The exact dates of his reign are uncertain. According to the Book of Leinster king-list he is given a reign of 27 years which would synchronise to a reign of circa 855 to 882[3] The death of a co-ruler Mugron mac Máele Cothaid is mentioned in 872.[4]
Connacht was subject to the High King of Ireland during this period. In 860 the men of Connacht participated in the expedition of the high king Máel Sechnaill mac Máele Ruanaid (died 862) of Clann Cholmáin against the northern Ui Neill. They halted at Mag Dumai, near Armagh, where their camp was attacked but they beat this attack off and the expedition ended without a clear victor.[5] In 863 the new high king Áed Findliath (died 879) of the Cenél nEógain made an expedition into Connacht to impose his authority.[6]
Conchobar fought as an ally of the high king Áed Findliath against Flann mac Conaing (died 868), King of Brega, and his Viking allies at the Battle of Cell Ua nDaigri in 868. Despite being outnumbered, they won the victory.[7] Conchobar's vassal king, Mannachan, lord of Ui Briuin Na Sinna slew Flann; of which was said:[8]
"Great the triumph for Mannachan, for the hero of fierce valour, to have the head of the son of Conaing in his hand, to exhibit it before the face of the son of Tadhg."
The heir to Connacht, Abán son of Cinaed was killed with fire by Sochlachán son of Diarmait in 867 and in 872 his apparent co-ruler Mugron mac Máele Cothaid died.[11] Conchobar himself died at an old age in 882, according to the annals.[12]
Conchobar had married Ailbe, daughter of the high king Máel Sechnaill mac Máele Ruanaid. Conchobar's sons Áed mac Conchobair (died 888), Tadg mac Conchobair (died 900) and Cathal mac Conchobair (died 925) were all Kings of Connacht. Cathal's descendants were known as the Ua Conchobair (modern O'Connor), the descendants of Conchobar. Another son was named Máel Cluiche (died 913).
Notes
^Francis J. Byrne, Irish Kings and High-Kings, Table 20.
Gearóid Mac Niocaill, ed. (2003). Chronicon Scotorum. Translated by Gearóid Mac Niocaill. Unpublished manuscript made available to UCC – via CELT: The Corpus of Electronic Texts. Edition and translation.