Due to all the Allies' anti-submarine innovations, U-Boat losses are so heavy that by May 1944, North Atlantic operations have virtually ceased. In this period only 25 merchant ships are lost in the North and South Atlantic at a cost of 77 U-boats lost from all causes. At the same time, however, the Allies are not so successful against U-Boats operating in the Bay of Biscay and on passage from Norway to Germany.