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Mac Murchada, Diarmait [Dermot MacMurrough; called Diarmait na nGall] (c.1110–1171), king of Leinster, was the son of Donnchad Mac Murchada, king of Uí Chennselaig and of Leinster, who was slain in battle in Dublin in 1115, and of Órlaith, who was the daughter of Gille Michil Mac Bráenáin of Uí Máel Rubae and Uchdelb, daughter of Cernachán Ua Gairbith, king of Uí Felmeda. During a long career Mac Murchada sought to extend his authority throughout Leinster and beyond, in the process becoming a notable patron of the reformed religious orders as well as extending his influence in more traditional and brutal ways. To posterity he is best known for his appeal in 1166 to Henry II of England for help in the recovery of his kingdom, from which he had been exiled by his enemies; the act has earned him the dubious distinction of being regarded as the instigator of English involvement in Ireland.

Early years

Mac Murchada was born about 1110, on the evidence of an entry in the king-list in the Book of Leinster. That source attributes to him a forty-six year reign as king of Uí Chennselaig and Leinster, implying that he came to power in 1125–6, following the death of his brother Énna, who died as king of Leinster in 1126; however, the less partisan, though later, Book of Ballymote king-list assigns him a forty-year reign, and this corresponds better with the annalistic evidence, where Diarmait first occurs as king of Leinster in 1132. It is not certain whether he should be identified with ‘the son of Mac Murchada’ who, following the death of Énna, was deposed by Toirdelbach Mór Ua Conchobair (d. 1156), king of Connacht and claimant to the high-kingship, who temporarily intruded his own son, Conchobar, as king of Leinster. But Mac Murchada would appear to have had a dynastic rival for the kingship of Úi Chennselaig in Máelsechlainn mac Diarmata meic Murchada, who was slain in 1133 by north Leinster dynasts led by Augaire Ua Tuathail; the latter was himself killed fighting alongside Diarmait in the following year.

The provincial kingship of Leinster

A distinction may be drawn between Mac Murchada's patrimonial kingdom of Uí Chennselaig in south Leinster, which was centred on Ferns, Wexford, and with which his lineage was associated from the early historic period, and the provincial or over-kingship of Leinster which his great-grandfather, , succeeded in taking by force in 1052. The over-kingship was much less securely held, particularly in the north Leinster region, and in Osraige on the Munster–Leinster border, and was reliant on the exercise of military force, or the latent threat of it. Mac Murchada's first recorded exploit, which may be equated with his crech ríg, or ‘royal prey’ (that is, his first military expedition whereby he inaugurated his kingship), was his attack in 1132 on the important north Leinster church of Kildare and its abbess, Mór. She had been installed there in 1127 by Ua Conchobair, king of Uí Failgi, at the expense of a daughter of Cerball Mac Fáeláin, king of Uí Fáeláin. Another of Cerball's daughters, Sadb, married Mac Murchada, possibly about 1132. The attack on Kildare may therefore be deemed both to have launched Mac Murchada's bid for the provincial kingship, and also to have avenged the insult to his sister-in-law and the Meic Fáeláin, whose support in north Leinster would have been critical to him in establishing his position as king of Leinster.

The expansion of Mac Murchada's sphere of influence is shown by his fighting a battle in 1134 in alliance with the Hiberno-Norse of Dublin against Conchobar Ua Briain, king of Thomond, the Osraige, and the Hiberno-Norse of Waterford. In 1137 he mustered a fleet of 200 ships drawn from Dublin and Wexford and, this time in alliance with Conchobar Ua Briain, besieged Waterford and carried off the hostages of Donnchad Mac Carthaig, king of Desmond, of Déisi, and of Waterford. Conchobar then submitted to Mac Murchada, in the hope that the latter might secure for him the kingship of Desmond. In 1141 seventeen north Leinster dynasts were killed or blinded by Mac Murchada, an event unprecedented not only for the numbers involved, but also for the fact that it was not the consequence of a military campaign, but appears to have been a deliberate rounding up of political opponents. In 1149 he plundered the church site of Duleek, Meath, signalling his interest in expanding into the east Mide area, into which Tigernán Ua Ruairc, king of Bréifne, was also moving. In 1151 he fought alongside Toirdelbach Ua Conchobair at the battle of Móin Mór, Tipperary, at which Toirdelbach Ua Briain, king of Thomond, suffered a crushing defeat.

In 1152 Mac Murchada abducted Tigernán Ua Ruairc's wife, Derbforgaill, from Mide. She was the daughter of Murchad Ua Máelsechlainn, king of Mide, and according to the seventeenth-century translation of the annals of Clonmacnoise, her brother Máelsechlainn had induced her to solicit Mac Murchada's intervention. The Connacht-oriented annals of Tigernach place the abduction in the context of a joint raid with Toirdelbach Ua Conchobair of Connacht, against Tigernán Ua Ruairc, during which Ua Ruairc suffered a defeat and was temporarily deposed. The annals of the four masters record the participation of Muirchertach Mac Lochlainn, king of Cenél nEógain and claimant to the high-kingship, and state that on the same occasion Mide was divided between Murchad Ua Máelsechlainn and his son, Máelsechlainn, who was granted the eastern portion. It is not impossible that Máelsechlainn had offered the kingship of east Mide to Mac Murchada, along with his sister Derbforgaill, as a means of preventing Ua Ruairc's further encroachment upon that area.

Probably shortly after Derbforgaill's return to Mide in 1153, Mac Murchada married Mór, daughter of Muirchertach Ua Tuathail, king of Uí Muiredaig. He may also be presumed to have supported the promotion of her half-brother, Lorcán Ua Tuathail, to the abbacy of Glendalough, even though the latter's hagiographical life reports that he had been mistreated as a boy while held hostage by Mac Murchada. In 1156 Mac Murchada acknowledged the high-kingship of Muirchertach Mac Lochlainn, who confirmed him in the kingship of Leinster and in 1162 he was present at the Synod of Clane, presided over by Gilla Meic Liac, archbishop of Armagh, where the primacy of Armagh was affirmed, and where Lorcán Ua Tuathail most probably was elected to succeed the dying Gréine as archbishop of Dublin. In the same year the annals of Ulster claim that Mac Murchada obtained ‘great power over the Dubliners such as was not obtained for a long time’ (Hennessy and MacCarthy, 2.142–3). He had been assisted by Muirchertach Mac Lochlainn, who led a large army to besiege Dublin in 1162. It must have been with Mac Murchada's consent that the Dublin fleet campaigned for six months in 1165 on the Welsh coast in the service of Henry II.

Expulsion and return

In 1166 the assassination of his ally, the high-king Muirchertach Mac Lochlainn, occasioned a concerted attack on Mac Murchada by his enemies. Ruaidrí Ua Conchobair, king of Connacht, launched a bid for the high-kingship and succeeded in removing the city of Dublin from Diarmait's control, prompting a revolt by the men of Leinster against the latter's authority. Ua Conchobair led an army into Uí Chennselaig, in advance of which Mac Murchada himself burnt Ferns; a second army, led by Tigernán Ua Ruairc, demolished Diarmait's stone house at Ferns and burnt its longphort. Acting as high-king, Ua Conchobair then divided Uí Chennselaig between Diarmait's brother, Murchad (who gave seventeen hostages to Ruaidrí) and Donnchad Mac Gillapátraic, king of Osraige. The Book of Leinster gives 1 August as the date of Mac Murchada's expulsion overseas; he sailed for Bristol and from there travelled on to Aquitaine to secure a personal interview with Henry II, king of England, to seek military aid to help him to recover his kingdom. The request was not unreasonable, considering Henry had hired the Dublin fleet in 1165. Having duly received permission to recruit troops within Henry's dominions, Mac Murchada returned to Bristol, where he was maintained by Robert fitz Harding at the king's expense; it may have been fitz Harding who introduced him to and lord of Striguil, known as Strongbow, whom he sought to recruit. By way of inducement, either then, or later in 1170, Mac Murchada offered Strongbow marriage to his daughter, Aífe, and succession to the kingdom of Leinster after his death. Mac Murchada then moved on to south Wales, where he was entertained by Rhys ap Gruffudd, ruler of Deheubarth, and David fitz Gerald, bishop of St David's. There he recruited Robert fitz Stephen and Maurice Fitzgerald (d. 1176), to whom he offered, according to Gerald of Wales, the town of Wexford and two adjoining cantreds.

In autumn 1167 Mac Murchada returned to Leinster with Cambro-Norman mercenaries and re-established himself without difficulty at Ferns, where he was welcomed by the clergy. Ruaidrí Ua Conchobair responded by marching to Uí Chennselaig and exacting both hostages and 100 ounces of gold, the latter as compensation for the abduction of Ua Ruairc's wife in 1152. In the following year Mac Murchada's son, Énna, was blinded by Donnchad Mac Gillapátraic of Osraige, a deed which underlines the threat which Diarmait's recovery of Uí Chennselaig posed to Donnchad. Then in May 1169 Robert fitz Stephen and Hervey de Montmorency landed at Bannow, where Mac Murchada's forces joined them. Together they moved towards Wexford, whose citizens proffered hostages and submitted to Mac Murchada's authority. They then proceeded to campaign in Osraige. Ruaidrí Ua Conchobair responded by again hosting to Uí Chennselaig and exacting additional hostages. About May 1170 Raymond le Gros Fitzgerald, a member of Strongbow's familia, arrived, following which the men of Waterford suffered a defeat. On 23 August Strongbow himself landed, the city of Waterford was captured on 25 August, and his marriage to Aífe was almost immediately celebrated there. The combined forces of Strongbow and Mac Murchada then marched to Dublin where the city was taken, according to the so-called Song of Dermot and the Earl, on 21 September.

Challenge for the high-kingship and death

Now in a strong enough position to challenge Ruaidrí Ua Conchobair for the high-kingship, Mac Murchada extended his military activities into Mide, where he plundered the church sites of Clonard, Kells, Dulane, and Slane. Ua Conchobair retaliated by executing the hostages whom he held from Mac Murchada; these included the latter's son, Conchobar, his grandson, the son of Domnall Cáemánach, and the son of his foster brother, Murchad Ua Cáellaide, and their deaths show clearly how serious was the challenge which Mac Murchada now posed to Ua Conchobair's high-kingship. However, Mac Murchada died at Ferns about 1 May 1171. By then he had secured hostages from Mide and Airgialla, and had concluded an alliance with Domnall Mór Ua Briain, king of Thomond, to whom he gave his daughter Órlaith in marriage. She was the child of Sadb, who was also the mother of Donnchad, slain by the Osraige at an unknown date. The mother of his son Conchobar, slain in 1170, and of his daughter Aífe, was Mór. The identity of the mother or mothers of his sons Domnall Cáemánach and Énna, and of his daughter Derbforgaill, who married Domnall Mac Gillamocholmóc, king of Uí Dunchada, is unknown. It is probable that only his relationship with Mór was recognized as a canonically valid marriage by churchmen.

Ecclesiastical patronage

Diarmait Mac Murchada was a notable patron of the church reform movement, skilfully combining support for reform with his own political ambitions. His foundation of a Cistercian abbey at Baltinglass, Wicklow, in 1148 (the confirmation of Henry II's son John as lord of Ireland in 1185 refers to Mac Murchada's charter), elicited a letter of confraternity from Bernard of Clairvaux, possibly at the prompting of Archbishop Malachy of Armagh. Baltinglass Abbey served to neutralize a strategic pass connecting north and south Leinster. With the co-operation of Dungal Ua Cáellaide, bishop of Leighlin (who almost certainly owed his episcopal office to Mac Murchada's patronage), he endowed a Benedictine, subsequently Cistercian, abbey at Killenny, for which an original charter, issued by him about 1162–5, is extant, the earliest of an Irish king. Killenny was strategically located near the pass of Gowran, an important route between Osraige and south Leinster.

With the support of Joseph Ua hAéda, bishop of Ferns (who was almost certainly his nominee for the diocese), Mac Murchada introduced an Augustinian community of Arrouaisian filiation at the seventh-century church site of Ferns, which he endowed with the tithes and first fruits of his demesne throughout Uí Chennselaig and to which he granted his capellania (chapel), probably located in his residence at Ferns (which no later than 1166 was built of stone). Although Mac Murchada granted free abbatial election to the community, he reserved to himself and his heirs a right of assent. In the city of Dublin he endowed Holy Trinity Cathedral, the priory of All Hallows (in collaboration with Aéd Ua Cáellaide, bishop of Clogher and head of the Arrouaisian filiation in Ireland), and the Arrouaisian nunnery of St Mary de Hogges, together with its two dependencies at Aghade, Carlow, and Kilculliheen, Waterford. He may also have been responsible for the finely carved Romanesque doorway at Killeshin, Carlow, which shares stylistic features with Baltinglass.

Impact and reputation

The assertion by Gerald of Wales that Diarmait Mac Murchada ‘brought to prominence men of humble rank’ (Giraldus Cambrensis, 40–41) may be substantiated by the rise in the fortunes of his maternal kindred, the Uí Bráenáin, and his foster-kindred, the Uí Cáellaide. He also appears to have settled north Leinster dynasts Ua Briain on assarted land in Dubthír, and Ua Lorcáin in Fothairt in Chairn within Uí Chennselaig. The Leinster ecclesiastic, Aéd Mac Crimthainn, who secured the abbacy of Terryglass in Tipperary in the wake of the battle of Móin Mór in 1151, and whose involvement in the compilation of the Book of Leinster reveals his skills as a propagandist, belonged to the Uí Chremthannáin, who were promoted at the expense of their collaterals, the Uí Mórda of Loígsi. Mac Murchada's personal household included a chancellor (also styled notarius and who probably had custody of his seal), a chaplain, a seneschal, and an interpreter. The latter provided information about him to the author of the so-called Song of Dermot and the Earl, who provides a much more positive portrayal, presenting him as ‘the noble king, who was of so much worth’ (Orpen, 13), than does Gerald of Wales in his Expugnatio Hibernica, where Mac Murchada is portrayed as an oppressive ruler given to outbursts of savagery. The sobriquet Diarmait na nGall, ‘Diarmait of the Foreigners’, although subsequently interpreted as originating from Mac Murchada's recruitment of overseas mercenaries, and used by nationalists as a term of obloquy for his treachery in involving the English in Ireland, more likely derived from his dominance over the Hiberno-Norse of Dublin and Wexford. While contemporary death notices in the Book of Leinster (‘Diarmait … died after the victory of extreme unction and penance’; Book of Leinster, 1.184) and the annals of Inisfallen record his death neutrally, subsequent accounts are noticeably, and increasingly, hostile, reflecting the historiographical evolution of ever more negative assessments of his career.

M. T. Flanagan


W. Stokes, ed., ‘The annals of Tigernach [8 pts]’, Revue Celtique, 16 (1895), 374–419; 17 (1896), 6–33, 119–263, 337–420; 18 (1897), 9–59, 150–97, 267–303, 374–91; pubd sep. (1993) · AFM · D. Murphy, ed., The annals of Clonmacnoise, trans. C. Mageoghagan (1896); facs. edn (1993), 192–3, 196, 199–200, 202, 205–8 · Ann. Ulster · W. M. Hennessy and B. MacCarthy, eds., Annals of Ulster, otherwise, annals of Senat, 4 vols. (1887–1901) · W. M. Hennessy, ed. and trans., The annals of Loch Cé: a chronicle of Irish affairs from AD 1014 to AD 1590, 2 vols., Rolls Series, 54 (1871) · W. M. Hennessy, ed. and trans., Chronicum Scotorum: a chronicle of Irish affairs, Rolls Series, 46 (1866), 332–5 · Sancti Bernardi opera, ed. J. Leclercq and others, 8 (Rome, 1977), 513–14 · C. M. Butler and J. H. Bernard, eds., ‘The charters of the Cistercian abbey of Duiske in the county of Kilkenny’, Proceedings of the Royal Irish Academy, 35C (1918–20), 1–188, esp. 5–7 · R. Butler, ed., Registrum prioratus omnium sanctorum (1845), 50–51 · Dugdale, Monasticon, new edn, 6/2.1141–2 · K. W. Nicholls, ‘The charter of John, lord of Ireland, in favour of the Cistercian abbey of Baltinglass’, Peritia, 4 (1985), 187–206, esp. 191 · C. McNeill, ed., Calendar of Archbishop Alen's register, c.1172–1534 (1950), 293 · G. H. Orpen, ed. and trans., The song of Dermot and the earl (1892) · Giraldus Cambrensis, Expugnatio Hibernica / The conquest of Ireland, ed. and trans. A. B. Scott and F. X. Martin (1978) · M. C. Dobbs, ed. and trans., ‘The Ban-shenchus [pt 2]’, Revue Celtique, 48 (1931), 163–234, esp. 191, 198, 231 · R. I. Best and others, eds., The Book of Leinster, formerly Lebar na Núachongbála, 6 vols. (1954–83), vol. 1, pp. xvii, 184, 186 · R. Atkinson, ed., The book of Ballymote: a collection of pieces (prose and verse) in the Irish language, facs. edn (1887), 55, col. d, ll. 18–26 · M. A. O'Brien, ed., Corpus genealogiarum Hiberniae (Dublin, 1962), 13 · D. Ó Corráin, ‘The education of Diarmait Mac Murchada’, Ériu, 28 (1977), 71–81 · B. Ó Cuiv, ‘Diarmaid na nGall’, Éigse, 16 (1975–6), 136–44 · S. Mac Airt, ed. and trans., The annals of Inisfallen (1951)