In 1114, Toirdelbhach took advantage of political turmoil in the
Kingdom of Munster, which at the time was ruled by his uncle, Muircherteach Ua Briain,
King of Munster and High King of Ireland, who had previously often supported Toirdelbach as he reigned in Connacht and was the one who backed him to take the Kingship from his brother, had become "sick to the point of a living Skeleton". It was at this point that Diarmuid, brother of Muircherteach, took the Kingship and banished Muircherteach. Tairrdelbach had been scheming against Munster with Muircherteach's enemies, mainly Domnall mac Lochlainn in Ulster and Murchad Ua Máel Sechnaill of the Kingdom of Meath to his east, and they supported Diarmuit's claim to the throne, but Diarmuit soon rose in rebellion against Toirdelbhach. In response, Toirdelbach attacked Munster, ravaging Thomond and expelling Diarmuit. A year later in 1115, Muircherteach Ia Briain regained his strength and led campaigns against his brother to regain the Kingship, with backing from Toirdelbach and other powerful kings, in an attempt to restore order in the province. However, this war would remain a stalemate for several years, and allowed others both within and outside the Kingdom to scheme and form their own plans against Munster. In 1118, Muircherteach and, with backing from Toirdelbach, Ua Máel Sechnaill, and Aéd Ua Ruairc of the Kingdom of Breifne, attacked Tadgh Mac Carthaigh of the
MacCarthy Mór dynasty. But they turned against Muircherteach at
Glanmire in
County Cork, allying with the MacCarthys to remove the High King from power once and for all. At the same time, Toirdelbach's forces attacked
Leinster,
Osraige and
Dublin, which were still held by the Ua Briain's, removing Domnall Ua Briain as governor of Dublin, and forcing the forces of the three kingdoms to join Toirdelbach in his campaigns against Munster. Toirdelbach even went as far as destroying the Ua Briain palace at Kincora,
Killaloe. Meanwhile, in southwest Munster, in modern Counties Cork and Kerry, the Mac Carthaigh (MacCarthys), another royal dynasty of Munster who had been living under the rule of the Ua Briain rebelled. Toirdelbach, eager to further destabilize Munster, backed this revolt. Toirdelbach then resolved the issue he had created by partitioning Munster in 1118. The province was partitioned into the
Kingdoms of Thomond, under the rule of the Ua Briain Dynasty, the
Kingdom of Desmond, under the rule of the
Mac Carthaigh Mór Dynasty, and finally the short-lived
Kingdom of Osraige, under the rule of the Kennedy Dynasty, though the latter kingdom was small in comparison to the other two and were rarely involved in the politics or struggles for the Kingship of Munster. But it was around this point that Muircherteach finally managed to successfully topple his brother Diarmuid from power and retook the Kingship, however, he was now only
King of Thomond, not the whole of Munster. He would die a year later in 1119 at
Lismore. Toirdelbach had successfully divided Munster, and a year later he
annexed the Ua Briain homeland of
County Clare into the
Kingdom of Connacht, leading to the further decline of the Ua Briain dynasty. Toirdelbach had now defeated and partitioned the
Kingdom of Munster, gained the submission of several other kings, and notably ended the Ua Briain's hold of the High Kingship which had lasted since 1002. In 1120 he celebrated the
Oneach Titleann, an event meant to signify one's holding of the High Kingship of Ireland. However, this attracted the attention of Domnall mac Lochlainn of
Ulster. The two kings met at
Athlone where they agreed to a "false peace". Although Mac Lochlainn remained a threat to Toirdelbach he died in 1121, leaving Toirdelbach the most powerful man in Ireland. He immediately subdued unrest in Munster, causing the "people to cry aloud". == Innovation and political strategies ==