Dictionary of National Biography, 1885-1900/O'Brien, Brian Ruadh
O'BRIEN, BRIAN RUADH (d. 1276), king of Thomond, was second son of Conchobhar O'Brien [q. v.] On his father's death in 1267 he was inaugurated chief of the Dal Cais, or king of Thomond, on Magh Adhair; and when Sioda MacNeill MacConmara proclaimed his title, not one of the assembled chiefs of the septs spoke in opposition. He demolished Castle Connell on the Shannon in 1261. He went to war with the English in 1270, and captured the castle of Clare, co. Clare, and in 1272 slew one of the lords justices. In 1275 Sioda MacConmara, who had proclaimed him king, rose against him in the interest of Turlough O'Brien, son of Tadhg of Caoluisce O'Brien, and in alliance with the O'Deas, by whom Turlough had been fostered. They marched to Clonroad in such force that Brian Ruadh, with his sons and household, fled across the Shannon to the cantred of Omullod. There he raised his subordinate chiefs, and, with his son Donogh, entered into alliance with the English of Munster under De Clare. He agreed to give De Clare all the lands between Athsollus and Limerick in return for his alliance. The trysting-place was Limerick, and thence Brian Ruadh, with the men of Cuanach and of Omullod and De Clare, with the Geraldines and the Butlers, marched by night, reaching Clonroad before sunrise, but failed to capture Turlough, as he was absent on a visit to Tadhg Buidh and Ruaidhri MacMathghamhna in Corcovaskin. Brian Ruadh occupied Clonroad, which his father had fortified, and thither came to support him Mathghamhain MacDomhnaill Connachtach O'Brien, with his sons and fighting men, and the O'Gradys and O'Heichirs. Brian attacked the O'Deas and O'Griobhthas, and then marched to Quin, co. Clare, to attack Clancullen and MacConmara, who retired into the woods of Echtghe. De Clare had meantime built the castle, of which the ruins remain, at Bunratty, co. Clare, while Turlough O'Brien collected an army. Brian Ruadh O'Brien and De Clare marched to meet him at Moygressan, but were defeated by Turlough after a long and obstinate battle, and retreated in disorder to Bunratty. Patrick Fitzmaurice, De Clare's brother-in-law, was slain, and De Clare's wife incited her husband against Brian as the cause of this loss. Her father, Fitzmaurice of Kerry, was in the castle, and, by way of satisfaction to them, De Clare, mortified and enraged by his defeat, hanged Brian Ruadh O'Brien there and then (Caithreim). He was succeeded as chief of the Dal Cais and king of Thomond by his nephew, Turlough O'Brien (d. 1306), son of Tadhg of Caoluisce, grandson of Conchobhar O'Brien; the history of Turlough's wars with De Clare is related in the ‘Caithreim Thoirdhealbhaigh’ of Magrath. That work was doubtless composed contemporaneously with the war, as has been shown for the first time by S. H. O'Grady in the edition of the ‘Caithreim’ which has been published by the Cambridge University press.
[Annala Rioghachta Eireann, ed. O'Donovan, vol. iii.; Caithreim Thoirdhealbhaigh of Magrath, ed. S. H. O'Grady, kindly lent by the editor.]