From The Germans in Normandy, by Richard Hargreaves (Pen and Sword, 2006), Kindle Loc. 4146-67:
Frustration on land was mirrored by frustration at sea and in the skies. Across France in the first week of August there was a growing realization in the mind of the Landser [soldier], Matrose [sailor] and Flieger [airman] that the house of cards was about to collapse, that the efforts of the summer of 1944 had been in vain. The Kriegsmarine’s campaign against the invasion armada had been an unmitigated disaster, despite Karl Dönitz’s attempt to hide the fact with his continued exhortations:
Two years ago it was fair to say that Norway had to be defended in American waters where we could sink the most shipping. Such a concept is no longer applicable. Today it is more important to sink one landing ship in the invasion area than it is to sink one Liberty ship in the Atlantic, for example.
The problem was that Dönitz’s U-boats could get nowhere near the invasion fleet. The Allied defensive blockade was impenetrable. ‘The very strong defences encountered in the Seine Bay are striking,’ the admiral complained. ‘U309 had to return after only six days’ operations in the invasion area because of the utter exhaustion of her crew.’ Herbert Werner’s U415 too lasted just six days, another victim of enemy counter-measures – an aerial mine dropped outside the imposing U-boat pens at Brest. Werner had sunk no enemy vessels. In return, he lost his boat and two of his crew. Its loss, Werner bemoaned, ‘became just another statistic in the dismal obliteration of our U-boat force’. In the first fortnight of July, thirteen U-boats had been lost, leaving just six submarines to challenge the invasion fleet. ‘During these disastrous two weeks, no more than three or four U-boats at a time were attacking the convoys ferrying invasion supplies,’ Werner wrote. ‘New Allied divisions, fully equipped and with thousands of tanks and vehicles, poured ashore.’ As he buried his dead in the cemetery of a Brest suburb, Werner found himself pondering his fate. ‘What could I say to parents who, if their sons must die, wanted them to die as heroes in combat?’ he asked himself. ‘I was still struggling with my sentences long after midnight.’
Karl Dönitz had made no rash promises on behalf of his navy in the event of invasion. His men would do their duty, but he had never assured Hitler they could halt an enemy armada. Hermann Goering, on the other hand, had pledged his Luftwaffe would give its all, that it would fight itself to death in achieving victory in the west. And now, two months after the invasion, the Allies had a firm foothold on French soil while the German air force was heading for oblivion. It could not make good its leader’s promises.