Dividing up the Spanish Netherlands proved more difficult than foreseen. Olivares had drawn up a strategy for this two-front war that proved very effective. Spain went on the defensive against the French forces that invaded in May 1635 and successfully held them at bay. The Cardinal-Infante brought his full offensive forces to bear on the Dutch, however, in hopes of knocking them out of the war in an early stage, after which France would soon come to terms herself, it was hoped. The Army of Flanders now again numbered 70,000 men, at least at parity with the Dutch forces. Once the force of the double invasion by France and the Republic had been broken, these troops emerged from their fortresses and attacked the recently conquered Dutch areas in a pincer movement. In July 1635 Spanish troops from Geldern captured the strategically essential fortress of the Schenkenschans. This was situated on an island in the Rhine near Cleves and dominated the "back door" into the Dutch heartland along the north bank of the river Rhine. Cleves itself was soon captured by a combined Imperialist-Spanish force and Spanish forces overran the Meierij.