The North Welsh in Strathclyde, Scots (Irish) in Dal Riada (Argyllshire) and indigenous Picts fight for supremacy in Scotland, being left free to contest their own fate by rivalries among the Anglo-Saxon kingdoms to the south.

The Northumbrians have been gradually extending their territory to the north, their constituent kingdom of Bernicia having in around 638 captured Edinburgh from the Gododdin.

They had established political dominance during the ensuing thirty years over the Kingdoms of Strathclyde and Dál Riata, as well as Pictish Fortriu.

The Picts, under overking Bridei, have warred since 672 against Stratchclyde.

With the settling of the Anglo-Saxon Heptarchy into a pattern of relative order in 685,  the Northumbrian ruler Ecgfrith marshals a huge army, apparently to stop the Picts from raiding to the south.

Ecgrith’s force against the advice of Cuthbert of Lindisfarne advances through Lothian and reaches a site known as Nechtan’s Mere (present Dunnichen in Angus), where he engages a Pictish force of equal strength, led by Bridei.

The Picts defeat the Northumbrians, killing Ecgfrith, and take from the weakened Northumbrian kingdom all its territory beyond the Firth of Forth.