One could hardly doubt, in March 1943, that the Battle of the The Atlantic had not reached its apogee and that, in the three or four months which would follow, one of the two adversaries had to slide towards defeat. Admiral Donitz was playing his last cards. Its fleet included 240 submarines. He concentrated no less than 112 in the North Atlantic. Intoxicated by their success and highly trained, the commanders of these submarines were able, by the very nature of the battle, to dictate the terms. Almost without exception, U-Boat packs were concentrated in areas where air escorts could not operate. This is where they collected most of their sinister booty.
In March, the aircraft carriers, finally released from their mission towards the convoys of Operation "Torch", were returning to the Atlantic with the protection groups. We could finally hunt submarines there and overcome them. At the same time, two other events made a notable contribution to the battle. Using his authority as commander-in-chief of the American forces, President Roosevelt added his contribution by delivering his Liberator plane, which had a very large field of action. At the end of March, about twenty of these planes were operating in the North Atlantic. By the middle of April, the number of these devices had risen to 41. This was still too few to cover basic needs, but it was at least a promise of improvement.
The other contribution was made by scholars. They had just created a small-wave radar that could detect much smaller obstacles and against which the receivers, with which the German submarines were equipped, could not do anything. Many surface escorts were equipped with it towards the end of 1942 and the beginning of 1943. It was to allow much better contact with the submarines and had the added advantage that the latter no longer knew that they had been detected. . This new radar could also be attached to aircraft, but other priorities in the R.A.F. slowed its rise to Coastal Defence.
At the beginning of May, another gigantic convoy battle was fought. It provides the first opportunity to test the effectiveness of protection groups and discontinuous air escorts. A convoy was delayed and somewhat scattered due to a violent storm south of Greenland, a region known for its high concentration of submarines. A pack of 12 of them gathered around the convoy. This was the kind of situation for which the protection groups had been formed. Two of these groups were dispatched from the port of Saint John, Nova Scotia, as the convoy approached the danger zone. They too were delayed by the storm which had dispersed the convoy. Before their arrival, the submarines had already sunk 5 ships during the night, and 4 more the following day. One of the convoy's escorts, the corvette Pink, had nevertheless attacked and sunk U-192.
The two groups joined the convoy the same evening and, for the first time, the U- boote were met with the full application of new Allied countermeasures. As the convoy regrouped after being shaken by the storm, the submarines renewed their attack. But each of them was detected and removed before they could cause any damage to the merchant ships. HMS Loosestrife spotted U-638, chased it and sank it. The Destroyer. Vidette spotted the U-125, thanks to her asdic, hit it with a “hedgehog” blow and sank it. Oribi rammed U-531 and destroyed it. As for the pelican scout, it detected the U-438 which it quickly overcame. The planes operating above the convoy got the better of 2 other submarines:the U-710 destroyed by a Coast Defense aircraft and the U-630, by a Royal Canadian Air Force plane. But the cut was not yet full for the Germans because, in the darkness, the two submarines U-659 and U-439 had to collide and both sink.
The defeat was severe for the U-boats. A defeat during a campaign does not necessarily mean victory for the other side. However, the fate of the convoys that followed was to prove, in fact, that this victory was not a flash in the pan. The following convoy lost 3 of its elements but it cost the enemy 3 of its submarines. The slow convoy which was passing at the same time, lost 2 of its ships while 2 U-boats were sunk and some others were seriously damaged. Of the two convoys that followed, the result was even more dramatic. The slow convoy reached England with no casualties, but in its wake lay the broken hulls of U-954, U-258, U-209, U-273 and U-381. The fast convoy also arrived intact, but U-752 had joined its brethren at the bottom of the Atlantic.
Even more impressive, however, were the figures from April to July. In April, when the whole new escort system on the surface and in the air was barely gaining momentum, the submarines sank 245,000 tons of Allied shipping and lost 15 of their elements. In May, they sank 165,000 tons against a tribute from them of 40 submarines. In June, the figures were 18,000 tons only for 17 submarines, and in July, 123,000 tons against 37 German submarines.
And that's not all... The Coastal Defense was carrying out a separate offensive in the main staging areas for submarines coming from and going to the Atlantic. Using the new radar, depth charges tuned to explode at shallow depths, and special searchlights to illuminate detected U-boats at night, they sank 13 more during April and May, taking advantage of a tactical error by Admiral Donitz, who had ordered his submarines to go to their operational zones, on the surface, and there to fight the planes which would attack them. Against the new Allied weapons, they had little chance of success.
It is hardly surprising that, in the face of losses of this magnitude, the morale of the Germans began to weaken. It was a stunning reversal of the tides of battle. It had taken only five weeks since the start of the offensive to force the submarines, at the height of their power and success, to take refuge in less dangerous waters to continue their operations. For nearly three months, after the decisive battles of May, the ocean had been emptied of these submarines. Even when they returned, though never in such numbers, it was evident that their commanders had lost their will to attack.