Overview
The Three Collas plotted against their uncle, the High King Fíacha Sroiptine. It was prophesied that whoever killed them, his descendants would never rule Ireland. While Fíacha's son Muiredach Tirech was campaigning in Munster with his army, they defeated Fíacha in the Battle of Dubchomar, and Colla Uais took the throne. He ruled for four years, until Muiredach overthrew him, took the throne, and exiled him and his brothers, with three hundred men, to Alba (Scotland). Their mother, Ailech, was the daughter of Udaire, king of Alba, and they took service with their grandfather for three years. After that they returned to Ireland, hoping that Muiredach might kill them, and deprive his descendants of the throne. But Muiredach knew of the prophecy, and despite knowing they had killed his father, took them into his service.
After several years, Muiredach decided the Collas should have territory of their own, and sent them to conquer Ulster. With an army drawn from Connacht, they fought seven battles in a week against the Ulaid at Achaidh Leithdeircc, killing Fergus Foga, king of Ulster, in the seventh. Colla Menn also died in this battle. They burned Emain Macha, the Ulster capital, after which it was abandoned, and seized substantial territories in Ulster, thought to be the origin of the kingdom of Airgíalla.
The chronology of Geoffrey Keating's Foras Feasa ar Éirinn dates Colla Uais' High Kingship to 306-310. The Annals of the Four Masters dates his High Kingship to 322-326, and his destruction of Emain Macha and conquest of Ulster to 331.
However, the chronology of early Irish historical tradition is known to be artificial. One story makes Fiachra Cassán of the Airgíalla, son of Colla Fo Chrí, the foster-father of Cormac mac Airt, who according to the usual chronology was his own great great grandfather, and an alternative tradition dated the fall of Emain Macha to 450. It has been suggested that the Three Collas are doublets of Conall, Endae and Eógan, the three sons of Niall Noígiallach, who also made conquests in Ulster in the 5th century.
Traditionally, the Three Collas were considered to be descended from the same ancestors as Niall Noígiallach. DNA testing of present-day descendants of Niall and the Collas, however, indicates that they were not related.
Read more about this topic: Colla Uais