The Anglo-Saxons were the members of Germanic-speaking groups who migrated to the southern half of the island of Great Britain from nearby northwestern Europe. Anglo-Saxon history thus begins during the period of sub-Roman Britain following the end of Roman control, and traces the establishment of Anglo-Saxon kingdoms in the 5th and 6th centuries (conventionally identified as seven main kingdoms: Northumbria, Mercia, East Anglia, Essex, Kent, Sussex, and Wessex); their Christianisation during the 7th century; the threat of Viking invasions and Danish settlers; the gradual unification of England under the Wessex hegemony during the 9th and 10th centuries; and ending with the Norman conquest of England by William the Conqueror in 1066.