The five boroughs of Danelaw were established by Alfred the Great through the Peace of Wedmore, agreed with the Danish king Guthrum in 878. When Alfred died he was succeeded by his son, Edward the Elder, although Edward’s cousin, Ethelwald, disputed the succession. Ethelwald gained Danish Viking support and invaded Wessex and Mercia in 903. Edward retaliated by ravaging Mercia, and then withdrew, but part of his army dallied and met the Danes in battle. The Danes prevailed, but Ethelwald was slain. Within a decade Edward went onto the offensive, raiding the kingdom of York and then crushing the Danes at Tettenhall in 910. Breton Vikings raided the Severn Estuary in 914, but were defeated by Edward’s sister Ethelfled’s Mercian army. In the next few years, Edward mopped up Danish resistance south of the York. Victory seemed complete, then in 918 a new threat appeared, when Norse Vikings from Dublin seized Northumbria and York.
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