The leadership of the southern branch rested with the rival Clann Cholmáin whose chief, Máel Sechnaill mac Máele Ruanaid, was High King of Ireland.
The Síl nÁedo Sláine had suffered a crushing defeat in 786 at the hands of Donnchad Midi (died 797), the high king from the rival Clann Cholmáin.
Donnchad was deceitfully killed by his rival among the Clann Cholmáin, Flann Sinna in 877 who then became king.
The Annals of Ulster record that Cathal—usually taken to be Cathal mac Finguine, King of Munster—was first of all defeated by Domnall Midi and Clann Cholmáin Máir at Tailtiu, site of the main Uí Néill óenach, and then victorious against Fallomon and Clann Cholmáin Bicc at the Hill of Ward, site of the óenach of Tlachtga, second in importance only to that of Tailtiu.