The declining number of ships sunk by U-boats did not make the Atlantic benign; submarines remained dangerous whenever they could get into an attack position. Enigma-derived intelligence helped convoys avoid known concentrations, although avoidance by itself did not destroy submarines and German codebreaking complicated the information contest. Centimetric radar could expose a periscope or surfaced boat in most conditions, while fully worked-up escorts were lethal once contact was made. Escort-carrier aircraft and long-range land-based bombers further reduced the safe space in which U-boats could operate. The central operational result was denial: a submarine that could not prosecute its attack could not damage the convoy.
Chapter · 2:56-6:38
Why the U-boat threat receded in 1944-45
Late-war radar, escort carriers, aircraft, and worked-up escorts made it increasingly difficult for U-boats to find and attack convoys.