Æthelred of Wessex of Mercia, appealed to him for help against the Vikings. Æthelred and his brother, the future Alfred the Great, led a West Saxon army to Nottingham, but there was no decisive battle, and Burgred bought off the Vikings. In 874 the Vikings defeated Burgred and drove him into exile. In 870 the Vikings turned their attention to Wessex, and on 4 January 871 at the Battle of Reading, Æthelred suffered a heavy defeat. Although he was able to re-form his army in time to win a victory at the Battle of Ashdown, he suffered further defeats on 22 January at
Halfdan Ragnarsson led by Bagsecg, bolstering the ranks of Halfdan's army. According to the "Anglo-Saxon Chronicle", the Danes battled the West Saxons nine times, including the Battle of Ashdown on 8 January 871. However, the West Saxons could not be defeated, and Halfdan accepted a truce from Alfred, newly crowned king of Wessex. The Army retreated to the captured town of London and stayed there over the winter of 871/872. Coins minted in London during this period bear the name Halfdan, identifying him as the leader of the army. In autumn of 872 the Army returned to Northumbria to quell a revolt