By the 8th century the four main Anglo-Saxon kingdoms were Mercia, Wessex, East Anglia and Northumbria. But in the 9th century sporadic Viking raiders began to arrive from the north and the Anglo-Saxon kingdoms faced a huge upheaval. After a period of In 865 the Danes mounted a full-scale invasion, arriving in England with the “Great Heathen Army”. Within ten years much of Anglo-Saxon England had fallen to the invaders: Northumbria 867; East Anglia; most of Mercia 874–77. Only Wessex was able to withstand the onslaught and, following King Alfred’s defeat of the Vikings in 878, a peace treaty was signed at Wedmore, in which the Viking leader Gudrun agreed to withdraw from Wessex and become a Christian. The boundaries of Wessex were re-defined to include western Mercia and the south; the area that would henceforth be under Viking control was known as the “Danelaw”. All over England “burhs”, defensive structures that were often based on old Roman cities, reflected the fact that the country was effectively on a war footing. The Five Boroughs of the Danelaw were the five main towns of Danish Mercia: Derby, Leicester, Lincoln, Nottingham, Stamford. Each was a Danish jarldom, ruled by a chieftain, which controlled the land around a fortified burh that represented the centre of political power. Initially the Mercian boroughs were probably subject to their overlords in the Kingdom of Jorvik (York). Further south were the burhs of Bedford, Cambridge, Huntingdon, Northampton and Tempsford, which were loosely allied to the Five Boroughs and to the King of East Anglia.
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