hero of the Count's War (1533–36), the Danish civil war that brought King Christian III to the throne.

In 1523, as the youthful prefect of Gottorp and adviser to Duke Frederick of Holstein, Rantzau persuaded Frederick to accept the offer of the Danish throne from the nobles who had deposed Christian II. At the head of the Duke's army, Rantzau forced the burghers of Copenhagen and Malmö to accept Frederick I as king in 1523. Two years later Rantzau put down a rebellion of the Swedish province of Skåne against the King. In the Count's War, after Frederick's death in 1533, Rantzau led the forces supporting Christian III against the armies of Count Christopher of Oldenburg, which favoured the restoration of Christian II. Rantzau scored decisive victories at the Battle of Öxneberg (June 1535) and in the long siege of Copenhagen (1535–36). After the war Rantzau retired, returning to service for a last victorious campaign against the German republic of Dithmarschen in 1559.