With the US finally arranging convoys, ship losses to the U-boats quickly dropped, and Dönitz realised his U-boats were better used elsewhere. On July 19, 1942, he ordered the last boats to withdraw from the United States Atlantic coast; by the end of July 1942 he had shifted his attention back to the North Atlantic, where allied aircraft could not provide cover - i.e. the Black Pit. Convoy SC 94 marked the return of the U-boats to the convoys from Canada to Britain. The command centre for the submarines operating in the West, including the Atlantic also changed, moving to a newly constructed command bunker at the Château de Pignerolle just east of Angers on the Loire river. The headquarters was commanded by Hans-Rudolf Rösing.