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.
Even the great fortress of Castra Vetera (Xanten) was starved.
The northern one was the valley of the Meuse and that of the Rhine to a point just south of Bonn: the southern was the rest of the Rhine valley to Switzerland_ Each district was garrisoned at first by four, later by fewer legions, which were disposed at various times in some of the following fortresses: Vetera (Xanten), Novaesium (Neuss), Bonne (Bonn), Moguntiacum (Mainz), Argentorate (Strassburg) and Vindonissa (Windisch in Switzerland).
Otto gained a victory near Xanten, which was followed by the surrender of the fortresses held by his brother's adherents in Saxony, but the rebels, joined by Eberhard of Franconia and Archbishop Frederick of Mainz continued the struggle, and Giselbert of Lorraine transferred his allegiance to Louis IV., king of France.
In the Premonstratensian order, however, founded in I120 by Norbert of Xanten, a new conception of the whole function of monachism was introduced: the duty of the priest-monk is not only to work out his own salvation, but, by preaching and cure of souls, to labour for others.