The overwhelming superiority achieved by the enemy defence was finally proved beyond dispute in the operations against the next two convoys, SC 130 and HX 239. The convoy escorts worked in exemplary harmony with the specially trained ‘support groups‘.
To that must be added the continuous air cover, which was provided by carrier-borne and long-range, shore-based aircraft, most of them equipped with the new radar. There were also new and heavier depth charges and improved means of throwing them. With all this against us it became impossible to carry on the fight against convoys.
It was only bit by bit that I received definite details of the losses we had suffered in the action against these two convoys and among the boats on passage, particularly in the Bay of Biscay, off Iceland and the focal areas in the North Atlantic.
Losses had suddenly soared. By May 22 we had already lost thirty-one U-boats since the first of the month, a frightful total, which came as a hard and unexpected blow; for, notwithstanding the very much more powerful enemy anti-submarine forces in operation in this fourth year of war, an increase in U-boat losses had not until this moment been perceptible.
Since the beginning of 1943 U-boat operations had been concentrated more and more against convoys. This is reflected in the ratio between total sinkings and sinkings of ships in convoy.
In the first half of 1942 ships in convoy represented 39 per cent of the total sinkings; in the first three months of 1943, however, the figure rose to 75 per cent. Operations against convoys are nevertheless much more difficult and more dangerous than attacks on solitary ships in far distant waters.
Yet, in spite of the fact that the number of U-boats detailed to work against convoys had been vastly increased, the losses incurred rose only slightly from 8.9 per cent to 9.2 per cent and they certainly constituted no warning indication of the sudden soaring of the rate of losses which we now experienced.
In the submarine war there had been plenty of setbacks and crises. Such things are unavoidable in any form of warfare. But we had always overcome them because the fighting efficiency of the U-boat arm had remained steady.
Now, however, the situation had changed. Radar, and particularly radar location by aircraft, had to all practical purposes robbed the U-boats of their power to fight on the surface. Wolf-pack operations against convoys in the North Atlantic, the main theatre of operations and at the same time the theatre in which air cover was strongest, were no longer possible.
They could only be resumed if we succeeded in radically increasing the fighting power of the U-boats.
This was the logical conclusion to which I came, and I accordingly withdrew the boats from the North Atlantic. On May 24. I ordered them to proceed, using the utmost caution, to the area south-west of the Azores.
We had lost the Battle of the Atlantic …