Complex sentence: Following the Royalist victory at the Battle of Roundway Down on 13 July 1643, Cooper was one of three commissioners appointed to negotiate the surrender of Dorchester when he negotiated a deal whereby the town agreed to surrender in exchange for being spared plunder and punishment.
Split into simpler sentences: Following the Royalist victory at the Battle of Roundway Down on July 13,1643, Cooper was one of three commissioners appointed to negotiate the surrender of Dorchester. Cooper negotiated a deal whereby Dorchester agreed to surrender in exchange for being spared plunder and punishment.