The Arctic convoys that sailed through the cold, malevolent waters of the Barents Sea ran the gauntlet of German air and sea attack as they struggled to transport vital supplies to Britain's Russian allies. Convoy JW51B sailed in December 1942 with a small escort of five destroyers, and a reserve of two light cruisers shadowed the main convoy at a distance of seventy miles. The convoy was attacked on December 3 by a powerful German force that included the heavy cruiser Admiral Hipper, the pocket battleship Lutzbow, and six destroyers. The ensuing engagement proved the worth of the British Navy. The five British destroyers held off the surprise attack for four hours, until the German ships were driven from the area. The convoy itself sustained no losses.