On 25 December 1943 the German battlecruiser Scharnhorst slipped out Altenfjord in Norway to attack Arctic convoy JW55B which was carrying vital war supplies to the Soviet Union. But British naval intelligence knew of the Scharnhorst's mission before she sailed and the vulnerable convoy was protected by a large Royal Naval force including the battleship Duke of York. In effect the Scharnhorst was sailing into a trap. One of the most compelling naval dramas of the Second World War had begun.