Almost a year earlier a young U-Boat captain had shocked the Royal Navy with his daring raid into their deep water anchorage at Scapa Flow. Gunther Prien had returned to Germany a national hero.
His activities were celebrated in the German press, much as they might follow a film star. Amongst those closely following the story was Royal Navy Intelligence.
Many U-boats patrolled without much success. But, for the moment, the Kriegsmarine had a small group of talented and highly motivated U-Boat captains who were determined to sink ships – and they were becoming very successful at it. They rivalled each other in a league table of ‘tonnage sunk’. Together they were rapidly becoming a threat to Britain’s ability to carry on the war. If every U boat had been as successful as Prien in September 1940 Britain really would have been in trouble.
September Cruise of Kapitanleutnant Prien
After six weeks in Germany, Prien carried out a cruise lasting approximately 28 days:
He started operations by sinking the Belgian Ville de Mons on the 2nd of the month, N.E. of Rockall. Proceeding westward he sank the British Titan on the 4th when N.W. of Rockall, and it is thought that he then fell in with convoy S.C.2, … sinking on the 7th the Norwegian Gro and two British ships, the Jose de Larrinaga and the Neptunian. Following the convoy south-eastwards towards Ireland until after dark on the 8th, he sank two more British vessels, the Poseidon and the Mardinian, about 100 miles N.W. of Malin Head.
If this cruise has been correctly estimated as set out above the total tonnage sunk was 37,441. Prien claimed 46,250. It is perhaps relevant to recall that he has so far managed to out-distance any competitors’ claims.
October 1940 Naval Intelligence Bulletin