The hunter-killer and convoy escorts brought the wolfpack era to an end at the close of 1943. Dönitz resorted to sending out single submarines to the far reaches of the oceans in a bid to escape Allied naval power. In November 1943 he sent the last U-boat into the Gulf of Mexico just after the blackout restrictions were lifted. "U-193" achieved one final success. The end of 1943 ended the attempt of the U-boat arm to achieve a strategic victory in the Atlantic. That left only the Arctic convoys to the Soviet Union. On Christmas Eve, this became the sole preserve of the U-boats after the dispatch of "Scharnhorst" at the Battle of the North Cape.