The Collas with their army along with a host from Connacht marched to Achaidh Leithdeircc in Fernmagh, southern Ulaid, and fought the Ulaid in seven battles over the course of seven days. The host from Connacht fought the first six battles, and the Collas fought the seventh. It is after this last battle that the king of Ulaid, Fergus Foga, was killed and his army routed. The Collas then pursued the Ulaid east of the "Glen Righe" (the valley of the Newry River in eastern County Armagh), before returning to loot and burn the Ulaid capital, Emain Macha, after which it never again had a king. They then took possession of central Ulaid spanning the modern counties of Armagh, Fermanagh, Londonderry, Monaghan and Tyrone founding the over-kingdom of Airgíalla.