An essay submitted in partial fulfillment of the requirements for the degree of Master of Arts in Military History Norwich University.
VADM Sagerlwlm is a retired submarine officer. He commanded USS KAMEHAMEHA (SSBN642) and was Deputy Director of Naval Jntel/ige11ce. As a Flag Officer he served as Commander, South Atlantic Force and as Com-mander, Naval Education and Training.
On 3 September 1939, Britain and France declared war on Germany in response to the German army’s invasion of Poland. Late that same day, U-30 was on patrol at periscope depth south of Rockall, 120 miles west of Scotland. As night approached, the U-boat’s captain, Kapitiinle11tna11t Fritz-Julius Lemp, was tracking a large ship that was blacked-out and was steering a zig-zag course at high speed, leading him to conclude that it was an armed merchant cruiser. Lemp fired two torpedoes, one of which hit, causing the vessel to stop and slowly begin to sink. He had torpedoed the 13,600 ton British liner A TH EN IA carrying over 1100 passengers, of whom all were rescued save the 118 killed when the torpedo struck.’ What came to be known as the Battle of the Atlantic had begun.
n view of the Imperial German Navy’s extensive U-boat campaign in World War I, the German Navy in 1939 arguably possessed the most experienced submariners of any navy in the world. Their exploits in 1916-1917 had nearly brought Britain to its knees, yet their campaign ultimately had failed. The same fate awaited the U-boat force of World War 11, despite the expertise gained in the previous war. This paper seeks to determine why the U-boats lost the Battle of the Atlantic.
Inspired by The influence of Sea Power Upon History, Alfred Thayer Mahan ‘s description of sea power’s role in making Britain a world power, and strongly encouraged by his state secretary of the Imperial Naval Office, Admiral Alfred von Tirpitz, Kaiser Wilhelm II in 1898 had embarked on a naval building program designed to make Germany a leading naval power, second only to Britain. By 1914, the Kaiser had reached his objective, but the reaction of Britain to the High Sea Fleet now sitting in its Baltic and North Sea bases was to build even more ships and, much to the Kaiser’s dismay, to join with former foes, France and Russia, in forming the Triple Entente. Wilhelm had naively expected his cousin, George V, to welcome the Imperial German Navy as a potential ally against France, but instead he saw Germany encircled by the Triple Entente. Britain had historically viewed any strong European navy as a rival of which to be disposed, and the German High Sea Fleet was no exception, a history lesson that Wilhelm had somehow failed to learn.
When war erupted in 1914, Germany’s High Sea Fleet was immediately blocked from access to the Atlantic by the forces of the British Grand Fleet, a situation that led in 1916 to the battle of Jutland, in which the High Sea Fleet managed a tactical victory, but was unable to break the strategic blockade imposed by the Royal Navy. This led to the decision to engage in unrestricted submarine warfare in an attempt to bring Britain to the negotiating table by cutting its import of needed war materials, especially oil, and foodstuffs, a gamble that was succeeding until Britain instituted the convoy system at the urging of Rear Admiral William Sims of the U.S. Navy. The gamble had brought America into the war, and indirectly thereby brought on the convoys that turned the tide against the U-boats.3 The experience gained by both sides in the First World War would be influential in determining the course pursued by each in the Second World War.
The Treaty of Versailles that officially ended World War l in 1919, among other restrictions on the German armed forces, prohibited any submarines in the German navy. Nevertheless, Germany took steps to maintain the submarine design expertise developed during the war. Taking advantage of requests from other navies for advice and assistance in submarine construction, Germany established a design bureau in the Netherlands that ostensibly belonged to a private German company but in reality was a part of the German naval command. By performing actual work for its foreign clients, the bureau was able to develop submarine designs intended for eventual use by the German Navy.
However, designing a submarine is only the beginning of the building process, and Germany was prevented by the terms of Versailles from building submarines in German shipyards not only for itself but for export as well. Although Germany let secret contracts in Spain and Finland for submarines built to designs developed jointly with the contracting countries, the work force was necessarily that of the foreign yards.5 Thus, the unique critical skills needed for U-boat construction in Germany naturally withered with the passage of the years. While a sufficient number of skilled workers were still available in 1935 for limited production of new submarines, an acceleration and/or expansion of construction ran the risk of deterioration in the quality of the work. In addition, the designers tended to follow World War I designs, resulting in boats with only limited improvements as compared with the United States Navy’s fleet boats, particularly in habitability, sea-keeping and long endurance, and the capacity for addition of new equipment such as radar.
Following the accession of Adolph Hitler and his National Socialist Workers Party to power in 1933, the Nazi government, in a series of bold actions, executed a de facto repudiation of the Versailles treaty. In 1935, an increasingly resurgent Germany confronted a still war-weary Britain with demands for an expanded navy, and in June, the Anglo-German Naval Agreement was signed by which the German Navy was permitted to rebuild, but was held to a limit of 35 percent of the tonnage of the Royal Navy except for U-boats, which had a limit of 45 percent of the British submarine tonnage. Under certain circumstances, the U-boat tonnage could equal that of the Royal Navy. The 45 percent limit amounted to 24,000 tons, so although the percentage was higher than the rest of the navy, the actual tonnage was the smallest allowed for any arm of the navy.
Given Britain’s experience with German submarines in World War I, the agreement to allow a rebuilding of the U-boat arm begs the question as to why. Part of the answer may be that the senior leadership of the Royal Navy was not inclined to sec submarines as more than supplementary craft to be used for reconnaissance and picket duties, and considered that future numbers of British submarines would be sufficiently low so as to make the number allowed to Germany minimal. In addition, the British were assured by the developers of ASDIC, the active sonar carried on surface ships, that its detection capability would defeat any U-boat threat. Such reasoning was in accord with the British government’s wish to avoid confrontation with Germany, and the result was Britain’s agreement lo Hitler’s demand to rebuild the U-boat force.
In view of the restriction on total tonnage, the U-boat arm was faced with the choice of building either a relatively small number of larger, long endurance, ocean-going submarines or a larger number of smaller U-boats of less endurance, smaller torpedo load, and moderate range. Compounding the problem of restoring the U-boat force was the London Naval Agreement of 1936 that imposed on submarines the requirement to abide by prize rules when attacking merchant shipping.9 This had the effect of inhibiting support for a U-boat program that necessarily competed with surface ship construction for funds and materials.
Captain Karl Donitz, a veteran U-boat captain of World War I, was selected in 1935 to command the U-boat flotilla. He had witnessed the effectiveness of the convoy system in World War I, and credited it with defeating the U-boat campaign which had been conducted by boats acting independently in single boat attacks.10 After periods of irresolution by the Kaiser and his chancellor regarding whether to permit unrestricted submarine warfare, the straits in which Germany found itself in the winter of 1916-1917 pressured the Kaiser into approving an all-out U-boat effort, starting in February. The tonnage sunk per month increased dramatically, and by the month of April reached 860,000 tons, an amount that, if sustained for four more months, would have forced Britain to sue for peace. Instead, the convoy system was instituted in May 1917 and the losses quickly declined, with a concurrent increase in the loss of U-boats.
As a result of his experience in World War I, Donitz was convinced that the answer to the convoy system was the concentration of U-boats in coordinated massed attacks on a convoy. The intent was to overwhelm the escort defense, and the confusion thus caused among the escorts would create opportunities for attacking the merchant ships with a reduced probability of successful escort attacks on the U-boats. Accordingly, he pressed for numbers as opposed to size, whereas the Naval High Command (OKM), viewing group tactics as requiring an excessive breaking of radio silence, opted for a mix of medium and larger U-boats that would operate in the single boat tradition of World War I. The final decision rested with the Commander-in-Chief, Grand Admiral Erich Raeder.
Chancellor Hitler had repeatedly assured Raeder that Britain would not go to war over land considerations in Europe, an assertion apparently confirmed by the repeated British acquiescence to Hitler’s moves in re-occupying the Rhineland, in rebuilding the armed forces, and in occupying Czechoslovakia and Austria. In 1935, with the signing of the Anglo-German Naval Agreement, Hitler had informed Raeder that the build-up of the Gennan navy could start, and Raeder accordingly ordered the commencement of his plan for a balanced navy, with completion of the plan scheduled for 1948, a date later moved up to 1944, requiring an acceleration in the building rate.13 It was Hitler’s policy in 1935 lo avoid war with Britain, and Raeder’s plan initially at least claimed lo adhere to the restrictions of the 1935 Naval Agreement, including the limit of 24,000 tons for submarine construction. The first thirty-six U-boats ordered by the OKM totaled 12,500 tons, and included prototypes secretly built and tested before 1935 in Finland and Spain. With that head start, the building yards completed thirty-five of the thirty-six in the next eighteen months, delivering twenty-four Type II (250 tons), two large Type I (750 tons), and nine Type VII (500 tons) by the end of 1936. The tenth Type VII was completed in 1937.
he dispute between Donitz and OKM centered on the remain-ing 11,500 tons allowed for U-boat construction. Donitz wanted to use the entire amount to build twenty-three Type VII medium-range boats, while OKM pushed for twenty-three mixed types, consisting of eight small Type lls, eight large, long-range improved Type Is, and seven improved Type Vlls. After months of delay, Raeder approved the OKM plan. The delay and the subsequent decision to build the larger Type Is set back the overall delivery of U-boats, with only the one Type VII completed in 193 7. I 93 8 saw nine boats reach the fleet, while twelve were received by I September 1939.
Donitz advocated a strategy of attacking Britain’s shipping with the goal of simply sinking more ships than could be replaced by Britain’s shipyards, thus eventually so weakening the British war effort that Britain would have to sue for peace. He had determined that the U-boat force should have at least 300 boats in order to commence an effective campaign employing wolf-pack tactics against British convoys. However, when war was declared by Britain and France on 3 September 1939, he found his force to be only fifty-seven U-boats, thirty of which were the small coastal boats used for training in the Baltic, leaving a force of twenty-seven larger submarines, of which twenty-two were ready for duty in the Atlantic. Seven more boats were delivered to the navy by the end of 1939, but to Donitz, the German Navy in 1939 “was like a torso without arms.
Donitz was not easily discouraged in his dispute with OKM, and continued his efforts to convince Hitler and Raeder of the need to make submarine construction the navy’s top priority. The Type IX had replaced the Type I as the long-range boat, and Donitz wanted to concentrate construction on Type Vlls and Type IXs in the ratio of three Vlls to one IX. At a meeting in late August 1939, Donitz and the German fleet commander Admiral Hermann Boehm persuaded Raeder that the impending invasion of Poland would bring on war with Britain and France, Hitler’s assurances notwithstanding, and urged him to scrap plans for large surface ships and instead build with all speed possible 300 U-boats, to include 200 improved Type Vlls. Raeder agreed, and several days later, OKM scrapped the long-range balanced fleet plan and instituted Donitz’s plan.17 Germany built I, 152 U-boats by war’s end, of which 704 were the several variations of the Type Vil, while 236 were variations of the Type IX long-range boat.18 These two types were thus the principal German players in the Battle of the Atlantic, and the success or failure of the Atlantic U -boat campaign rested in large measure on their capabilities.
The original Type VII boat, U27, was based on the UBIII class of World War I, modified by means of the experience gained in the work done for foreign navies in the inter-war period, and was laid down in November of 1935. The Type VII variations evolved from the 500 ton short-range boat of 1935 vintage through successive stages of improvements that increased the operating range by addition of saddle tanks for extra fuel, and shortened diving time from 50 seconds to 30 seconds. Later in the war, the 88mm deck gun was removed, and anti-aircraft guns were added on an enlarged deck aft of the bridge. With several exceptions, Type VII variations had four bow torpedo tubes and one stern tube. They were manned by four officers and fifty-six enlisted who lived in a steel tube ten feet in diameter and 148 feet long from the forward torpedo tubes to the stem torpedo tube, crowded with machinery and other equipment. The designer did little to improve the habitability over that of the UBllI boats. There was barely enough water produced by the evaporator to provide for cooking and drinking, certainly none for showers or laundry. The ventilation when submerged was simply a matter of moving stale and odorous air from one compartment to another. Carbon monoxide accumulated in the atmosphere while submerged, and could reach dangerous levels if a boat was forced to remain under water for a period longer than 24 hours while under attack. Machinery was cooled by sea water, and any leakage onto the batteries as a result of being depth-charged caused the release of deadly chlorine fumes, forcing the boat to surface. Of the two heads on a boat, only one normally was operating, the other being used as a storage locker for canned foods; as a result, there usually was a line of men waiting for its use. If the flushing valves were operated improperly, the pressure expelled the flushing sea water into the boat instead of out, with resultant ill effect. In short, the habitability of the Type VII variations was far below that of U. S. submarines. Such living conditions over time have an adverse effect on performance that is insidious in that one is not aware of it, just as an alcohol-impaired driver is unaware of his erratic performance.
The Type VII variations displaced roughly 770 tons surfaced, 870 tons submerged, and were capable of 17 knots flank speed on the surface and a maximum speed of 8 knots for one hour while submerged. The Type VllC and Type VJIC/41, which together comprised 660 of the class, had a surface range of 8500 nautical miles (nm) at I 0 knots, while the VllD with an additional 50 tons of fuel had a range of 11,200 nm at I 0 knots; designed for dual minelaying and torpedo attack, only six VIIDs were built.
In the last two years of the war, the U-boats were forced to travel submerged due to Allied aircraft coverage of the North Atlantic, surfacing only as needed to recharge the batteries, and at the slow submerged speed required for sustained underwater transit, usually 2-3 knots, by the time that a boat reached its station, it could only remain for a few days before beginning the slow transit home. Installation of the Dutch-invented snorkel obviated the need to surface for charging the batteries, but could cause massive flooding if not secured properly when not snorkeling. The head valve in the air intake mast was designed lo shut whenever sea water washed over the top of the mast but when it did so, the air inside the boat was sucked up by the diesels that continued to operate, causing a partial vacuum in the boat. When the top of the mast was clear of water, the head valve opened, causing a rapid increase in air pressure. The rapid fluctuations in air pressure in the boat was a source of considerable discomfort and even pain for the crew, and snorkeling was not always welcomed by the sailors, especially in the rough waters of the North Atlantic.
The Type IX variants were designed to provide boats capable of transits to and from distant locations, with “good endurance and a substantial load of weapons, fuel, and supplies.” The most numerous of the variants were the Type IXC/40, of which 95 were commissioned. With a length of 252 feet and a beam of 22 feet, the IXC/40 displaced l, 120 tons surfaced and 1,232 tons submerged. Cruising speed was 12 knots with a range of 11,000 nm on 214 tons of fuel. Top speed surfaced was 18 knots, while the submerged one-hour rate was 7 .3 knots. Armament consisted of four bow torpedo tubes and two stern tubes, 22 torpedoes, a 105mm deck gun, and a 37mm and a 20mm AA battery. Unlike the single hull Type VII, the Type IX was fully double-hulled, giving added resistance to damage from depth charges. However, its diving time at 55 seconds was almost double that of the Type VII, a factor that could be critical when under air attack.:: Habitability was better than the Type VII, being more spacious and having crew quarters that did not require sleeping among torpedoes, but the standards were still well below those of the U.S. submarine service.
A comparison of the Type VII with the Type IX raises the question as to why Donitz preferred the less capable Type VII. Donitz saw in the Type VII a submarine that could be produced more rapidly than a larger boat while still retaining sufficient weapons capacity to be effective in wolf pack operations, the latter being the tactic that he was convinced was the means by which the German navy could defeat the convoy system. According to Donitz, the Type VII was harder to detect than a larger boat, was easier to handle while submerged, and with the addition of saddle tanks, its range was adequately increased for North Atlantic operations. He was intensely determined to get U-boats to sea in the numbers he had calculated as being necessary to wage a successful campaign against Britain’s vital sea lines of communication, a number he estimated to be 300 U-boats, on the basis of I 00 on patrol, I 00 in transit, and 100 in port for refit and repairs, and recreation and rest for the crews. He considered the Type VII the best compromise between the need for numbers quickly delivered and the level of capability required for effective coordinated attacks on convoys. “For its size, it had the greatest possible fighting power. Its diving time was 20 [sic] seconds; it behaved very well under water; and it was relatively fast-16 knots-and handy on the surface.
At the same time, Donitz recognized that there likely would be a need for a larger, long-range boat roughly half again the size of the Type VII. Thus was born the Type IX, a boat that, in the eyes of Donitz, was slow in diving, not as easy to handle submerged, and was easier to detect because of its size. Its best features were its endurance and range of operations. Donitz’s solution was to recommend a mixed force of three Type VIIs to one Type IX, a ratio that was roughly maintained throughout the war, and a decision that was one of several critical decisions affecting the outcome of the Battle of the Atlantic.
At Donitz’s urging, the submarine construction program received orders to be accelerated and expanded in October 1939, but it was not until a year later that the orders took effect, due to the higher priority in allocation of materials to the army and the Luftwaffe. In 1935, the OKM had warned that German shipyards were neither capable of accelerating construction nor of expanding, due to a shortage of workers. By 1940, the situation had been changed by the use of imported labor from occupied territories, but quality suffered due to insufficient numbers of skilled workers resulting from no submarines having been built in Germany for the past twenty years. While the OKM had been referring to surface ship construction, the same risks applied even more to submarines. As evidence of inferior design and construction, in addition to the poor habitability previously mentioned, there were far more serious errors revealed when the boats were subjected to the stresses of depth charges. For example, the two diesel engine exhaust valves in the Type VII boats had been installed with the valves closing against sea pressure instead of with sea pressure. As a result, when the boats were under depth charge attack, the force of the explosions, which increased with the increased pressure of the water as depth increased, hit the scat of each valve like a giant hammer, causing the valves to unseat, allowing sea water to flood the engine compartment. The after battery room was immediately forward of the engine room and when sea water entered it, the reaction with the battery acid caused the emission of toxic chlorine fumes. It was not until a damaged U-boat managed to return to Germany and reported the casualty that it was recognized as a hazard and was corrected.
The principal weapon of the submarine is the torpedo. The German torpedo experts had anticipated the eventual restoration of the U-boat force, and had spent the period between the end of World War I and 1935 in developing a magnetically activated firing mechanism that detonated when a torpedo passed through the magnetic field of a steel vessel. The running depth of the torpedo was set to allow the torpedo to pass under the target vessel where the torpedo’s explosion broke the keel of the ship, sinking it with one shot. The torpedo technicians had also designed a new contact detonator that was described as being more reliable than the detonators used in World War I. However, early in the war, it became apparent that the magnetic pistol as the Germans called it was not operating as intended. “V cry frequently the pistol detonated too early while the torpedo was on the way to the target; or it detonated at the end of its run; or it failed to detonate at all, even when passing beneath its target.” Reports also were received of contact detonators failing to detonate when hitting a target.2s The ensuing investigation additionally determined that torpedoes tended to run deeper than the set depth. The most egregious example of torpedo failures occurred during the attempt of the U-boats to intercept the British landings at Narvik, Norway in March 1940. A total of thirty-six attacks by U-boats resulted in zero sinkings. While it was concluded that the fjords in which some attacks were made caused a distortion in magnetic signatures of ships that would account for premature detonations, there remained the other failures outside the fjords, as well as the failures of the contact pistols. A thorough analysis of all torpedo attacks between January and June 1942, during which 816 torpedo hits were recorded, showed by extrapolation that the failure of the magnetic firing pistol had prevented the sinking of a very large number of ships in the early war years when conditions were most favorable for U-boat attacks. “As a result of torpedo failures the U-boat arm was robbed of great successes both in its operations against shipping and in its engagements with warships. Prematures undoubtedly led to the detection and destruction of attacking submarines.”The premature detonation of a torpedo shortly after being fired both alerted the enemy escorts and revealed the position of the firing boat, and, of course, the intended target was not hit.
Few things will affect morale more than a loss of confidence in weapons. Gunther Prien, the famous U-boat captain who sank a British battleship at anchor in Scapa Flow, stated it succinctly, “I could hardly be expected to fight with a dummy rifle.” Recognizing the danger, Donitz acted quickly and by dint of his personality and personal contact with the crews, he restored their confidence and fighting spirit. Interim adjustments in firing procedures were made, and by 1942, the problems themselves had been corrected.27 However, the real extent of the impact on the U-boat campaign will never be known; clearly, it was not insignificant.