Battle of the Atlantic

The Battle of the Atlantic, 1939 to 1945, was the longest continuous campaign of the Second World War, fought between Allied convoys and German U-boats, surface raiders, and aircraft over the sea lanes that supplied Britain. Wolfpack tactics under Admiral Donitz peaked in early 1943 before escort carriers, very-long-range aircraft, HF/DF, centimetric radar, and broken Enigma traffic turned the tide that May. Allied merchant losses ran into the thousands of ships. Churchill later wrote that it was the one battle whose outcome he most feared.