In 685, the Pictish army, commanded by King Bridei III, faced off against an invading force from Northumbria led by King Ecgfrith. This confrontation took place at Dun Nechtain, a site speculated to be near the modern-day location of Dunnichen Hill in Angus, Scotland. The clash stemmed from longstanding tensions between the Picts and Northumbria, as both sought to expand their influence and control over the territories in today's Scotland and northern England. The battle was marked by strategic maneuvers and fierce fighting, ultimately leading to a substantial defeat for the Northumbrians.

King Bridei III's forces, although outnumbered by the Northumbrian army, utilized their knowledge of the terrain and effective battle formations to their advantage. This pivotal victory not only demonstrated the capability and strength of the Pictish warriors but also reaffirmed Bridei's authority and position as a powerful ruler. The aftermath saw Northumbrian troops retreating, significantly curtailing King Ecgfrith's aspirations for dominance over the northern territories. The battle is often regarded as a turning point in the ongoing hostilities between these two kingdoms, illustrating the fierce resistance of the Picts against foreign invasions.

The victory at Dun Nechtain is an essential moment in Scottish history, highlighting the significance of local governance and military strategy in resisting invasion. It strengthened the resolve of the Picts and served as a rallying point for defending their homelands against encroachment. In the aftermath, the Pictish Kingdom consolidated its territories and fostered a greater sense of unity among its clans, setting the stage for continued resistance in the ensuing decades.