Post-Roman Scotland

In the centuries following the Roman departure from Britain, four distinct groups occupied what is now Scotland. In the east were the Picts, whose territories extended from the River Forth to Shetland. The dominant kingdom was Fortriu, centered around Strathearn and Menteith. The Picts, possibly derived from the Caledonii tribes, were first noted in Roman records at the end of the 3rd century. Their notable king, Bridei mac Maelchon (r. 550–584), had a base at Craig Phadrig near modern Inverness. The Picts converted to Christianity around 563, influenced by missionaries from Iona. King Bridei map Beli (r. 671–693) achieved a significant victory over the Anglo-Saxons at the Battle of Dunnichen in 685, and under Óengus mac Fergusa (r. 729–761), the Picts reached their zenith of power.

To the west were the Gaelic-speaking people of Dál Riata, who had their royal fortress at Dunadd in Argyll and maintained strong ties with Ireland. The kingdom, which reached its height under Áedán mac Gabráin (r. 574–608), faced setbacks after losing to Northumbria at the Battle of Degsastan in 603. Despite periods of subjugation and revival, the kingdom's influence waned before the arrival of the Vikings.

In the south, the Kingdom of Strathclyde, also known as Alt Clut, was a Brythonic realm centered at Dumbarton Rock. It emerged from the Roman-influenced "Hen Ogledd" (Old North) and saw rulers like Coroticus (Ceredig) in the 5th century. The kingdom endured attacks from Picts and Northumbrians, and after its capture by Vikings in 870, its center shifted to Govan.

In the southeast, the Anglo-Saxon kingdom of Bernicia, established by Germanic invaders, was initially ruled by King Ida around 547. His grandson, Æthelfrith, united Bernicia with Deira to form Northumbria around 604. Northumbria's influence expanded under King Oswald (r. 634–642), who promoted Christianity through missionaries from Iona. However, Northumbria's northern expansion was halted by the Picts at the Battle of Nechtansmere in 685.