The rather sudden and decisive turning of the Battle of the Atlantic in favor of the Allies in May 1943 was the result of many factors. The gradual arrival of many more VLR and in October, PB4Y navalized Liberators for anti-submarine missions over the Mid-Atlantic gap ("black pit") and the Bay of Biscay was an important contribution to the Allies' greater success. Liberators were credited in full or in part with sinking 93 U-boats. The B-24 was vital for missions of a radius less than , in both the Atlantic and Pacific theaters where U.S. Navy PB4Y-1s and USAAF SB-24s took a heavy toll of enemy submarines and surface combatants and shipping.