 With the Uí Néill kings no great threat during the reigns of Fogartach, Cináed and Flaithbertach, Cathal sought to extend his authority over Leinster.The Cath Almaine claims that the dispute arose because Fergal mac Máele Dúin had been killed in defiance of the truce he had made with Cathal.Cathal was defeated by Áed mac Colggen of the Uí Cheinnselaig, then King of Leinster, in 731, and a second battle in 735 was an even greater defeat