In the ninth century the established kingdoms of western Europe found themselves under attack from bands of heathen pirati from Scandinavia. The scourge from the north was seen as divine retribution for the sins of the Christian kings who struggled to mount an effective response.
Initially small groups of ships attacked isolated monasteries, perhaps most famously Lindisfarne in 793. Such raids continued through the first half of the ninth century and, while undoubtedly devastating for their victims, proved only a nuisance for the English kingdoms of Northumbria, Mercia, Wessex and East Anglia, or the powerful Carolingian realms.
In the second half of the ninth century the picture changed, as Viking raiders began larger-scale and longer-term operations. A number of forces began to overwinter at defensible locations on the English and Frankish coasts, launching more systematic attacks and proving a serious threat. In 866 what came to be known as the ‘great army’ came to England and took tribute from the men of East Anglia, in particular acquiring horses. In 867 they moved to York; the two rivals for the throne of Northumbria set aside their differences for long enough to attack the foreigners, only to suffer a catastrophic defeat. In 868 the ‘great army’ wintered in Nottingham, where the combined armies of Mercia and Wessex proved unable to dislodge them. After another year in Northumbria, in 870 the ‘great army’ moved to East Anglia, where King Eadmund was killed attempting to resist them. 871 saw eight battles between Wessex and the ‘great army’, leading to a seven-year truce. The ‘great army’ was only really halted after a decisive defeat at the 878 battle of Edington, after which many of the veterans settled as the new rulers of northern and eastern England – what came to be called the ‘Danelaw’.