German U-Boat

Donitz had long wanted to penetrate the defenses of Scapa Flow and deal the Royal Navy another stinging blow. The Admiral conceived a plan within days of the war itself which encompassed a two pronged assault on the Royal Navy. The first called for a U-boat attack within the base itself, which if successful, would force the British Home Fleet to flee the base to relocate to safer harbors. Consequently, the withdrawal would weaken British blockade over the North Sea, making it less hazardous for German surface raiders. The second strategy Donitz plotted was for the Royal Navy to disperse to other anchorages until Scapa Flow could be made secure again. Prior to the mission, Donitz ordered for mines to be laid in the three most likely refuges – Scotland’s Loch Ewe, Firth of Forth and Firth of Clyde, where he hoped to bag any retreating ships into a barrage of minefield.

Donitz studied intelligence information gathered on Scapa Flow. Luftwaffe aerial photographs taken on September 6 showed the British defenses - the blockships amid steel nettings outlining the bay’s seven entrances. It also showed the entire British Home Fleet at anchor. Between 13 and 29 September, U-14 supplemented further intelligence by scouting perimeter defenses around the Orkneys and measuring tidal conditions. The Admiral conceded, that a penetration had to be done on the surface, at night and during high tide when the current was weakest. The path to be taken was through Holm Sound at the eastern end, and then Kirk Sound, navigating through the sunken blockships and through into Scapa Flow. Kirk Sound itself was only five hundred meters wide, and 15 meters deep at its deepest. The deepest path of the channel was blocked by three sunken blockships while a fourth lay on the side further obstructing any straight passage attempts. With the deepest paths obstructed, the gap was now narrowed to 170 meters, but most of these were impassible as it was too shallow at three meters and less (as the water recedes to shore). The U-boat had to pass right next to the blockship where it was seven meters deep. Steering off course would either result in a collision or the U-boat being beached on the shore.

Having decided his approach, only one thing remained – finding the right skipper to undertake such a mission. He had to possess excellent skills and the guts to take on a bull by its horns. The man Donitz deemed to possess such personal qualities was Lieutenant Commander Gunther Prien.

Prien, aged 31 was an excellent commander and in the U-47, a Type VIIB, he had already sunk three British merchants with a total of 66,000 tons during his first war patrol. Having already won the Iron Cross Second Class, Prien was an outstanding seaman with a deceptively daring thrust. An American journalist who met him in Berlin described Prien as “clean-cut, cocky, a fanatical Nazi and obviously capable”. But Prien would later be recognized as one of the greatest U-boat aces in the annals of naval history.

October 1st, 1939. Codenamed “Operation Order North Sea Number 16”, Donitz briefed the mission orders to Prien. The penetration was scheduled for the night of October 13/14, where the tide would be the highest this time of the year. It was to be a moonless night on Friday the 13th. Departure would be the preceding Sunday, on October 8th, or one week from the date of his briefing. U-47 would unload all sensitive equipment, including the ENIGMA, secret papers, and all non-essential provisions. It was to maintain absolute radio silence, penetrate the British base with explosives already rigged and ready to scuttle at moments notice; to prevent capture of the U-boat or its equipment. Even the existing steam powered torpedoes, the G7a were to be unloaded and replaced with a new top secret weapon – the wakeless, electrically powered G7e torpedo. The British had no knowledge that German scientists had successfully developed an electrically powered torpedo. U-47 would operate as a lone wolf, in utmost secrecy and all existing boats around the Orkney islands would be withdrawn to maintain the clandestine nature of the mission. Even Grand Admiral Raeder was briefed verbally by Donitz to prevent from information leaks.

Much was at stake, and the Admiral gave Prien 48 hours to make his decision whether to accept or not – as he saw fit. He was handed with all documents for his study of the mission details and by nightfall, Prien had already made up his mind.

Two days later, on Tuesday October 3rd, Prien was summoned into Donitz’s office. “Yes or no?”, the Admiral asked, to which Prien replied “Yes sir”.

As if sealing the fate of the mission, Donitz stepped forward and shook his young commander’s hand, “Very well. Get your boat ready.”

Next: Foray into Scapa Flow