Finally in 756, having now allied himself with Ongus king of the Picts, he successfully attacked Dumbarton (Alcluith), the chief town of the Britons of Strathclyde.
Part of the shore is skirted by the West Highland railway, opened in 1894, which has stations on the loch at Tarbet and Ardlui, and Balloch is the terminus of the lines from Dumbarton and from Stirling via Buchlyvie.
Its capital was Dumbarton (fortress of the Britons), then known as Alclyde.
In 870 Dumbarton was attacked and destroyed after four months' siege by the Scandinavian king Ivarr, and for some time after this the country was exposed to ravages by the Norsemen.
The next three years was signalized by the reduction one by one of the strong places still held by the English: Linlithgow towards the end of 1310, Dumbarton in October 1311, Perth, by Bruce himself, in January 1312.