Battle of Ellandun

Date	825
Location	near Swindon, Wiltshire
Result	West Saxon victory

Belligerents

Mercia

Wessex

Commanders and leaders

Beornwulf of Mercia

Egbert of Wessex

The Battle of Ellandun or Battle of Wroughton was fought between Egbert of Wessex and Beornwulf of Mercia in September 825. Sir Frank Stenton described it as "one of the most decisive battles of English history". It effectively ended Mercian Supremacy over the southern kingdoms of Anglo-Saxon England and established West Saxon dominance in southern England.

During the 8th century and early 9th centuries, the kings of Mercia exercised a fluctuating hegemony over the kingdoms of south-eastern England, imposing their overlordship and at times exercising direct rule. While Wessex had at times been obliged to recognise the overlordship of Æthelbald of Mercia, it appears to have escaped the dominance of the Mercians thereafter and was certainly not subject to the more intrusive forms of Mercian control imposed on other kingdoms.

Ecgberht's father Ealhmund had been king of Kent in the 780s, which had brought his family into conflict with the ambitions of Offa of Mercia, who sought to impose direct rule on Kent. After his father's death, Ecgberht was driven from England into exile by Offa, with the co-operation of Beorhtric of Wessex and his accession to the throne of Wessex on Beorhtric's death in 802 was immediately followed by a violent clash with Mercia. However, the available sources reveal no further conflict between the two kingdoms before 825.

Beornwulf seized the Mercian throne from Ceolwulf, who had in 821 succeeded on the death of his brother, the long-reigning and powerful Coenwulf. His attack on Wessex two years later may have been part of an effort to consolidate his own authority and reassert that of Mercia after this upheaval.

Beornwulf may also have been seeking to take advantage of Ecgberht's preoccupation with warfare against the Britons of Cornwall. Ecgberht had devastated Cornish territory in 815 and in the autumn of 825 he was again campaigning against the Britons, at Gafulford.

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