MAC MURCHADA, DIARMAIThigh king of Airgialla, a man who held sway [over the
territory extending] from the Boyne to Derry, and from
Gleann righe [Newry] to Bearamhan in Breifne.” How-
ever, in 1368, even Brian Mór had to yield half of
Airgialla to Niall Mór Ua Néill as éiric(payment;
compensation; legal fine, especially for violation of
honour or manslaughter) for killing Ua Néill’s gal-
loglass constable, and in 1370 Ua Néill killed “very
great numbers of Mac Mahon’s people.” In the late
fifteenth century, Áed Óc (1485–1496) was a powerful
figure. In 1486, he burned 28 townlands belonging to
the English in Airgialla and in 1494 inflicted a sharp
defeat on an English force, killing 60 gentlemen. Having
become blind, he died in 1496. His brother Magnus was
noted for displaying the severed heads of his English
enemies on the palisade around his bawn at Lurgan.
By the sixteenth century there were three main
branches of the Mac Mahon family in Airgialla, the
branches of Monaghan, Dartry, and Farney, all
descended from Ruaidrí who died in 1446. From 1513,
the Monaghan branch of the dynasty monopolized the
chieftaincy. English interference in the Mac Mahon
lordship became very serious as the sixteenth century
progressed. In 1576, Walter Devereux, earl of Essex,
was granted the barony of Farney, and in 1590, the
Mac Mahon chieftain, Hugh Roe, was executed by
Lord Deputy William Fitzwilliam, who divided Air-
gialla up among the chief lords and freeholders. During
the Nine Years’ War, Brian Mac Hugh Óg Mac Mahon
of the Dartry branch, was a prominent leader, of note
for betraying the confederate cause on the eve of the
battle of Kinsale for a bottle of whiskey.
It is important to note that during the medieval
period there was an important and completely separate
Mac Mahon family, lords of Corcu-Baiscinn, in
Thomond, descended from the high king, Muirchert-
ach Ua Briain (d. 1119). In 1404, they are referred to
as Mac Carthy’s “chief maritime officer.” The chieftain,
Tadhg Caech Mac Mahon, lord of west Corc-Baiscinn,
(1595–1602), was prominent during the Nine Years’
War on the Confederate side. He was expelled from
his lordship by the earl of Thomond and fled to Red
Hugh O’Donnell, the lord of Tír Conaill. Tadhg Caech
was shot dead in 1602, it being stated that “There was
no triocha-chead in Ireland of which this Tadhg was
not worthy to have been lord, for [dexterity of] hand,
for bounteousness, for purchase of wine, horses, and
literary works.”
DARREN MCGETTIGAN
References and Further Reading
Duffy, P. J. “The Territorial Organisation of Gaelic Landown-
ership and its Transformation in County Monaghan,
1591–1640.” Irish Geography(1981): 1–26.
MacDuinnshleibhe, Peadar. “The Legal Murder of Aodh Rua
McMahon, 1590.” Clogher Record(1955): 39–52.
O’Donovan, John., ed. and trans. Annala Rioghachta Eireann,
Annals of the Kingdom of Ireland. Dublin, 1856.
Pender, S. “A Tract on MacMahon’s Prerogatives.” Études Celt-
iques(1936): 248–260.
Simms, Katharine. “Gaelic Lordships in Ulster in the Later
Middle Ages.” PhD diss., Trinity College Dublin, 1976.
Smith, Brendan. Colonisation and Conquest in Medieval Ireland,
The English in Louth, 1170–1330. Cambridge, 1999.
See alsoAirgialla; Anglo-Norman; Courcy, John
de; Derry; Military Service; Muirchertach Mac
Carthy; Pale; Ua Briain; Ua Domnaill; Ua Néill;
Ulster, Earldom of; Verdon, deMAC MURCHADA, DIARMAIT
Diarmait Mac Murchada (b. 1110; d. Ferns, 1171), king
of Leinster, was famous as the king who appealed for
military aid to King Henry II of England (1154–1189)
and thereby precipitated the Anglo-Norman invasion.
Mac Murchada is certainly one of the most
maligned historical figures in what is sometimes
termed the “Irish national memory.” There, when he
is remembered at all, it is as a traitor to Ireland, respon-
sible for the oppression of his own race and for post-
poning by eight centuries the emergence of a national
state. It has been with some vigour that Irish historians
have taken on the task of revising this view, and
although a scholarly biography has yet to be published
on Mac Murchada, they have been generally success-
ful. Leaving to one side the problems with teleological
history that links twentieth-century problems with
twelfth-century events, Mac Murchada’s “treasonous”
actions have become comprehensible, even natural,
when he is studied in his own context.Background and Early Career
Wehave an unusually full knowledge of Diarmait Mac
Murchada because we can supplement Gaelic sources
for his career, such as the annals and the Book of
Leinster, with two Anglo-Norman texts documenting
the invasion of Ireland: the Expugnatio Hibernica
(“The Conquest of Ireland”) by Giraldus Cambrensis,
and the metrical history in French known as the Song
of Dermot and the Earl. Nonetheless, his early career
remains relatively obscure. Giraldus included a descrip-
tion of Diarmait in his work on the conquest of Ireland:
Diarmait was tall and well built, a brave and warlike
man among his people, whose voice was hoarse as
a result of constantly having been in the din of battle.
It is not hard to believe that, by the time the first
Anglo-Norman adventurers met Diarmait in the late
1160s, a career spent striving to maintain his position
had hoarsened his voice.