel production plants, the lack of which finally brought about the collapse of the German defense.
In a comparison of the three great U-boat construction periods discussed here, it can be seen that on the basis of accumulated experience U-boat construction was brought to ever-increasing effectiveness. The groping and unorganized program of World War I was followed in World War II by a well-defined standardized construction program which was maintained with great regularity until the next to the last year of the war. The decision in the summer of 1943 to attempt, despite the strong enemy defense, to turn the tide of war to the German advantage in the Battle of the Atlantic by the introduction of a new type of submarine led to the attainment by new production methods and organization of U-boats which, despite the increased difficulties of the war, exceeded the output of the shipbuilding industry up to this time. If this last attempt was in vain, the output and efforts of the submarine construction workers are worthy of a place in history beside the U-boat crews, who stood faithfully at their posts to the end.
A graduate in marine engineering from the Berlin Technical Hochschule twenty-five years ago, Mr. Kurzak has been a professional marine engineer and constructor ever since. From 1937 to 1940 he was charged with control of shipbuilding at the Deutsche Werke and Germania-Werft in Kiel, where the larger part of the World War II German Navy was built. In 1944 he was recalled to active duty in the German Navy for independent development of the Kreislauf (closed cycle) submarine engine. Since 1949 he has been attached to the German Patent Office, Munich, in connection with shipbuilding and marine engineering items.
THEY’RE A COOL LOT
Contributed by COMMANDER W. J. RUHE, U. S. Navy
The sang-froid of British destroyer skippers during World War II was a continuous source of wonderment to our own tin-can officers. The Kearny's skipper had been so impressed when he’d run across a lone British destroyer in the Mediterranean and, on closing, been shocked by the casual greeting which came over the TBS. “I have a Fritz beneath me. Would you care to join me?”
Several nights later, en route to Naples, a radar contact had been reported at 12,000 yards. The contact was closed to 9,000 yards, tracking at 11 knots. “It must be a Nazi sub,” the skipper concluded as he peered into the blackness ahead. On the chance that it might not be, he repeatedly tried to raise the unknown ship on the TBS. Only silence greeted his attempts at recognition.
With the range continuously closing, he ordered “open fire.” A salvo of four guns shattered the stillness. Then deadly silence. Seconds later the TBS on the bridge broke into an annoyed chatter.
“If you’re shooting at me—they’re all overs,” issued forth in a clipped British accent.
(The Proceedings will pay $5.00 for each anecdote submitted to, and printed in, the Proceedings.)