Less than four months after the survivors of the Squalus were rescued, war had come again to Europe. As in the first World War, Great Britain and Germany were the principal antagonists on the Atlantic. Though at first forbidden to have submarines by the Versailles Treaty, Germany was later allowed to build them under a naval agreement with Britain signed in 1935. The agreement permitted Germany to have slightly less than half as many submarines as the British.
Almost as soon as the agreement was signed, Germany completed construction of its first submarines, and Britain cried foul, growling that Germany had built submarines in secret before the agreement was reached. The fact was, though, that German factories had stolen a march by prefabricating sections of U-boats. As a result, it was a matter of short work for German shipbuilders to complete a number of boats quickly when the agreement was actually signed.
By 1936 Germany had a total of twenty-eight new submarines in commission, but at that it was still far behind other major naval powers. Japan, for example, had more than sixty, and France had ninety-two. Soviet Russia had ninety-six.
When World War II began on September 3, 1939, Ge. many's submarine force had increased to fifty-seven boats (the United States at the time had fifty-five), but of Germany's fifty-seven, thirty-five were too small for anything but training duties and coastal patrolling. Even the largest of the U-boats were small in comparison with the French and British giants built in the 1920s and '30s, which displaced several thousand tons. Germany's largest submarine at the start of the war displaced only 740 tons, and its smallest — known as the "dugout" — displaced a mere 250 tons. In the course of the next five years Germany was to build hundreds of additional U-boats, but it never tried for great size, choosing instead to concentrate on large numbers of small, ma-neuverable craft.
In anticipation of hostilities, Germany's U-boat force was already at sea when the war began. At nine o'clock in the evening of the first day of war, Oberleutnant Lemp, in command of the U-30, sighted in the lens of his periscope a British passenger ship zigzagging on a course from the British Isles to America. Lemp attacked. His victim was the RMS Athenia of 13,500 tons. One hundred twenty-eight of its passengers and crew, including more than a score of Americans, were lost when it sank.
When news of the sinking was flashed around the world, Germany quickly denied that any of its submarines were responsible. The Germans countercharged that the liner had been sunk by the perfidious British — on specific orders from that archvillain, First Lord of the Admiralty Winston Churchill — in order to discredit Germany before the world. (Evidence which came to light after the war made it clear that at first German naval leaders had good reason to doubt that one of their submarines had sunk the Athenia. Orders given to U-boat commanders before they left on patrol had forbidden attacks on unarmed merchant or passenger ships, and no message telling of the sinking had been received at naval headquarters from any U-boat at sea. It was not until Lemp completed his patrol and returned to Germany on September 30, 1939, that Hitler and the German high command learned that it was the U-30 that had sunk the Athenia. After learning the truth they decided on elaborate measures to keep it a secret. The page in the U-30's war diary which covered September 3 was removed and replaced with a falsified one that made no reference to the sinking. Lemp was quietly court-martialed, convicted, and given a nominal sentence of one day's confinement in quarters. However, to prevent a repetition of such sinkings — which Germany knew might again in this war bring the United States in on the side of the Allies as it had in the last — orders were issued to U-boats which directed that no passenger ships were to be sunk under any circumstances, and the order remained in effect for almost a year.)
The first U-boat lost in the war was the U-39, and the events which ended with its sinking began with the premature explosion of three of its torpedoes. The action took place on September 14, eleven days after the war had started. One hundred fifty miles west of the Hebrides Islands off Scotland the U-39, under the command of Kapitanleutnant Gerhard Glattes, encountered the British aircraft carrier Ark Royal. Glattes maneuvered carefully into position and fired three torpedoes. Their detonators were of a secret type activated by the magnetic influence of a large mass of metal-such as the metal of a warship. However, Glattes's detonators exploded too soon and the aircraft carrier escaped undamaged.
The U-39 was not so lucky. British destroyers quickly found its position by following along a course determined by the place where the Ark Royal had been at the time the torpedoes would have hit, and the place where the torpedoes actually exploded. The destroyers' attack damaged the U-boat and brought it to the surface. Before it sank under British gunfire, Glattes and many of his crewmen jumped overboard. They were retrieved from the water and made prisoners by the British.
The unhappy experience of the U-39 was not unique. Faulty torpedoes became a plague to the Germans. One U-boat attacked the British warship Warspite five times in the Norwegian port of Narvik under perfect conditions, but because of torpedo failures it scored no success. The British cruiser Cumberland was actually struck by a torpedo which failed to explode, and the cruiser York was spared, like the Ark Royal, when three torpedoes streaking to destroy it exploded prematurely.
There were many other instances in which German magnetic-influence detonators either fired too soon or failed to fire at all. Impact detonators, which were supposed to explode the torpedo when it hit the side of a ship, often misfired too. A faulty depth control device added to the Germans' problems.
For a considerable period of time German ordnance technicians thought that it wasn't the torpedoes which were at fault. They accused the U-boat skippers of making inaccurate attacks, or blamed the torpedomen for improperly adjusting the torpedoes' mechanisms before firing. It was not until the summer of 1941, nearly two years after the start of the war, that the Germans developed a thoroughly reliable torpedo.
However, the loss of the U-39 was promptly avenged. The U-29, patrolling the same waters in which Glattes's U-boat had been sunk, came upon another British aircraft carrier, HMS Courageous. With more luck than Glattes had, Kapi-tanleutnant Schuhart of the U-29 fired a spread of torpedoes which reached their mark and exploded, sending to the bottom the first British warship of the war.
By the end of the first month of action, U-boats had sunk twenty-six merchant ships and a capital ship with a loss of two of their own number.
It was in the second month of the war that a German submarine was to undertake a bold mission, one of the most audacious of the war. The mission's objective was to slip into the heavily defended harbor of the great British naval base at Scapa Flow, Scotland. Scapa Flow was the Royal Navy's most important base, and it held bitter memories for the German navy — it was to Scapa Flow that the German high seas fleet was sent in defeat after World War I. Though the defenses of Scapa Flow were formidable, the Germans had learned from a spy in the Scottish town of Kirkwall, and from aerial reconnaissance, that a certain entry into Scapa Flow was not fully protected. The British had plans to block the unprotected entry at Kirk Sound by sinking an aging merchant ship in it, but the ship selected to be sunk was at first thought by the Admiralty to be priced too high and it refused to buy. When the original purchase price was finally accepted, it was then found that the price had been raised by the amount of the additional mooring fees that had accrued while the Admiralty and the owner haggled. After more delay the Admiralty finally bought the ship, and it began its journey from London to Scapa Flow at the end of a tow rope.
At the same time — October 8, 1939 — the U-47 under the command of Oberleutnant Gunther Prien, sailed from its base at Kiel to attempt the never-before-accomplished penetration of the Scapa Flow defenses. Like the blockship on its way north from London, the U-47 made for Scapa Flow's unprotected entry at Kirk Sound.
Arriving first, Prien planned to attempt his daring foray on the night of October 17 because that night there would be no moon. As it happened, though, the night was illuminated by a display of Northern Lights.
In the U-47 conning tower off the Scottish coast Prien put his powerful Zeiss binoculars to his eyes and peered into the semidarkness. The night wind blew biting salt spray into his face and onto the binocular lenses, and North Sea waves crashed against the U-47's dark hull. For long minutes the U-boat captain scanned the coast line.
For the last time he debated making the bold attempt which might well cost him his life. He weighed the factors. Somewhere on the bottom of the dark waters ahead of him lay the twisted and rusting wreckage of two U-boats which had tried to penetrate Scapa Flow's defenses in World War I and had been sunk in the attempt. The night was far from dark, which wasn't good. Still, there would always be a risk, and no night would ever be perfect. . . .
Prien made his decision. Calling down through the conning tower hatch, he gave the helm and engine orders that would take the U-47 in. Running on the surface because its submerged speed was not enough to counter Scapa Flow's strong tidal currents, the submarine followed a course that took it under the noses of the British defenders. At one point in the tense passage Prien found his submarine lighted up in the headlights of a car parked by the edge of the water. As Prien watched, the car quickly turned around and sped off ... to report sighting the U-boat?
But no British attack came. Passing through Kirk Sound, the U-47 slipped unchallenged into the inner fastness of the harbor of Scapa Flow itself and quickly submerged. Through his periscope Prien scanned the dark forms of ships before him. He chose the largest as the object of his attack. It was the British battleship Royal Oak. A single torpedo from Prien's first salvo struck it and exploded. Oddly, there was no apparent alarm among the ships in the harbor. Evidently the explosion was thought to have been caused by explosives inside the British ship.
The U-47's torpedomen trundled a new salvo into the submarine's tubes. Again the order to fire was given and this time several hits were made. At once the night was pierced with the beams of searchlights and the sound of gunfire. Almost immediately the Royal Oak went to the bottom. In the ensuing chaos of churning ships and of guns blazing at phantom targets, the U-47 slipped out of Scapa Flow as easily as it had slipped in.
When they reached Germany Prien and his crew were lionized. Decorations were presented to all, including Germany's highest honor to the captain himself.
Three days after the U-47's raid the blockship tardily arrived from London and was sunk across the route the U-boat had taken. No German submarine ever again penetrated Scapa Flow's defenses.
By the summer of 1940, after less than a year of war, rampaging submarines had sunk 2½ million tons of Allied shipping. However, British antisubmarine measures were gaining in effectiveness, and for a time U-boat losses exceeded replacements.
Nevertheless, the balance of the battle was decidedly in favor of the submarines. Attacking at night and on the surface, they struck at convoy after convoy. Their greatest single success of the war came in the fall of 1940 on the night of October 18-19 — which came to be known among German submariners as their "night of the long knives." On that night Germany's three top U-boat aces — Gunther Prien in the U-47, who a year before had penetrated Scapa Flow, Otto Kretschmer in the U-99, and Joachim Schepke in the U-100 — waded into two separate convoys. When day dawned they had sunk thirty-two out of eighty-three ships.
(Less than six months later the German submarine service suffered its most memorable losses of the war when in a period of nine days the British sank the three U-boats from that "night of the long knives." Of the three aces, only Kretschmer survived, to be taken prisoner. He is today a senior officer of the West German navy.)
By June, 1941, Admiral Karl Doenitz, commanding theGerman submarine force, was able to send a total of thirty-two U-boats on patrol at once — up from a maximum of six in the early months of the war. With thirty-two submarines at sea Doenitz put into operation a technique which he had conceived during the lean years after World War I (in which he himself had served as a U-boat captain, commanding the UB-68 until it was sunk and he was captured). The German admiral called his technique die rudeltaktik, meaning the flock or group tactic. It employed a number of submarines in coordinated attacks on shipping. To the Allies such flocks or groups of attacking U-boats became known as wolfpacks.
The advantages of the rudeltaktik were several. It permitted U-boats to make organized rather than piecemeal attacks. It caused defending forces to be spread thin in the attempt to deal with a mass attack, and prevented them from concentrating their efforts against lone submarines as they would in the case of independent attacks.
Moreover, with a rudel of submarines scouting, convoys could be located more easily. Once a convoy was located, the wolfpack would assemble — and many a lonely radio operator in an Allied merchant ship came to know the chilling sound of U-boat radios broadcasting from many points of the compass as they exchanged coded information and closed in for the attack.
The senior and most experienced U-boat captain would direct the attack, which would be made at night with all submarines operating at top speed on the surface, their decks just awash. Knifing among the ships of the convoy the U-boats would fire torpedoes at ship after ship.
In minutes the eerie darkness would be ablaze with burning oil from stricken tankers. Adding to the illumination was the pallid light of star shells from destroyers. Arching outward from the attacked ships were the streaks of tracer shells as they probed for U-boats.
Left behind at the end of the action as the surviving ships sailed on and the submarines submerged would be groups of oil-drenched survivors bobbing on the dark sea. Their chances of rescue were slim.
Such was the grim heyday of the U-boat, a heyday that was to see many successes before the tide of war turned.
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