ABSTRACT
Muirchertach Mac Lochlainn, son of Niall Mac Lochlainn (1091-1119), prince of Ailech, was a powerful high king of Ireland. The only event of note known of his early life was the killing of his father by the Ua Gairmledaig dynasty of Cenél Móen on 28 December 1119. Thereafter nothing is known of Muirchertach due to the prominence of his grandfather Domnall Mac Lochlainn (d. 1121) and his uncle Conchobar Mac Lochlainn (sl. 1136). Muirchertach first appears after the killing of Conchobar in 1136 by Mathgamain Ua Dubda (sl. 1139), lord of Clann Laithbhertaig, and the men of Mag nItha. Although Muirchertach succeeded his uncle as over king of Northern Ireland, he faced challenges, killing Gillamurra Ua hÓgáin that year. In 1139, the king of Ulaid invaded Muirchertach’s home kingdom of Tír nEógain to Tullaghoge, plundering the churches in the surrounding plains. Smarting still, Muirchertach then killed Mathgamain Ua Dubda and the chief men of his territory. In 1142, he defeated the Uí Dongaile at Feara Droma, but was severely wounded during that battle and weakened politically. For in 1143, Domnall Ua Gairmledaig (sl. 1160) expelled Muirchertach from Tír nEógain and assumed its kingship. During 1145, Muirchertach returned from what is now County Donegal with the Cenél Conaill and defeated Ua Gairmledaig, but failed to depose him. And it took a second expedition to separate Ua Gairmledaig from the kingship.
