Battle of Ellandun
Egbert was in Cornwall with his army when he received word that the Mercians had invaded Wessex. He led his army back into Wessex and met Beornwulf and his army at Ellendun (now Wroughton south of Swindon). In what Frank Stenton called "one of the most decisive battles of Anglo-Saxon history", Egbert defeated Beornwulf. The battle was costly to both sides in loss of life. Henry of Huntingdon said the river ran red with blood. The victory over Mercia shifted the balance of power to Egbert. He was now the most accomplished king in southern England.