Overview
Niall Garbh was incensed at the elevation of his cousin Hugh Roe (Red Hugh) to the chieftainship in 1592, was further alienated when the latter deprived him of his castle of Lifford, and a bitter feud between the two O'Donnells was the result.
While Red Hugh O'Donnell was engaged in the Nine Years' War against the English, Niall Garve exploited the political situation to his own advantage. Niall Garve made terms with the English government, to whom he rendered valuable service both against the O'Neills and against his cousin -enabling an English force to land at Derry under Henry Dowcra. But in 1601 he quarrelled with the lord deputy, who, though willing to establish Niall Garve in the lordship of Tyrconnell, would not permit him to enforce his supremacy over Cahir O'Doherty in Inishowen.
After the departure of Hugh Roe from Ireland in 1602, Niall Garve tried to seize the chieftainship, and was "inaugurated" as the 25th O'Donnell in 1603, but without the full required support of the derbfine (electoral kinship group). This was repudiated by Hugh Roe's surviving family, and especially by his younger brother Rory. To find a solution, Niall Garve, and Hugh Roe's brother Rory went to London in 1603, where the privy council endeavoured to arrange the family quarrel.
As a result, King James I of England granted some lands to Niall Garve, but raised Rory to the peerage as Rory O'Donnell, 1st Earl of Tyrconnell, and also granted him the territorial Lordship of Tyrconnell.
Niall Garve later turned against the Crown, and charged with complicity in Cahir O'Dogherty's rebellion in 1608, he and his son Neachtain were sent to the Tower of London, where they remained till their deaths.
Niall Garve had married his cousin Nuala, sister of Hugh Roe and Rory O'Donnell. When Rory fled with Hugh O'Neill the Earl of Tyrone to Rome in 1607, Nuala, who had deserted her husband when he joined the English against her brother, accompanied him, taking with her her daughter Grania. She was the subject of an Irish poem, of which an English version was written by James Mangan from a prose translation by Eugene O'Curry.
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