Name the King of Wessex from 839 to 858 whose father, King Egbert, defeated Beornwulf of Mercia and who himself led the Battle of Aclea between the West Saxons and the Danish Vikings?
Æthelwulf Æthelwulf (Old English for "Noble Wolf"; died 13 January 858) was King of Wessex from 839 to 858. In 825, his father, King Egbert, defeated King Beornwulf of Mercia, ending a long Mercian dominance over Anglo-Saxon England south of the Humber. Egbert sent Æthelwulf with an army to Kent, where he expelled the Mercian sub-king and was himself appointed sub-king. After 830, Egbert maintained good relations with Mercia, and this was continued by Æthelwulf when he became king in 839, the first son to succeed his father as West Saxon king since 641.
Ælfhere, Ealdorman of Mercia Ælfhere (died in 983) was ealdorman of Mercia. His family, along with those of Æthelstan Half-King and Æthelstan Rota, rose to greatness in the middle third of the 10th century. In the reign of Edward the Martyr, Ælfhere was a leader of the anti-monastic reaction and an ally of Edward's stepmother Queen Dowager Ælfthryth. After the killing of Edward by Ælfthryth's servants in 978, Ælfhere supported the new king, Ælfthryth's son Æthelred the Unready, and was the leading nobleman in the Kingdom of England until his death in 983.