Brian became lord of
Cairbre Drom Cliabh (
barony of Carbury in what is now
County Sligo. During the late 1170s, King Ruaidhri's power as both King and
High King of Ireland was under severe strain from both
Gaelic-Irish and
Anglo-Norman alike. This encouraged King Flaithbertaigh of
Tyrconnell to mount raids into northern Connacht, an area over which the
Cineál Chonaill had long claimed
jurisdiction. Brian assembled a force and met him in battle
on the Saturday before Whitsuntide, joined by his son, Donogh, his brother
Maghnus Ua Conchobair, and members of leading Connacht
gentry such as Aed
Ó Ceallaigh, Eachmarcach
Ó Muireadhaigh, Giolla Críst
Ó Roduibh, and many others. The
Annals of the Four Masters said of the battle: The list of dead included Brian's son, Donogh; Ó Cellaigh, Ó Muireadhaigh, Ó Roduibh, and members of the O'Mulrenin and Mac Giolla Buidhe clans. ==Descendants==