MAC MURCHADA, DIARMAIT
The homeland of the Meic Murchada dynasty was
Uí Chennselaig, a region in south Leinster with its
center at Ferns in modern County Wexford. Leinster
was traditionally ruled by the Uí Dúnlainge dynasties
of north Leinster. Following the battle of Clontarf in
1014, political instability within the north Leinster
dynasties, and their rivalry with the Meic Gilla Pátraic
of Osraige in south Leinster, enabled a particularly
able king of Uí Chennselaig to seize the kingship of
Leinster in 1042. This was Diarmait mac Máel-na-
mBó (d. 1072). He went on to take the kingship of
Dublin in 1052 and to lay claim, admittedly with oppo-
sition, to the kingship of Ireland. From the death of
Diarmait mac Máel-na-mBó until the coming of the
Anglo-Normans, the kingship of Leinster remained in
the hands of the Uí Chennselaig—an extraordinary feat
for a small and previously unimportant kingdom from
south Leinster.
Diarmait Mac Murchada was a great-grandson of
this king, and he is said to have succeeded his brother
Énna as king of Leinster in 1126. He can, in truth,
have been little more than king of his homeland of
UíChennselaig at first. The intervening Leinster kings
had not retained the power that mac Máel-na-mBó had
attained, and Diarmait—who succeeded aged only
about fifteen—was by no means secure. He was
threatened by dynastic, provincial, and interprovin-
cialenemies. There were certainly others among the
Uí Chennselaig who could have put aside the claim
of a youth like Diarmait, and the northern dynasties
that had lost the Leinster kingship less than a century
before were typically hostile. In terms of external
enemies, the threat to Diarmait is obvious from the
first reference to him in the annals. In 1126, they
report that the king of Connacht, Tairrdelbach Ua
Conchobair, marched into Leinster and deposed “the
son of Mac Murchada”—an inauspicious start to a
career. In order to succeed, then, Diarmait was going
to have to fight.
Diarmait’s early career was spent consolidating his
position in Uí Chennselaig and then asserting his
power over Leinster. Tairrdelbach Ua Conchobhair had
supported the claim to the kingship of Leinster of one
of the Uí Fáeláin, a north-Leinster dynasty based in
modern Kildare. Domestic trouble in Connacht in the
1130s, however, weakened Ua Conchobair’s influence
in Leinster affairs and allowed Diarmait to come to
prominence. He did this spectacularly by perpetrating
a notorious outrage on the abbess of Kildare. Kildare,
with its shrine to St. Brigit, was Leinster’s foremost
monastic institution, and the king of Leinster tradition-
ally held the right to appoint the abbess. In 1132, the
incumbent was an Uí Fáeláin appointee. Diarmait
wished to make way for his own candidate and had
the abbess’s suitability destroyed with a ruthless
expedient. As the annals put it: “The nun herself was
taken prisoner and put into a man’s bed.” His hold on
Leinster was similarly maintained with severity. In
1141, the north-Leinster dynasties rose against Diarmait.
He crushed the rebellion and had seventeen dynasts
from Uí Dúnlainge families and an unspecified number
of lesser nobles killed or blinded. This was an atrocity
even for Diarmait’s contemporaries. A similar action
in 1166 precipitated the fall of the king of Ireland,
Muirchertach Mac Lochlainn. The twelfth century was
not an exclusively violent time. The annals, although
replete with military hostings and depredations, also
report a great number of peace conferences mediated
by the church and reminiscent of the peace movements
on the European continent a century earlier. Diarmait
had established himself as a ruthless ruler. It was a
point that impressed Giraldus Cambrensis, who
remarks, “He [Diarmait] preferred to be feared by all
rather than loved.”Interprovincial Politics and International
Contacts
By 1142, with his rivals in north Leinster devastated,
Diarmait was strong enough to become involved in
interprovincial politics. His policy was expedient: he
cooperated with whomever would best serve his inter-
ests. It is not the case that throughout his career he
harbored a grudge against the kings of Connacht and
sought his political and military allies in the north.
Indeed, in the early 1140s he struck up an alliance with
Tairrdelbach Ua Conchobair based on their mutual
enmity for the Uí Briain of Munster. It is true that
Tairrdelbach’s son, Ruaidrí Ua Conchobair, later
became a bitter enemy of Diarmait and was instrumen-
tal in his downfall in 1166. But this was in the future.
Until Tairrdelbach’s death in 1156, Diarmait’s interests
were best served by not crossing the Connacht king.
Diarmait’s concerns were twofold: to secure control
over Osraige as a buffer between himself and the
UíBriain of Munster, and to exert influence in the
affairs of his northern neighbor Mide. In both these mat-
ters Tairrdelbach Ua Conchobair was to help him.
That Diarmait was not merely ruthless but also
politically adept is shown by his actions in 1151. In
that year, he and Tairrdelbach Ua Conchobair inflicted
a crippling defeat on Tairrdelbach Ua Briain at the
battle of Móin Mór. This victory gave Diarmait enough
power to intervene in Osraige and appoint kings
favourable to him. There was, however, a new power
growing in the north of the country in the form of
Muirchertach Mac Lochlainn, king of Cenél nEógain.
Mac Lochlainn and Diarmait, although they were allies
later, were not initially well disposed toward each