The fortress of Dumbarton was the stronghold of the kingdom of Alclud, and the centre of British power in northern Britain, for more than two centuries from the mid-seventh century, until the Vikings destroyed the fortress after a four-month siege in 870. The loss of the British power base led to the emergence of the new kingdom of Strathclyde, or Cumbria, with a major centre at Govan. The title "king of the Britons of Srath Clúade" was first used in 872. Dumbarton was later the county town of the county of Dunbartonshire, formerly known as "Dumbartonshire". The name comes from the Scottish Gaelic "Dùn Breatainn" meaning "fort of the Brythons (Britons)", and serves as a reminder that the earliest historical inhabitants of Clydesdale spoke an early form of the Welsh language.