German U-Boat

On Sunday, 8 October 1939, U-47 discreetly departs Kiel harbor. There was no ceremony, no cheering crowds, only the customary salute and well wishes. Those in Germany, including those in the higher chain of command were oblivious to the mission. Even the crew had not been told where they were heading.

The four days journey to the Orkneys would be a slow and an uneventful one. To remain undetected, Prien traveled on the surface by night, submerged when a ship was sighted, and remained submerged during the day. The crew was baffled at their captain’s actions, but nobody said a thing.

By the evening of 12th October, U-47 arrived to within 1.8 nautical miles off from the Orkneys. Lying safely bedded on the bottom, Prien gathered his forty men crew and briefed them the nature of their mission. “Tomorrow, we shall enter Scapa Flow”, he said in his characteristic staunch voice. No one expected them to survive, but he was confident they would succeed. Although the mission was fraught with danger and the risk of death was great, all hands were enthusiastic. An eerie silence followed, indeed the only sound was the dripping of water on the metal floor, and the occasional creak of water pushing against the hull.

The rest of the day was spent waiting at the bottom. The men went to their bunks, the lights extinguished as they waited for night to fall on the 13th. Those that could get some sleep, did so. At 4pm, a lavish dinner was served. The crew jokingly referred to it as the “hangman’s dinner”. At 5pm, the torpedoes were checked, scuttling charges laid and by 7pm, they were ready to go into Scapa Flow. Finally at 7.15pm, on the moonless night of October 13 1939, U-47 surfaced for the approach.

As Prien climbed onto the conning tower, the view was not what he had expected. Instead of finding the darkness he craved, the horizon was disgustingly bright. The sky was ablaze with the shimmering glow of the Northern Lights - as if like a bonfire. For a moment, he hesitated, but pressed on anyway, planning if necessary to carry out the attack submerged. For the next four hours, the U-47 worked its way to Scapa Flow.

Approaching Holm Sound, at 11.07, the bridge watch spotted a merchant trodding along. Prien dived to avoid detection and just for sizing up, placed the merchant in the crosshairs of his periscope. Despite the glittering horizon, he could not see the ship. A submerged attack was out of the question. He would have to attack from the surface.

Prien surfaced at 11.31, fixed his position and then headed for Kirk Sound, and onto the gap between the blockships. As he aimed for the fifty five foot gap between the Thames and Soriano blockships, the fierce tide swept the U-boat, at what he described as an “unbelievable speed”. His approach towards the gap had not been perfect. Suddenly, Prien spotted wire cables, one as thick as a foot and several as thick as six inches running across the hulks. These cables were the anchoring lines that held the blockships in place. The current was too strong to turn back, so Prien steered for the center of the gap, hoping to ride over the cables that stretched beneath the surface.

As the keel bottom struck the cables, the sound of scraping metal reverberated through the hull. The crew wondered if they had fouled a mooring mine, and that they could be blown to bits at any moment. Nevertheless, the U-boat scrapped over the cables and the sound stopped. But as a result, the contact jostled the craft to the right and it bumped the seabed and ran aground.

Prien tried maneuvering with a combination of rudder and engine, but it would not dodge. If he was still stuck at dawn, the U-47 along with its crew would belong to the British. Prien approached the channel with his ballast tanks partially flooded, so as to stay low in the water, reducing its silhouette. Now he ordered to blow all ballast tanks, and to the relief of the crew, the U-boat finally floated free of the sandy coast. Prien immediately banked hard to port to steer her back into the current. After steadying his boat, the channel gradually widened, the current slowed, as the U-47 sailed into the dark openness of Scapa Flow.

As the boat exited the channel, the crew could see shoreline activity just a few dozen meters away. Enhanced by the undulating Northern Lights, they could make out sentry guards and trucks parked along the shore. But suddenly the conning tower of the U-boat was illuminated by the headlights of an automobile. The crew was alarmed, thinking that they had been spotted and machine gun bullets would pelt the conning tower at any moment. But as abruptly as the light had appeared, it faded away as the automobile turned around and sped off. Prien continued his operation.

The time was twenty seven minutes past midnight on 14 October. A new log entry was recorded, “Wir sind in Scapa Flow!” (“We are in Scapa Flow!”).

Visibility was extremely good. Prien, his first watch officer Engelbert Endrass, and the lookouts hungrily scoured the surface, expecting to find the British Home Fleet looming on the horizon. U-47 cruised westwards for another three and a half miles - no ships were in sight. He turns back and sails eastward, almost reaching Kirk Sound, the original entry route. Still nothing. By now the U-boat had been circling for more than 30 minutes. The excitement and euphoria of the hunt had turned to bitter disappointment. A terrible mistake had been made. The British Home Fleet was not home. Astounded that not a single warship was found, Prien wondered, had they crept all the way across and into the lion’s den to find no one home? What happened to the array of ships anchored in Scapa Flow, as suggested by intelligence reports?

Unbeknownst to Prien and his crew, the British Home Fleet had sortied into the North Sea and most of the big ships had left Scapa Flow by October 13, the day designated for the attack. On the fateful October 8th, the day when U-47 departed Kiel, the Kriegsmarine’s new battle cruiser Gneisenau and light cruiser Koln had also set sail on a brief sortie into the North Sea. Their mission was to lure the British Home Fleet out from their bases into range of Luftwaffe aircraft. As intended, the British got wind of the sortie and believing Gneisenau was headed for the North Atlantic, Admiral Forbes ordered the Home Fleet to intercept her. But Gneisenau retreated back into Kiel, after having lured the Home Fleet into range of German aircraft. On October 9, the Luftwaffe found and attacked the British fleet with over a hundred bombs – but there was not a single hit.

Unaware that Gneisenau had returned to Kiel, the British continued the hunt further north of the Orkneys. Finding no trace of the German fleet, Admiral Forbes finally broke off the search. The battleships Nelson and Rodney, battle cruisers Hood and Repulse and the carrier Furious which had sailed from Scapa Flow, retired to Loch Ewe in western Scotland. Thus the Gneisenau sortie did nothing but to empty Scapa Flow of the major capital ships. Only the old 29,000 ton battleship Royal Oak, remained in Scapa Flow. She was left out of the Gneisenau hunt as her top speed of 20 knots was too slow to keep up with the modern fleet. Still, she was slated to depart Scapa Flow the following morning. Just two days earlier, a Luftwaffe reconnaissance plane was spotted flying low over Flow. The British fearing that this was prelude to a bomber attack, decided to keep the base empty for a while.

Next: Attack on the Royal Oak