Tigernán Ua Ruairc

Tighearnán Mór Ua Ruairc, anglicised as Tiernan O'Rourke ruled the kingdom of Breifne as the 19th king in its Ua Ruairc dynasty, a branch of the Uí Briúin. As one of the provincial kings in Ireland in the twelfth century, he constantly expanded his kingdom through shifting alliances, of which the most long-standing was with Toirdelbach Ua Conchobair King of Connacht and High King of Ireland, and subsequently his son and successor Ruaidhrí Ua Conchobair. He is known for his role in the expulsion of Diarmait Mac Murchada, King of Leinster, from Ireland in 1166. Mac Murchada's subsequent recruitment of Marcher Lords to assist him in the recovery of his Kingdom of Leinster ultimately led to the Anglo-Norman invasion of Ireland.