Members of the family were also margraves of Brandenburg from 1323 to 1373, and kings of Sweden from 1654 to 1718.
The death without direct heirs of Duke John William in 1609 led to serious complications in which almost all the states of Europe were concerned; however, by the treaty of Xanten in 1614, Cleves passed to the elector of Brandenburg, being afterwards incorporated with the electorate by the great elector, Frederick William.
On the death of this general Descartes quitted the imperial service, and in July 1621 began a peaceful tour through Moravia, the borders of Poland, Pomerania, Brandenburg, Holstein and Friesland, from which he reappeared in February 1622 in Belgium, and betook himself directly to his father's home at Rennes in Brittany.
War broke out between the Protestant states of Sweden, Denmark, Holland and Brandenburg, with whom religion was entirely subordinated to individual aims and interests, and who were far from rising to Cromwell's great conceptions; while the Vaudois were soon subjected to fresh persecutions.
From about 1200 till 1628 it was the seat of a bishopric, which at the latter date became a secular principality, being in 1648 incorporated with Brandenburg.