C. The Jülich-Cleves Succession Question.
The death of John William (March 9, 1609), the mad Duke of Jülich-Cleves, without issue, raised the important question of the succession to his territory, which lay astride the Rhine on the eastern frontier of the United Provinces. It was felt to be essential for the protection of Protestant interests in Germany and the Netherlands that the Duchies should not fall into the hands of a partisan of the house of Habsburg. Duke John William had four sisters, but only the claims of the descendants of the two eldest really counted. Maria Eleanora had married Duke Albert Frederick of Prussia. All her sons, however, had died young, but it was held that her claims had passed to the son of her daughter Anna, who had married John Sigismund, Elector of Brandenburg. This was disputed by the Count Palatine, Philip Lewis of Neuburg, who had married the second sister of the deceased duke, also named Anna. Eventually the Elector and the Count Palatine agreed to occupy the disputed territory jointly, and were known as 'the Possessors'. The Dutch recognized the title of 'the Possessors', but the Emperor Rudolph refused to do so, and with his sanction the Archduke Leopold, Bishop of Passau, at the head of an armed force, made his way into the Duchies and seized the fortress of Jülich. Henry IV of France, who had been meditating an expedition for the overthrow of the Habsburg power, seized the opportunity for planning a great alliance with the Dutch, James I of England, and the Protestant princes of Germany for the expulsion of the Archduke and the recovering of Jülich. His assassination, May 14, 1610, put an end to his ambitious schemes, but though deprived of the help of a great French army, Maurice of Nassau, at the head of a considerable force of Dutch and English troops, entered the Duchies and was joined by the troops of the 'Possessing' princes. On September 1, Jülich surrendered, and Archduke Leopold left the territory. The troubles were not, however, yet over. The 'Possessors', as perhaps might have been expected, quarrelled. John Sigismund of Brandenburg became a Calvinist, Wolfgang William of Neuburg married the sister of the Duke of Bavaria, and announced his conversion to Catholicism. In September, 1614, Maurice of Nassau, with Dutch troops, and Spinola at the head of a Spanish force, both entered the Duchies, and a hostile encounter seemed inevitable. Hostilities were, however, avoided, and by the treaty of Xanten (November 12) the two rivals agreed to a partition of the territory.