Owen Roe O'Neill (circa 1590 - 1649), one of the most celebrated of the O'Neill family of Ireland, the subject of the well-known ballad The Lament for Owen Roe, was the son of Art O'Neill, a younger brother of Hugh O'Neill, 2nd Earl of Tyrone (the Great O'Neill). After 40 years abroad, and having served with distinction for many years in the Spanish army, most recently in Flanders, he was immediately recognised on his return to Ireland at Doe Castle in Donegal (end of July 1642) as the leading representative of the O'Neills. Sir Phelim O'Neill resigned the northern command of the Irish rebellion in Owen Roe's favour, and escorted him from Lough Swilly to Charlemont. But jealousy between the kinsmen was complicated by differences between Owen Roe and the Catholic council which met at Kilkenny in October 1642. Owen Roe professed to be acting in the interest of Charles I; but his real aim was the complete independence of Ireland, while the Anglo-Norman Catholicss represented by the council desired to secure religious liberty and an Irish constitution under the crown of England.
Although Owen Roe O'Neill possessed the qualities of a general, the struggle dragged on inconclusively for three or four years. In March 1646 a cessation of hostilities was arranged between Ormonde and the Catholics; and O'Neill, furnished with supplies by the papal nuncio, Rinuccini, turned against the Scottish parliamentary army under Major-General Robert Monro, who had been operating with fluctuating success in Ireland since April 1642. On 5 June 1646 O'Neill utterly routed Monro at Benburb, on the Blackwater; but, being summoned to the south by Rinuccini, he failed to take advantage of the victory, and suffered Monro to remain unmolested at Carrickfergus.
For the next two years confusion reigned supreme among the numerous factions in Ireland, O'Neill supporting the party led by Rinuccini, though continuing to profess loyalty to Ormonde as the king of England's representative. Isolated by the departure of the papal nuncio from Ireland in February 1649, he made overtures for alliance to Ormonde, and afterwards with success to Monck, who had superseded Monro in command of the parliamentarians in the north. O'Neill's chief need was supplies for his forces, and failing to obtain them from Monck he turned once more to Ormonde and the Catholic confederates, with whom he prepared to co-operate more earnestly when Cromwell's arrival in Ireland in August 1649 brought the Catholic party face to face with serious danger. Before, however, anything was accomplished by this combination, Owen Roe died on 6 November 1649.
Original text from Encyclopaedia Britannica 1911