Kurfürst von Brandenburg Johann Sigismund

Johann Sigismund, Kurfürst von Brandenburg (1572-1619), ruled from 1608. By marriage he acquired Prussia (see Ostpreussen) and a hereditary claim on the duchies of Cleves, Jülich, Berg, and Ravenstein, extending Brandenburg-Prussian interest to the west and to both sides of the Rhine. To strengthen his claim he went over from Lutheranism to Calvinism.