[10] The next year Felim marched into Connacht from Tir Eoghain at the head of an army, forcing Toirrdelbach to flee to his erstwhile allies for support.
[11] In 1253 the O'Reilly's, increasingly independent of Connacht's traditional vassal state of Breifne, teamed up with Felim's rival Cathal O Conchobair who had been banished from the kingdom by him in 1250.
[12] In 1255 Aed traveled north to Tir Eoghain and made peace with Connacht exiles who were hiding there out of fear of his father.
They marched together back to Connacht while the descendants of Ruadhrí, rival claimants to the throne, and their Anglo-Norman allies watched but according to the annals dared not attack.
Walter de Burgh 1st earl of Ulster raised an army and marched into Mayo and plundered the region, though he failed to meet up with his O'Reilly allies.
[15] Aed in alliance with Conchobar O'Ruairc king of Breifne raised his own army and met the forces of the O'Reilly's at the Battle of Magh Slecht.
''[15] He also flew into a berserker like rage so that; ''the witnesses of this great battle say that neither the warriors of these bands, nor the champions of the great victory, could gaze at the face of the arch-prince, for there were two broad-eyed, enormous, royal torches flaming and rolling in his head; and every one feared to address him at the time, for he was as far as the voice could reach before the hosts, advancing against the battalions of the Uí-Briuin.
[21] Its also in this year that he traveled, without his father, to Cáel Uisce with Tadhg O'Briain heir to Thomond and recognized Brian Ua Neill as High King of Ireland, handing over the hostages of Connacht to him to signal this.
[24] Soon after Aed and the men of Breifne deposed Domnall, for he had outraged his subjects by killing the chieftain of Tellach Dunchada, and replaced him with Art mac Cathail Ua Ruairc.
[5] He imprisoned Art mac Cathail for an unknown reason and at a meeting arbitrated by Brian Ua Neill, made peace with the former king Domnall and allowed him to resume his kingship.
Felim sent his cattle herds north into Tir Chonaill while Aed traveled to the now unguarded lands of his enemies in Mayo and south Connacht burning towns and killing many.
[41] He had recovered by the next year and was summoned to Athlone by the Anglo-Normans but refusing to attend raised an army and defeated a force of them at the Battle of the Faes.
[43] In 1270 Walter de Burgh and his ally the Justicar of Ireland raised a large army and marched into Roscommon where they encamped for two nights.
Toirrdelbach O Briain was slain single-handedly by the Earl but his army was defeated leaving behind many knights and soldiers dead on the field along with a great bounty of 100 horses.
[45] Uilliam Oc was killed in captivity afterwards in revenge for the slaying of Toirrdelbach and the castles of Ath Angaile, Sliab Luga and Kilcolman were razed with several towns such as Roscommon also burned.