Early Britain was a land of continuous struggle where neighbouring kingdoms competed against each other for power. It was also the time when the early Christian church was growing and strengthening its position as Christian beliefs spread. Into this arena sailed the Vikings in the 8th century when, in AD 793, Lindisfarne, a powerful monastery on the Northumbrian coast, was attacked. This is considered to be the start of the Viking Age in Britain when Vikings from Denmark and Norway raided around the shores of Britain and down through the Irish Sea. .
In AD870 the Vikings mounted an expedition against Alclut, the fortress of the Britons of Strathclyde. Though not the first time the Vikings had raided Strathclyde, this was a particularly devastating attack. It was a two-pronged attack with Olaf the White, the Norse king of Dublin, sailing up the Firth of Clyde and Ivarr the Boneless, the Viking ruler of York, travelling north with his forces. Both were strong and established rulers. Olaf had gained control of Dublin in AD853 and Ivarr had won control of York in AD867. Alclut held out for 4 months until the well on the rock dried up, forcing the defenders to surrender. The Vikings destroyed the fortress. After their victory, however, they did not immediately withdraw, but spent the winter ravaging the lands in and around Strathclyde. This had been a major expedition mounted by the Norsemen. When they returned to Dublin, they took with them fortunes in plundered goods as well as large numbers of Britons, Picts and Northumbrians as slaves. It required 200 ships to transport them back to Ireland. The king of Strathclyde died shortly after and Strathclyde was at the mercy of the surrounding kingdoms. There are no written records of Alclut from this time until the thirteenth century when the kingdom rises again, this time under the Gaelic name of Dun Breatann.