As wolves hunt in packs, combing a territory for their food, so Admiral Donitz saw the role of his U-Boat fleet: to hunt in packs, shadowing Allied merchant convoys, picking off their naval escorts, going in for the kill, and disappearing back down into the sea. Keeping Allied sea lanes open was one of the most important objectives of the Second World War, the Battle of the Atlantic. Donitz and his wolf packs almost won it. This is the story of the U-Boat war, from the early victories to ultimate defeat, and includes detailed first-hand accounts of attacks and sinkings by survivors from both sides.