Tairrdelbach Ua Briain was king of Munster (1063-1086) and high king of Ireland (1072-1086). His parents were Tadc, son of Brian Boru, (d. 1023) and Mor, daughter of Gilla Brigte hUf Mael Muaid of Cenel Fhiachach.
Tairrdelbach’s early career was dominated by a feud with his uncle Donnchad mac Briain (d. 1065) who had incited the Eile to kill Tairrdelbach’s father. Tairrdelbach’s marriage to an Eile princess named Gormfhlaith was probably a later peace effort. Tairrdelbach raided his uncle’s lands in upper County Clare in 1053, and attacked Donnchad’s son Murchad in 1055. The feud intensified when Tairrdelbach received support from his foster-father, the Leinster king Diarmait mac Maele na mbo. They attacked Donnchad in 1058, who was forced to burn Limerick to prevent them from capturing it. In 1062, Tairrdelbach and Diarmait returned to County Limerick, destroying Donnchad’s lands and followers. Tairrdelbach was recognized as king of Munster in 1063.
Tairrdelbach could be ruthless. He preempted rebellion in southwest Ireland by a massive raid in 1064. Three years later, Tairrdelbach and Diarmait paid Aed Ua Conchobhair 30 ounces of gold to kill the heir-designate of Teffa. The following year Tairrdelbach, Diarmait, and Domnall Ua Gillai Patraic of Ossory invaded Connacht and provoked a civil war in which Aed and his brother Conchobar were slain. These unsettled conditions sparked a crime wave, and Tairrdelbach had to proclaim legislation in 1068 forbidding the concealment of livestock.
Tairrdelbach always maintained good relations with Diarmait. In 1068, Tairrdelbach received gifts from Diarmait that included his grandfather’s sword and the standard of the English king Edward the Confessor. He returned to Leinster again in 1070, receiving valuables and taking custody of Diarmait’s troublesome nephew Donnchad mac Domnaill. At the same time, he imposed his lordship over Ossory. The death of Diarmait’s sons Gluniairn and Murchad in 1070 led to a power struggle in Leinster. In 1071, Tairrdelbach intervened in the conflict between Diarmait’s grandson Domnall mac Murchada and his nephew Donnchad. Tairrdelbach afterward imposed his lordship over Mide, giving the hostages to Diarmait, and had two bridges built across the Shannon at Thomond Bridge and Killaloe.
When Diarmait was slain in 1072, Tairrdelbach promptly asserted his control over Leinster, Mide, and Dublin. He removed Diarmait’s nephew Donnchad from Dublin and installed Godred son of Olaf, the uncle of his daughter-in-law Mor. The next year, two of his kinsmen joined Godred’s brother Sitric for a raid on the Isle of Man. Family ties were, however, no guarantee of safety. For reasons that are never stated, Tairrdelbach sent Godred into exile in 1075. Domnall mac Murchada briefly seized the kingship, but died before Tairrdelbach returned and installed his son Muirchertach. The five Jews who brought gifts to Tairrdelbach in 1079 may have met him at Dublin.
The final extension of Tairrdelbach’s authority began in 1073. He led a massive assault on eastern Mide after his client king Conchobar was slain by his brother Murchad. He also raided the coast, despoiling the Gailenga and killing Maelmorda Ua Cathusaigh of Brega. Tairrdelbach then went into Connacht and received hostages from Uf Conchobhair and Breifne. The north was a special concern to Tairrdelbach, in part because his cousins Conchobar and Cennetig, sons of Donnchad, had found sanctuary with Cenel nEogain of Tuloch Og. When the king of Ulaid, Donn Sleibe Ua hEochada, was deposed by his kinsman Aed "the furious" in 1078, he submitted to Tairrdelbach at Kincora. Donn Sleibe was reinstated as king by 1080. The unfortunate Aed was in Tairrdelbach’s custody when he drowned at Limerick in 1083. During all this, Tairrdelbach’s son Diarmait raided Wales.
Good relations with the church were maintained by Tairrdelbach. In 1068 he allowed the comarb of Armagh to make a circuit of Munster and to take away a stipend and gifts. Tairrdelbach was among those who petitioned Archbishop Lanfranc of Canterbury to consecrate Gilla Patraic as bishop of Dublin in 1074. Gilla Patraic praised Tairrdelbach’s good government to Lanfranc. In 1082, a bishop from Tairrdelbach’s home of Dal Cais corresponded with Lanfranc. Pope Gregory VII wrote to Tairrdelbach and urged him to support church reform.
Tairrdelbach’s empire began to show signs of strain two years before his death. In 1084, Donn Sleibe began his own empire building when Donnchad Ua Ruairc of Breifne submitted to him at Drogheda. In response, Tairrdelbach led his forces against Ua Ruairc and, with his sons Tadc and Muirchertach, ravaged Breifne. Ua Ruairc moved south—destroying churches in Dal Cais—and east—raiding the lands around Dublin. At this time the men of Mide rose in revolt, and the northern Ui Neill raided Ulaid. Tairrdelbach’s troops put down the rebellion in Meath. On October 19, Tadc and Muirchertach defeated an invading Connacht army at Monecronock; among the slain was Donnchad Ua Ruairc.
In 1085, Tairrdelbach had the first attack of his fatal illness when his hair fell out. He died at the age of 77. Historians have not regarded his career as favorably as that of his illustrious grandsire, but in some respects it was more notable. Tairrdelbach dominated Irish affairs for a longer period, and he died peacefully, with his enemies cowed. Able to adapt to change, Tairrdelbach’s hold on the important Viking commercial centers reflected the increasing financial demands that princes throughout Europe were facing. This sophistication is reflected in the Book of Rights, a treatise on stipends and dues. Tairrdelbach was more than just a political being. While not hesitating to bribe one day and attack the next, as with Aed Ua Conchobhair, he was unfailingly loyal to his foster-father Diarmait, even when he had become the more powerful party. Tairrdelbach’s career shows the problems and opportunities faced by princes throughout late-eleventh-century Europe.
