Military history

A DRAMATIC RECONVERSION

Long in gestation and birth but as yet unformed, the new German submarine force required a skilled leader. Raeder, as he wrote, had not a shadow of doubt about the man for the job. His choice was Karl Dönitz, a forty-eight-year-old junior captain who epitomized Raeder’s efforts to create a loyal, dedicated, responsible, professional naval officer corps.

The younger of two sons of Emil Dönitz, an engineer with the Zeiss optical firm, Karl Dönitz was born September 16, 1891, in Grünau, a suburb of Berlin. His mother, Anna (nee Beyer), died before he was four years old. His father, who never remarried, raised the two boys, Friedrich and Karl, in Grünau and in Jena, near the city of Weimar. They lived in middle-class comfort in an all-male environment; the boys received a classical education in private schools. Although there was no maritime tradition in the family, Friedrich joined the merchant marine and on April 1, 1910, at age eighteen, Karl joined the Imperial Navy. The father died two years later; the brothers drifted apart and ultimately became estranged. For Karl, the Navy was to be both family and career.

The career went well. After a mandatory year at sea as a cadet on the training cruiser Hertha, and a year at the Imperial Naval Academy in Mürwik, Dönitz won a commission and in 1912 was assigned to the new light cruiser Breslau, operating in the Mediterranean and Black seas. Upon the outbreak of the war in 1914, the Kaiser turned over the Breslau and a battle cruiser, Goeben, to Turkey as quid pro quo for entering the war on the side of the Central Powers. Sailing with mixed German-Turkish crews, the two ships conducted cat-and-mouse operations against the Czarist fleet in the Black Sea. During Breslau’s refits, Dönitz qualified as an aircraft observer, married Ingebord Weber (May 27, 1916), daughter of a German general stationed in Turkey, fathered a daughter, Ursula (1917), and published a stirring book about his shipboard adventures, The Voyages of the Breslau in the Black Sea.

When, in 1916, the Imperial Navy shifted its main emphasis to U-boats, Dönitz volunteered. After a three-month training course in Germany, he returned to the Mediterranean in early 1917 to serve as a watch officer on U-39, commanded by Walter Forstmann, Germany’s second-ranking U-boat “ace.” From February to October 1917, Dönitz made four war patrols on U-39, during which Forstmann sank thirty-two ships. Promoted to command UC-25, a small, old minelayer, Dönitz made two more war patrols in the Mediterranean, during which he laid two minefields and torpedoed five ships—and won a high decoration for bravery, the Knight’s Cross of the House of Holhenzollern.

In the closing days of the war, September 1918, Dönitz was promoted to command a larger attack submarine, UB-68. On October 4, while on his first patrol in the Mediterranean, he attacked a convoy and sank a ship. But in the ensuing action, the U-boat went out of control and popped to the surface. Under heavy fire from the convoy escorts and unable to dive, Dönitz was compelled to scuttle. The British fished Dönitz and twenty-nine others from the water and took them to England, where they remained imprisoned until July 1919.

When Dönitz rejoined his wife and daughter in chaotic postwar Germany, he elected to remain in the Reichsmarine. For the ensuing four years, 1920-1924, he commanded a destroyer, T-157, at the naval base Swinemünde, on the Baltic, where the Dönitz family expanded with the birth of two sons, Klaus (1920) and Peter (1922). Following that tour, Dönitz, promoted to lieutenant commander, was assigned to the naval staff in Berlin, where he served under Rear Admiral Erich Raeder.

Raeder was favorably impressed. In one official assessment, he wrote that Dönitz was a “smart, industrious, ambitious officer” who possessed “excellent professional knowledge” and expressed “clear judgment in questions of naval war leadership” and had “good military as well as technical gifts.” From 1928 onward, Raeder guided Dönitz to ever higher rungs on the career ladder: promotion to full commander and command of a destroyer (half) flotilla, 1928-1930; First Staff Officer of the North Sea High Command, 1930-1934; promotion to junior captain and to the coveted job of commander of the light cruiser Emden, 1934-1935.

Karl Dönitz was not pleased with his assignment to U-boats. The emphasis in the Kriegsmarine was the buildup of a big-ship surface navy. Submarines were clearly secondary and restricted by the terms of the Anglo-German Naval Treaty. He felt he had been “pushed into a backwater” and that his promising naval career had possibly reached a dead end.

But a dramatic reconversion occurred. After plunging into his new job with “all the energy at my command,” as he put it in his memoirs, “body and soul I was once more a submariner.” The reconversion led to a single-minded conviction: that notwithstanding Hitler’s grand strategy, war with Great Britain was inevitable and that Germany should be building not big surface ships but submarines—hundreds of submarines.

This conviction derived from a close study of German U-boat records, official and unofficial naval histories of World War I, and his own U-boat experiences. In his view, the small, primitive Imperial Navy U-boat force had come very close to imposing a war-winning maritime blockade against Great Britain. Had Germany built large numbers of U-boats rather than big ships for the High Seas Fleet, and had the Kaiser authorized unrestricted U-boat warfare in the first year of the war, Dönitz concluded, Germany could have achieved an early and decisive naval victory over the Allies. With proper organization and planning and modern submarines and new tactics, he believed victory could be realized in the war he saw coming.

To be sure, there would be difficulties and hazards. First, convoys. Convoying saved the Allies from defeat at sea in World War I. This time around the Allies were certain to form convoys in the early days of the war. Second, sonar. The Reichsmarine knew the Royal Navy had developed an active electronic underwater detection device, which the British believed to be 80 percent effective at locating submarines. Third, aircraft. Reliable, fast, modern airplanes could search huge ocean areas and carry a greater payload of improved ASW bombs and depth charges.

Even so, Dönitz believed the submarine could win. This conviction was based on the significant technological advances German engineers and other specialists had achieved in submarine construction, torpedoes, and communications, and on a new tactical doctrine German submariners conceived for attacking convoys.

The new U-boat prototypes were far superior to the U-boats of World War I. Built of a new steel alloy, which was welded rather than riveted, they were tougher and more maneuverable, and dived much faster and deeper. The new medium (500-ton) boat had twice the diesel and electric horsepower of its predecessor, giving it 3 knots greater surface speed (16 versus 13) and the ability to accelerate rapidly to full speed when submerged. The surface cruising range of the new boats could be greatly extended by an ingenious fuel-conservation technique, wherein one of the two diesels could be rigged to turn both propeller shafts.

German engineers had produced what were believed to be marvelous improvements in submarine torpedoes. The warheads were nearly double the size of the World War I model (612 pounds of explosives versus 352 pounds). In addition to the “air”-propelled torpedoes, the Germans had perfected a torpedo propelled by electricity (from storage batteries), which left no telltale wake pointing to the submarine. As another measure to conceal the position of the submarine, the submarine torpedo tubes had been redesigned to absorb the bubbles created by the compressed air used to eject the torpedo. All torpedoes could be fitted with a “magnetic” pistol (or fuse) that was activated by the magnetic field of the target. Designed to explode beneath the keels of the targets rather than against the sides, magnetic torpedoes were deemed to be much more lethal than torpedoes with impact pistols. It was possible that only one magnetic torpedo would be required to sink an enemy ship.

Radio technology had also greatly improved since the last war. The new U-boat prototypes were equipped with a superb array of receivers and long- and shortwave transmitters. Hence a force commander could maintain clear and continuous contact with all U-boats at sea, and the boats could communicate with one another. This communications linkage enabled a force commander to receive and relay reports on enemy positions, to receive current reports from U-boats on damage inflicted on the enemy or damage sustained and the type and extent of enemy ASW measures, to know the amount of fuel and torpedoes remaining on board each boat at any given time, and to know the current weather and sea conditions in the assigned operating area.

In World War I, U-boats had failed against enemy convoys because they could seldom find them and when a U-boat did find one, it usually had to attack alone. Dönitz believed that enemy convoys could now be located by a more sophisticated deployment of U-boats on likely convoy routes, by Luftwaffe aerial reconnaissance, and by intelligence on enemy convoy routing derived from codebreaking, spies, and other sources. Upon receiving information on the composition, course, and speed of a convoy, Dönitz postulated, a force commander could in theory shift the available U-boats by radio to positions to intercept the convoy for a massed or group attack, which the confused escorts would be virtually powerless to prevent.

The group (or “wolf pack”) attacks could be carried out either in daytime while submerged or at night while on the surface. To minimize detection in submerged daylight attacks, the U-boats were to employ only wakeless battery-powered (“electric”) torpedoes, with magnetic pistols in the warheads. In night surface attacks, when torpedo wakes were harder to see, the faster, longer-range “air” torpedoes with magnetic pistols were to be used.

Dönitz thought the new ASW weapons, namely sonar and aircraft, were greatly overrated. The most advanced sonar still had serious technical weaknesses, a range of one to one and a half miles at most, and—most important—it could not detect a submarine on the surface. The electric torpedoes had a greater range (three miles) than sonar. Hence, in the initial daylight submerged attack, a U-boat could “stand off’ and shoot before there was any possibility of being detected by enemy sonar. Should a hunting escort make sonar contact with the submerged U-boat after the attack, the U-boat could evade and escape with its rapid acceleration and deep diving. Aircraft could not usually see a submerged submarine or its periscope in most waters and thus posed small to no danger to a U-boat using wakeless torpedoes during a submerged daylight attack. Aircraft did not yet patrol at night; hence none would be present during a night surface attack. The principal danger posed by an aircraft was its ability to detect a submarine traveling on the surface in daylight. But aircraft were still relatively slow. A keenly alert U-boat bridge watch, Dönitz believed, could see or hear the aircraft before it saw the U-boat. With its ability to dive quickly (thirty seconds) and deep, a properly alert modern U-boat could avoid attack by any known aircraft.

To win the commerce war, Dönitz calculated, Germany would require a force of about 300 medium (500-ton) U-boats. Counting time lost going to and from the combat zone and time lost in refit and overhaul, this number would enable Germany to keep about 100 U-boats in the convoy hunting grounds. Based on the results achieved by the U-boats of World War I, Dönitz calculated, a force of modern boats could doubtless sink a million tons of British shipping a month. The British merchant marine of the late 1930s comprised about 3,000 ships of 17.5 million tons, including tankers. Thus, in a mere six months, U-boats could destroy almost one-third of it, and within a year, almost two-thirds. It therefore appeared reasonable to Dönitz that a modern German U-boat force could throttle the British in a year or a year and a half.

Early in his new job, Dönitz informally submitted these ideas to Raeder and to the Berlin naval staff, the Oberkommando der Kriegsmarine (OKM). He was sternly rebuffed. Hitler had assured Raeder, time and again, that war with Great Britain was unthinkable. As historian Ruge wrote, war games with Great Britain as the enemy were prohibited. The Anglo-German Naval Treaty—Hitler’s great diplomatic triumph—had just been signed. Under the terms of that agreement Germany was restricted, except in unusual circumstances that required renegotiations, to about 24,000 tons of submarines. By then most of the permitted tonnage had already been allocated. Even if it had not been, the entire allowance would produce merely forty-eight medium (500-ton) boats. Besides that, Germany had agreed to sign the Submarine Protocol, which barred surprise attacks on almost all merchant ships. Moreover, many senior officers at the OKM were unshakably convinced that sonar and modern aircraft had ruled out the possibility of submarine warfare in the hunting grounds close to the British Isles. They had proposed larger submarines for operations in distant waters where enemy ASW measures were less intense. These boats were to raid enemy (i.e., French) maritime assets, in a manner similar to the “pocket” battleships and armed merchant cruisers, adhering to the “cruiser rules” and the Submarine Protocol.

Dönitz was neither discouraged nor dissuaded. He remained absolutely convinced that sooner or later Hitler would provoke war with Great Britain; that it was a grave mistake for the Kriegsmarine to build big surface ships; that the Anglo-German Naval Treaty, the submarine tonnage limitations, and the Submarine Protocol would be abrogated; and that Germany would be compelled for the second time to turn to U-boats for waging war at sea. He therefore did everything in his power to shape the training, weaponry, and operational planning of the new U-boat force to fit his convictions.

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