Schepke’s U-100, damaged by the continuous attacks, soon caught up with the convoy. Although a surfaced submarine was immune to asdic, it was vulnerable to detection by radar, and despite the darkness he’d been detected a mile away by a primitive Type 271 radar set aboard the escort HMS Vanoc. A surfaced submarine, if spotted, did not have much time in which to dive to safety. This was Schepke’s predicament as Vanoc was suddenly seen accelerating to full speed. As she sped past HMS Walker, the escort commander ordered a signal made to caution her about speeding. He received the reply ‘have rammed and sunk U-boat’. By that time the shriek of the destroyer’s bow tearing through the steel U-boat came echoing through the night air. Schepke and the duty watch standing on the tower were all crushed and lost. Someone below gave the order to crash-dive but depth charges ripped the hull open and U-100 sank with all but seven of its crew.
While Vanoc was repairing its damage, and picking up German survivors, HMS Walker’s asdic showed another U-boat nearby, and then the set broke down. This brief encounter was with Kretschmer’s U-99. It was surfaced and heading home under cover of darkness. Kretschmer was below. On the conning tower there was the usual complement of four men: an officer, a petty officer and two ratings. Each man was assigned a quarter of the horizon to watch through his Zeiss 7×50 binoculars. Lighter, smaller and more waterproof than RN binoculars, such glasses were coveted by every Allied sailor who saw them. The officer occasionally swept the entire horizon: it was the routine. Suddenly they came upon the warships that had sunk Schepke’s boat. One of them was searching for survivors. One of the German lookouts on U-99 saw the moonlight reflecting off a gun turret: it was a destroyer about 100 yards away. Had they done nothing they would probably have escaped – standing orders said submarines sighting the enemy at night must stay surfaced – but the submariners were tired. Thinking he’d been seen, and contrary to orders, the officer on watch dived the U-99, and it was then that Walker’s asdic operator saw it briefly before his screen went blank.
The Walker’s depth charge attack had to rely upon skill, instinct and practice. Those first explosions brought Kretschmer’s damaged boat to the surface. Both destroyers opened fire. ‘With an understandable enthusiasm,’ rescued merchant seamen taken on board the Walker piled up so much ammunition around the guns as to cause confusion.
Kretschmer was forced back to the surface. All torpedoes expended and his boat crippled, he realized that his career was at an end, but his tonnage claims were foremost in his mind. He ordered his radio operator to send a message claiming 50,000 tons of shipping and telling Dönitz that he was a prisoner of war. When Kretschmer saw Walker lowering a boat he took it to be an attempt to capture his submarine. He sent his engineer officer to flood the aft ballast tanks so that the U-boat would sink stern-first. It reared up suddenly and steeply, and slid back into the ocean, leaving the crew swimming. When he climbed aboard the ship that rescued him Kretschmer still had his binoculars round his neck and wore the white-topped hat that had become a captain’s prerogative in the U-boat service. All but three of the U-boat’s crew were saved, but the engineer officer was one of those lost. Captain Macintyre, the escort commander, used Kretschmer’s Zeiss binoculars for the rest of the war.
Kretschmer, a prisoner aboard HMS Walker, remarked to George Osborne, her chief engineer, upon the coincidence that both ship and submarine had a horseshoe badge but one was the wrong way up. It was explained to him that in Britain a horseshoe pointing down is considered bad luck. An eyewitness said ‘it brought a rueful laugh from our prisoner.’
A destroyer was a cramped place, even without shipwrecked seamen and enemy prisoners aboard, and there was evidence of bad feeling. But the master and chief officer of J. B. White, a sunken merchant ship, and Otto Kretschmer an unrepentant Nazi, were persuaded by the chief engineer to join him in a game of contract bridge. Osborne said it was the only decent game he managed to get in the entire war.
Germany had lost her three U-boat aces and the Propaganda Ministry discovered that stardom for fighting men is a two-edged weapon. The loss of three ‘experts’ made Dönitz suspect that the British must have some new secret weapon. But then he changed his mind and decided it was just bad luck.
Dönitz had been right with his first guess. HMS Vanoc had used a primitive radar set, and in this same month, March 1941, a far more sophisticated 10-centimetre set was being tested at sea. It was the cavity magnetron which made such advanced radar possible and put the British work far ahead of the Germans. But in the summer of 1941 the range at which radar gave the first indication of an enemy’s presence was not always better than an alert observer could provide on a clear day. In May 1941 the pursuit of the Bismarck provided a better example of the contribution radar played in the naval encounters of that period.
When snatched from all effectual aid,
We perished, each alone:
But I beneath a rougher sea,
And whelmed in deeper gulfs than he.
William Cowper, ‘The Castaway’
The battleship Bismarck had been launched by the granddaughter of Germany’s great nineteenth-century German chancellor in February 1939. Commissioned in August 1940, it was the most modern and powerful battleship afloat, with eight 15-inch guns in four turrets controlled by the world’s best gun-laying radar.
Admiral Raeder’s original plan called for Bismarck and the heavy cruiser Prinz Eugen to sail from the Baltic, while the battleships Scharnhorst and Gneisenau would sally into the Atlantic from Brest in France. In mid-ocean this powerful force would rendezvous to form a fighting fleet powerful enough to sink convoys, and defeat any escort force they might encounter.1 This operational plan was code-named Rheinübung, Rhine Exercise, and Raeder saw it as a way of providing a big victory of the sort that ‘battleship admirals’ still cherished, while continuing the battle of the sea lanes that was obviously the key to victory. He knew that Hitler would invade Russia soon, and Rheinübung had to be staged before the army’s needs on the Eastern Front took precedence over everything the navy wanted.
Rheinübung was put under the command of Admiral Günther Lütjens, a bony-faced man with close-cropped hair and a permanent frown. The operation was thwarted when it was found impossible to have the Scharnhorst’s high-pressure turbine engines ready in time. Such engines were a notable and chronic failing in German marine engineering. Then, when Gneisenau was hit by a desperately brave attack by a Coastal Command torpedo aircraft in Brest Roads, Raeder decided stubbornly to go ahead using only Bismarck and Prinz Eugen. This plan too was delayed when Prinz Eugen was damaged by a British magnetic mine in the Baltic, thus losing the advantage of a month’s dark winter nights which would have made it much easier to slip past the Royal Navy.
In May 1941, Hitler was persuaded to make the trip to Gotenhafen (the now renamed Polish port of Gdynia) to inspect his new battleship and address the crew. That evening he dined with his senior officers aboard the Tirpitz. Hitler had doubts about the proposed expedition, but Admiral Lütjens reminded him of ‘Operation Berlin’. In the first three months of the year Lütjens had taken Scharnhorst and Gneisenau into the Atlantic, causing the British great anxiety as well as sinking 115,600 tons of shipping. He told Hitler that Bismarck was unsinkable. ‘Mein Führer, there is virtually nothing that can go wrong with a ship like this. The only danger that I can see is torpedo-aircraft coming at us from aircraft-carriers.’ This prophetic caution was due to Bismarck’s conservative design: its underwater protection had not kept pace with what was now considered essential for British and American ships.
For