During the Thirty Years' War the elector Philip Christopher von Sotern favoured France, and accepted French protection in 1631.
The theory was that all the imperial business in Germany was supervised by the elector of Mainz, and for Italy by the elector of Cologne.
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.
Nearly the whole of the south-west side of the town is occupied by the palace (1720-1759), formerly the residence of the elector palatine of the Rhine.
The last Count of Promnitz, whose ancestor had purchased both baronies from Frederick of Bohemia in 1556, sold them in 1765 to the elector of Saxony for an annuity of 12,000 thalers (rSoo).