The Emperor Rudolph II, however, under the pretext of appointing imperial commissioners to adjudicate upon the rival claims, aroused the suspicions of Brandenburg and Neuburg; and these two came to an agreement to enter into joint possession of the duchies, and were styled "the possessors." The Protestant Union at Heidelberg recognised "the possessors," for it was all-important for the balance of power in Germany that these lands should not pass into the hands of a Catholic ruler of the House of Austria.

For the same reason Brandenburg and Neuburg were recognised by the States-General, who did not wish to see a partisan of Spain established on their borders.

The emperor on his part not only refused to acknowledge "the possessors," but he also sent his cousin Archduke Leopold, Bishop of Passau, to intervene by armed force.

Leopold seized the fortress of Juelich and proceeded to establish himself.
It was an awkward situation, for neither the United Provinces nor the archdukes nor the King of Spain had the smallest desire to make the Juelich succession the cause of a renewal of hostilities, immediately after the conclusion of the truce.

The eagerness of the French king to precipitate hostilities with the Habsburg powers however forced their hands.