Between March and May 1943, successful U-boat operations gave way to repeated ambushes and losses. Better detection and attack equipment mattered, along with capable escort ships arriving in useful numbers. River-class frigates were among the ship types entering service during that reversal. They worked within a larger system in which technology, production, and trained crews made the submarine's operating environment steadily harsher.
Chapter · 6:59-7:31
Why 1943 became much more dangerous for U-boats
New technology and the arrival of River-class frigates helped reverse the Atlantic balance during the spring of 1943.