O'Donnell ( Ó Domhnaill) became lords of Tír Conaill on the decline of the lordships of O'Maoldoraidh and O'Canannáin in the late 12th and early 13th centuries. In the medieval and early modern period, successive O'Donnell lords extended the traditional boundaries of Tír Conaill, which remained under their rule, independent of the crown, until 1603. The success of the O'Donnell lordship was underpinned by a strong dynasty, despite occasional succession disputes. The heavy military organization of Tír Conaill was also a key factor. O'Donnell's vassal lords and chiefs paid their overlord a
buannacht to maintain his army of mercenaries. By the mid‐14th century, the Scots
gallowglass family of MacSweeny had settled in Tír Conaill. They became key supporters of O'Donnell lordship, and contributed armed soldiers to their O'Donnell overlord, in addition to the required
buannacht.
This level of militarization probably enabled O'Donnell to resist repeated invasions and even limited settlement in the 1250s by Maurice FitzGerald, 2nd baron of Offaly and lord of Sligo, who had received a speculative grant of Tír Conaill from the de
Lacy earls of Ulster. Indeed, in the course of the wars with FitzGerald, Gofraidh O'Donnell (ruled 1247–58) actually extended the southern boundary of Tír Conaill as far as the Drowes estuary, land previously part of Fermanagh.
The Anglo‐Norman threat to Gaelic power in Ulster diminished with the contraction of the colony in the early 14th century. Between 1333 and 1380, a serious succession dispute affected the internal security of Tír Conaill. In 1342 Niall O'Donnell murdered his brother Conor. Opposing factions within the O'Donnell sept subsequently bribed the MacSweenys to back their rival claims to lordship. This effectively undermined the cohesion of Tír Conaill, so that in 1359 the O'Connors of Sligo defeated O'Donnell's army, and briefly ruled the territory until 1362. The succession dispute among the O'Donnells was not resolved until 1380 when Turlough an fhíona, son of Niall, killed his cousin Shane, son of Conor, in battle.
Under Turlough's strong rule, O'Donnell influence was now extended into Connacht, and from the 15th century the northern part of the province paid a permanent tribute to the O'Donnell lords. The decline of the
Maguire lords and of Lower MacWilliam (see
Burke) in the early 16th century facilitated O'Donnell's sustained influence in the region. O'Donnell success also created rivalry with the other Ulster power,
O'Neill, and in the 15th century a dispute arose between the two lordships over the tribute from the Inishowen peninsula, though also concerning control of the district of Ceneal Moen. The resolution of this latter issue established the regional boundaries between the two lordships, later reflected in the country boundaries of Donegal and Tyrone. In 1522 O'Neill unsuccessfully tried to break O'Donnell's regional power, through a confederation of Ulster and Connacht lords.
The comparative stability of the O'Donnell lordship in the early modern period is evident in the almost uninterrupted father‐son succession, from the accession of Hugh Roe in 1461. He was succeeded in 1505 by his son Hugh Dubh, who was in turn succeeded by his son Manus
O'Donnell in 1537. In 1555, however, Manus was deposed by his son Calvagh
O'Donnell, who assumed the lordship in opposition to his brothers and their O'Neill allies. The resultant succession dispute continued until 1566, and weakened O'Donnell lordship. However the cessation of the tribute from north Connacht, as the crown extended its control there, proved a more serious threat to O'Donnell dominion.
The O'Donnells aligned with O'Neill during the
Nine Years War, and the
Ulster plantation permanently removed their land base in the province.
Fiona Fitzsimons
