Anglo-Saxon Kingdoms or the Heptarchy
Withdrawal of the Roman legions from Britain was followed by invasions of the barbarian peoples (Angles, Saxons, Jutes, Frisians) who occupied about one half of the British Isles by the end of the 6th century. Barbarian invasions resulted in the formation of seven Anglo-Saxon Kingdoms also known as the Heptarchy: Northumbria, Mercia, East Anglia, Essex, Kent, Sussex and Wessex although there were other political units as well which played more important role than it was previously thought. Northumbria, Mercia and Wessex eventually became predominant over other kingdoms but Wessex subdued Mercia and Northumbria during the reign of Egbert of Wessex (802-839). However, the Anglo-Saxon Kingdoms were unable to withstand the Danish invasions which started at the end of the 8th century and resulted in the establishment of Danelaw in today’s northern and eastern England.