Son of Aed Finliath, Niall is first recorded succeeding his brother Domnall mac Áedo as King of Ailech upon his death in 911. Extending his control to neighboring kingdoms, Niall defeated the Kings of Dál nAraidi and Ulaid at the Battles of Glarryford and Ballymena before his defeat by high-king Flann Sinna mac Maíl Sechnaill of the Clann Cholmáin Uí Néill at the Battle of Crossakiel. Following Flann's death in 916, Niall succeeded him as High King of Ireland. It was during his reign in which he would reestablish the ÓenachTailteann, a traditional gathering of Irish clans. He was married to Gormflaith ingen Flann Sinna. With the support of the clans of Leth Cuinn, the Uí Néill eventually acknowledged his claim to the throne. With a surge of Northmen forces the Uí Ímair launched an invasion in the south of Ireland in the years following 914 which greatly weakened the Eoghanacht of Munster and led to the establishment of a longfort at Waterford. Intent on opposing this, and coming to the assistance of Munster, Niall's forces moved south and fought a large battle against a group of Northmen in the summer of 917, ending inconclusively but with the death of many nobles and tributary kings in his following. The army of the King of Leinster which had been called in to reinforce him however was utterly devastated near St Mullins, leaving the province in a tributary position to the Northmen. Despite his campaigns against the Northmen they continued to settle in large numbers, re-establishing their stronghold in Dublin and various ports on the eastern coast putting pressure on the Midland kingdom of Midhe. In an effort to bring the war to the Northmen, Niall advanced into Leinster, supported by the Uí Néill clans, the Airgíalla and the Ulaid. However, his forces were decimated by the Northmen under Sihtric Cáech as Niall was killed, along with twelve other chieftains, at the Battle of Islandbridge on 14 September 919. Another account in the Anglo-Saxon Chronicle has Sihtric Cáech slaying his brother Niall in 921. Glúndub was succeeded as High King by Donnchad Donn mac Flainn, son of Flann Sinna, and as King of Ailech by his son Muirchertach mac Néill, "the Hector of the Western World".
Family tree
Niall Caille = Gormflaith ingen Donncadha | |____________________________________________________________________________ | | | | Áed Findliath = Gormlaith Rapach = Land ingen Dúngaile = Máel Muire unnamed daughter = Conaing mac Flainn | | | _______________| | Flann | | | | | | | Gormlaith Domnall Eithne Domnall DabaillMáel DubMáel Dúin | = Flann Sinna | | | | Niall Glúndub, d. 919. = Gormflaith ingen Flann Sinna, c.870-948. | | Muirchertach mac Néill, d. 943.
