With the addition of air escort to convoy defense in 1943, U-boat tolls in the North Atlantic diminished and many of the boats were withdrawn during the summer. In the fall, however, Germany began a new U-boat offensive. On 16 September, "St. Croix", then on her first patrol with an offensive striking group in the Bay of Biscay, went to the aid of convoy ONS 18, followed by ON 202, both heavily beset by a wolfpack. The defense of these convoys resulted in a long-running battle with losses to both sides. The convoys lost three escorts and six merchantmen, with two escorts damaged. The wolfpack lost three U-boats.