Alfred the Great was an Anglo-Saxon king (871 – 899) of Wessex, an Anglo-Saxon kingdom that existed from 519 to 927 south of the river Thames in England. In the late 9th century, the Vikings had overrun most of the Anglo-Saxon kingdoms that constituted England at the time. Alfred's reign has become regarded as pivotal in the eventual unification of England, after he famously defended Wessex and southern England against the Viking invasions, winning a decisive victory at the Battle of Edington in 878.