Nel 1500 convinse il fratello e il co-duca alla conquista di Dirthmarschen, e un grande esercito fu chiamato non solo dai ducati, ma anche dall'Unione Kalmar, di cui il fratello fu brevemente re. ###>In 1500 he had convinced his brother and co-duke to conquer Dithmarschen, and a great army was called from not only the duchies, but with additions from all of the Kalmar Union for which his brother briefly was king.