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.
House of Wessex The House of Wessex, also known as the House of Cerdic ("Cerdicingas" in Old English), refers to the family that initially ruled a kingdom in southwest England known as Wessex, from the 6th century under Cerdic of Wessex until the unification of the Kingdoms of England by Alfred the Great and his successors (Though Alfred's grandfather Egbert was the one to start consolidating West saxon domination). Alfred and his successors would also be part of this dynasty, which would continue ruling in the main line all the way until Alfred's descendant, Ethelred the Unready, whose reign in the late 10th century and early 11th century saw a brief period of Danish occupation and following his and his son Edmund Ironside's death, kingship by the Danish Cnut the Great and his successors to 1042. The House of Wessex then briefly regained its power for 24 years, but after the deposition of its last scion, Ethelred's great-grandson Edgar Atheling would fade into the annals of history after the death of Edgar Atheling in 1125.