The background of the battle was the patchwork, fluctuating ethnic and political map of northern Britain. The Irish Gaels of Dal Riata were not in the ascendant and the Picts had been hemmed in at their southern borders by the Northumbrians, who had themselves pinned back the Britons of Strathclyde and ruled British Gododdin for nearly half a century. The ferocious warrior king Ecgfrith of Northumbria had terrorised his neighbours, even to the extent of ravaging the eastern coast of Ireland (possibly pursuing exiled British warriors from Galloway). This latter act earned him the hatred of the Irish monks of Brega, who prayed for the Pictish king who rose up to face him, Brudei son of Bili. The meaning of the surviving verse attributed to a monk of Bangor is extremely allusive, but full of dark hints that the monks cursed the Northumbrian. The words celebrate the 'green swords' of the Picts and praise the Pictish war leader. There is also a strange hint that the English king drank 'black draughts' - a reference possibly to poisoning or a sarcastic reference to the fact that he perished in the murky swap waters of Pictland?
The Northumbrians overran much of southern Pictland in 658 and swiftly crushed a native rebellion in 672. Ecgfrith came north in pursuit of the new Pictish leader Brudei, a native Briton whose father was the king of Strathclyde. The great St Cuthbert and others in Northumbria were against the campaign because supernatural omens predicted disaster. In that year in Northumbria butter and milk was tainted with the colour of blood and throughout Britain there were reports of red coloured rain showers. Even as the war band probably pursued a band of Pictish cavalry north across the Forth on Saturday, 20th May, the monks of Brega were aware of the impending battle, hearing the news on the early medieval grapevine. Their prayers and curses went along with the opposing armies.
The English army may have been lured up Strathearn by their 'fleeing' enemies, then went deeper and deeper into enemy territory, crossing the Tay and travelling east along Strathmore. They may have followed the Pictish men through a cleft in Dunnichen Hill and found themselves trapped in marshy ground by the pool or mere. Behind them a great army poured out of the previously unseen hill fort on the southern slope of the hill. Ecgfrith and his bodyguard were cut to pieces; most of the few English survivors were enslaved. The dreadful slaughter was witnessed far off in England. St Wilfred of York, an old opponent of Ecgfrith, was on his knees in a Sussex church on the afternoon of the battle. Suddenly he had a vision of the king's decapitated corpse falling forwards. Just before the body hit the ground, two demons grasped Ecgfrith's soul and carried it off to hell, moaning dreadfully on its final journey. Did Wilfred smile at the vision of death, along with the monks in Brega?
The psychic panorama of the military disaster was seen in a third place. On the same day, gentle St Cuthbert was indulging in antiquarian examination of the Roman remains in Carlisle. When he suddenly became silent his companions asked him the reason and he told them that he had certain knowledge that the Northumbrian army had been defeated.
The battle certainly led to the liberation of much of Pictland and to the gradual waning of the northern English empire. The Pictish victory of Dunnichen was celebrated by the erection of the famous cross slab at Aberlemno, several miles to the north. It shows helmeted Picts on horse back chasing the enemy cavalry, and native soldiers on foot, armed with swords and shields. One Northumbrian trooper is seen being attacked by a goose, a bird with some of the Celts associated with violent death.
A surprising, delayed 'vision' of the battle, or of its aftermath occurred in the 20th century. Late on the night of 2nd January, 1950, Miss E. F. Smith was walking home to Letham after her car broke down. She felt oddly nervous as she walked along the minor road west of the A932, then she saw a number of strange lights in the distance near Dunnichen Hill. Turning south towards the village, she noticed figure in the field to her right, part of Drummietermont Farm. Each figure carried a flaming red torch in its left hand and they seemed to be searching the ground for something.
Miss Smith then saw shapes on the ground exactly like dead bodies. The figure nearest to her stooped down and examined several of these 'corpses', turning them over and back again, as if looking for recognisable faces. This scene lasted for around ten minutes, with Miss Smith's dog barking throughout. Eventually she simply walked away. She only realised that the whole event was peculiar when she woke up next day and thought about it. Later she gave details of the experience to the Society for Psychical Research. She reported that the searchers wore garb like body stockings, along with tunics and flattened oval helmets. They appeared to be moving around the edge of the vanished mere, the shape of which was later traced by archaeological investigation.
Although this post battle manifestation has not been repeated. some motorists passing through Dunnichen on misty nights have caught sight of fleeting human forms which vanish before their cars hit them.