After December 1943 when Scharnhorst had been sunk in an attack on an Arctic convoy in the Battle of North Cape by HMS Duke of York, most German surface ships in bases at the Atlantic were blockaded in, or close to, their ports as a fleet in being, for fear of losing them in action and to tie up British naval forces. The largest of these ships, the battleship Tirpitz, was stationed in Norway as a threat to Allied shipping and also as a defence against a potential Allied invasion. When she was sunk, after several attempts, by British bombers in November 1944 (Operation Catechism), several British capital ships could be moved to the Far East.