At the Battle of Edington, an army of the kingdom of Wessex under Alfred the Great defeated the Great Heathen Army led by the Dane Guthrum on a date between 6 and 12 May 878, resulting in the Treaty of Wedmore later the same year. Primary sources locate the battle at "Eðandun". Until a scholarly consensus linked the battle site with the present-day village of Edington in Wiltshire, it was known as the Battle of Ethandun. This name continues to be used.
Events before the battle
The first Viking raid on Anglo-Saxon England is thought to have occurred between 786 and 802 at Portland in the Kingdom of Wessex, when three Norse ships arrived; their men killed King Beorhtric's reeve. At the other end of the country, in the Kingdom of Northumbria, during 793 the holy island of Lindisfarne was raided. After the sacking of Lindisfarne, Viking raids around the coasts were somewhat sporadic until the 830s, when the attacks became more sustained. In 835, "heathen men" ravaged Sheppey. In 836, Ecgberht of Wessex met in battle a force of 35 ships at Carhampton, and in 838 he faced a combined force of Vikings and Cornishmen at Hingston Down in Cornwall.
The raiding continued and with each year became more intense. In 865–866 it escalated further with the arrival of what the Saxons called the Great Heathen Army. The annals do not report the size of the army, but modern estimates suggest between five hundred and a thousand men. It was said to have been under the leadership of the brothers Ivar the Boneless, Ubba, and Halfdan Ragnarsson. What made this army different from those before it was the intent of the leaders. These forces began "a new stage, that of conquest and residence". By 870, the Northmen had conquered the kingdoms of Northumbria and East Anglia, and in 871 they attacked Wessex. Of the nine battles mentioned by the Anglo-Saxon Chronicle during that year, only one was a West Saxon victory. In this year, Alfred succeeded his brother Ethelred, who died after the Battle of Merton.
Mercia had collapsed by 874, and the Army's cohesion went with it. Halfdan went back to Northumbria and fought the Picts and the Strathclyde Welsh to secure his northern kingdom. His army settled there, and he is not mentioned after 876, when "[the Danes] were engaged in ploughing and making a living for themselves". Guthrum, with two other unnamed kings, "departed for Cambridge in East Anglia". He made several attacks on Wessex, starting in 875, and in the last nearly captured Alfred in his winter fortress at Chippenham.
By 878, the Danes held the east and northeast of England; their defeat at the Battle of Ashdown had paused but not halted their advance. Alfred the Great had spent the winter preceding the Battle of Edington in the Somerset marsh of Athelney, protected somewhat by the natural defences of the country. In the spring of 878, he summoned his West Saxon forces and marched to Edington, where he met the Danes, led by Guthrum, in battle.
Alfred's position before the battle
Guthrum and his men had adopted the usual Danish strategy of occupying a fortified town and waiting for a peace "treaty", involving money in return for a promise to leave the kingdom immediately; Alfred shadowed the army, trying to prevent more damage than had already occurred. This started in 875 when Guthrum's army "eluded the West Saxon levies and got into Wareham". They then gave hostages and oaths to leave the country to Alfred, who paid them off. The Danes promptly slipped off to Exeter, even deeper into Alfred's kingdom, where they concluded in the autumn of 877 a "firm peace" with Alfred, under terms that entailed their leaving his kingdom and not returning. This they did, spending the rest of 877 (by the Gregorian calendar) in Gloucester (in the kingdom of Mercia). Alfred spent Christmas at Chippenham (in Wessex), from Gloucester. The Danes attacked Chippenham "in midwinter after Twelfth Night", probably during the night of 6–7 January 878. They captured Chippenham and forced Alfred to retreat "with a small force" into the wilderness. (It is to this period that the story of Alfred burning the cakes belongs.)