In 1635 the Dutch Republic concluded an alliance with France with the objective of taking on the Spanish Army of Flanders from two sides, in the hope of breaking the strategic stalemate in the Eighty Years' War and dividing up the
Spanish Netherlands between the two partners in the alliance. The Dutch and French invaded from two sides in June 1635, and joined forces in the valley of the Meuse in July, while the Spanish field army under the Cardinal-Infante fell back to cover behind the well prepared defences of
Brussels instead of risking envelopment by the massive invading Franco-Dutch force, turning the campaign into one of attrition. The invading armies (60,000 strong) captured a few smaller towns before investing
Leuven. But this siege ended in a fiasco because of bad logistics and organization, and because the French army was decimated by the
plague. This failure allowed the Spanish forces to take the initiative and soon the invaders were forced into a headlong retreat. The Cardinal-Infante forced the weakened invading Franco–Dutch armies towards the Dutch border. From there, he made a north-easterly thrust to the Rhine in the direction of
Cleves. Despite desperate efforts, the Dutch and their allies were not able to prevent Spanish forces from taking the towns of
Limbourg,
Gennep,
Diest, and
Goch around the south and east of the Republic. A party of 500 German mercenaries under Lt.-Col. Eyndhouts, roaming on the Cardinal-Infrante's left flank, managed to surprise the unprepared fortress of Schenkenschans that at the time had a garrison of only 120, on the night of 27/
28 July. The garrison were massacred. and the Cardinal-Infante had a large garrison placed in the fortress under the command of Eyndhouts (who died in action in the fort on November 30). ==Siege==