History

After the death of Conchobar mac Donnchada in 833, Niall became High King. His reign began auspiciously with a victory over Vikings who had raided Derry. This was followed in 835 by an expedition to Leinster. The Annals of Ulster say “Niall led an army to Laigin and he set up a king over the Laigin”. His chosen candidate as king of Leinster was Bran mac Fáeláin of the Uí Dúnlainge. The same year he raided the southern Uí Néill and ravaged the country as far south as modern County Offaly.

The following year, 836, Niall came into conflict with the King of Munster, Feidlimid mac Crimthainn. Feidlimid, who was a churchman as well as a king, abbot of Clonfert and supporter of the austere Céli Dé reformers, attacked Kildare and captured Forindán, the abbot of Armagh. Although this may have been a challenge to Niall, Benjamin Hudson notes that Forindán had replaced Diarmait ua Tigernáin the year before, and that it is not known which of the two rivals Niall supported. In 838 Niall and Feidlimid held a rígdal, a royal conference, either at Cloncurry or at Clonfert. Southern sources such as the Annals of Innisfallen say that Niall acknowledged Feidlimid as High King while northern sources such as the Annals of Ulster simply report the meeting without any further details.

Whatever agreements were made at the rígdal, they did not end the conflict between Feidlimid and Niall. In 840 Feidlimid led an army to the Hill of Tara, where High Kings were inaugurated, and camped there, while Niall again raided into Offaly to undermine support for Feidlimid there. The two did not meet in battle until 841, at Mag nÓchtair, near Cloncurry, where Niall was the victor. A poem in the Annals of Ulster reads: “The crozier of devout Feidlimid/ Was abandoned in the blackthorns;/ Niall, mighty in combat, took it/ By right of victory in battle with swords.” Although Feidlimid ruled for five more years, finally dying in 847, perhaps of disease, he never again campaigned in the north.

While Niall was active in opposing Viking raids in his own lands in the north, he appears not to have campaigned against Viking forces elsewhere. During his reign, the focus of Viking activity moved to the east coast and midlands of Ireland, with permanent settlements established at Lough Neagh and near Dublin. Niall defeated Vikings at Mag nÍtha, in modern County Donegal, in 845. The following year he drowned in the Callan River close to Armagh, from which event his epithet derives. He was buried at Armagh. Niall was followed as High King by Máel Sechnaill mac Máele Ruanaid of Clann Cholmáin.