Complex sentence: Chandler: "Marlborough", 153--7 But the problems of coalition warfare proved insurmountable, and with Villars remaining strongly entrenched at Sierck, Marlborough was forced to returned to the Spanish Netherlands.
Split into simpler sentences: Chandler: "Marlborough", 153--7 But the problems of coalition warfare proved insurmountable. With Villars remaining strongly entrenched at Sierck, Marlborough was forced to returned to the Spanish Netherlands.