Niall Caille - King of Ailech

King of Ailech

In 827 a conflict within the important church at Armagh led to war. The late Annals of the Four Masters provide a long account of the events. According to this, Cummascach mac Cathail of the Uí Cremthainn, king of the Airgíalla, expelled Niall's confessor Éogan Mainistrech from Armagh, installing his own half-brother, Artrí mac Conchobair, who may have been the son of High King Conchobar mac Donnchada, as abbot of Armagh. The Annals of Ulster describe Artrí as bishop of Armagh in 825 when he imposed the Law of Patrick on Connacht together with Feidlimid mac Crimthainn, the King of Munster, suggesting that he was both acting abbot and as such the spiritual heir of Saint Patrick.

Whatever the exact cause of the conflict, Niall raised an army among the Cenél nEógain and Cenél Conaill and marched on Armagh. He was faced by Cummascach and the Airgíalla, who had been joined by Muiredach mac Eochada, the king of Ulster, and his army. According to the Annals of the Four Masters, the battle at Leth Cam, near modern Kilmore, County Armagh, lasted three days. It was a decisive victory for Niall and northern Uí Néill. Cummascach and his brother Congalach were killed, the Annals of Ulster adding that "many other kings of the Airgialla" also died there. The defeat broke the power of the Airgíalla who were thereafter subject to the northern Uí Néill kings. Artrí was deposed from the abbacy of Armagh and Niall may have installed Éogan Mainistrech there as he is called abbot of Armagh by the Annals of the Ulster in the notice of his death in 834.