the Danes installed a puppet-king, Ecgberht, to rule in their name and collect taxes for them. Later in the year the Army moved south and invaded the Kingdom of Mercia, capturing the town of Nottingham, where they spent the winter. The Mercian king, Burghred, responded by allying with the West Saxon King Æthelred, and with a combined force they laid siege to the town. The Anglo-Saxons were unable to recapture the city, but a truce was agreed whereby the Danes would withdraw to York. where they remained for over a year, gathering strength for further assaults. The Danes returned to East Anglia in 869, this time intent on conquest. They seized Thetford with the intention of remaining there over the winter, but they were met by an East Anglian army. The East Anglian army was defeated and its commander, King Edmund, was slain. Medieval tradition identifies Edmund as a martyr who refused the Danes' demand to renounce Christ, and was killed for his steadfast Christianity. Ivar and Ubba are identified as the commanders of the Danes, and the killers of Edmund, and it is unknown what part, if any, Halfdan took. Following the conquest of East Anglia Ivar apparently left the Great Heathen Army – his name disappears from English records after 870. However, he is generally considered to be identical to Ímar, a Norse King of Dublin who died in 873. With Ivar in Ireland, Halfdan became the main commander of the Army, and in 870 he led it in an invasion of Wessex. Sometime after Ivar left the Army a great number of Viking warriors arrived from Scandinavia, as part of the Great Summer Army, 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 at 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 its leader. In autumn of 872 the Army returned to Northumbria to quell a revolt against its puppet-regent Ecgberht. However, this explanation for the army's move north has been challenged, and it has been suggested the relocation was a result