Æthelbald was King of Wessex from 855 or 858 to 860. He was the second of five sons of King Æthelwulf. In 850, Æthelbald's elder brother Æthelstan defeated the Vikings in the first recorded sea battle in English history, but he is not recorded afterwards and probably died in the early 850s. The next year Æthelwulf and Æthelbald inflicted another defeat on the Vikings at the Battle of Aclea. In 855, Æthelwulf went on pilgrimage to Rome and appointed Æthelbald King of Wessex, while Æthelberht, the next oldest son, became King of Kent, which had been conquered by Wessex thirty years earlier.

Charles the Bald, also known as Charles II, was a 9th-century king of West Francia (843–877), King of Italy (875–877) and emperor of the Carolingian Empire (875–877). After a series of civil wars during the reign of his father, Louis the Pious, Charles succeeded, by the Treaty of Verdun (843), in acquiring the western third of the empire. He was a grandson of Charlemagne and the youngest son of Louis the Pious by his second wife, Judith.