The recall of German U-Boat Wolfpacks from the central North Atlantic at the end of May 1943 ended the most costly phase of the shipping war for the Allies. Never again would the U-boats inflict dangerously high shipping losses. The naval war remained bitter, however, for the U-boats refused to give up, turning instead to new technology and new tactics. Right to the end of the war, they continued to present a plausible threat, one that caused concern in high Allied circles.
McLean, Douglas M.
"Confronting Technological and Tactical Change: Allied Antisubmarine Warfare in the Last Year of the Battle of the Atlantic,"
Naval War College Review: Vol. 47:
1, Article 7.
Available at: https://digital-commons.usnwc.edu/nwc-review/vol47/iss1/7