Complex sentence: Meanwhile the defeat at Welfesholz had given heart to Henry's enemies; many of his supporters, especially among the bishops, fell away; the excommunication was published at Cologne, and the pope, with the assistance of the Normans, began to make war.
Split into simpler sentences: Meanwhile the defeat at Welfesholz had given heart to Henry's enemies. Many of his supporters, especially among the bishops, fell away, the excommunication was published at Cologne, and the pope, with the assistance of the Normans, began to make war.