Background and Early Period
"The Southern Ui Neill" is little more than a convenient designation for the several branches of the Ui Neill that occupied territories stretching across the center of Ireland from north County Dublin to northeastern Connacht.
During the earliest period of recorded history, the fifth and sixth centuries, the dominant branches of the Southern Uf Neill were the descendants of three putative sons of Niall Nofgiallach: Loegaire (Cenel Loeguiri), Coirpre (Cenel Coirpri) and Fiachu (Cenel Fiachach). Cenel Loeguiri had their base near the church of Trim in County Meath and controlled large tracts of land from Lough Erne in the north to Rathlihen, near the Slieve Bloom mountains, in the south. Many historians have concluded that, from the earliest historical period, Cenel Coirpri extended from its base in northeast Connacht to the northern borders of Leinster. It is more probable that the primary Coirpre kingdom was in northeastern Connacht and that the incursion by one branch into northern Tethbae (County Longford), where a separate kingdom was established, occurred as late as the eighth century, while Cenel Coirpri settlement on the Mide-Leinster borders only occurred in the mid-twelfth century, although they had made incursions into Mide before that time. Cenel Fiachach were located in the territory around Uisnech (the traditional center point of Ireland). The earliest list of the kings of Tara, Baile Chuind, includes the names of Loegaire and his son Lugaid, as well as Coirpre and his grandson Tuathal Maelgarb. The history of these early groups is closely associated with the struggle to wrest the northern midlands from the Laigin.
By the mid-sixth century, a branch of Uf Neill claiming descent from Conall Cremthainne mac Neill had assumed a dominant position. Diarmait mac Cerbaill (d. 565) was the first of that line to become over king of the Uf Neill. Two sons of Diarmait, Aed Slaine and Colman, were the ancestors of the two major dynasties that dominated the Southern Uf Neill from the seventh century onward, viz. Sfl nAedo Slaine and Clann Cholmain. Originally these groupings were based in Brega (modern County Meath along with north County Dublin and south County Louth). During the seventh and early eighth centuries, the Sfl nAedo Slaine were in the ascendant, and several of their number became over kings of the Uf Neill during this period. Among these, Ffnsnechta Fledach (d. 695) was perhaps the most notable. He is remembered in later tradition as the king who remitted the Boruma ("the Cattle Tribute") that the Laigin had to pay to the Uf Neill. By the middle of the eighth century, Sfl nAedo Slaine had divided into northern and southern branches. The northern branch, which assumed the name Ciannachta— after the people whose lands they had appropriated— were centered on Knowth; the southern branch was based at Lagore.
The Emergence of Clann Cholmain
Clann Cholmain, which had hitherto been largely subordinate to their Sil nAedo Slaine cousins, began, during the first half of the eighth century, to assume a position of power in the territory to the west of Brega that was to become the kingdom of Mide. From 728 onward, Clann Cholmain excluded Sil nAedo Slaine from the over kingship of the Uf Neill for some two hundred years.
It was during the reign of Donnchad Midi that Clann Cholmain became a dynasty of national importance. Donnchad succeeded in subduing Leinster and the Northern Uf Neill and sought to control Munster as well. Much of his reign was, however, taken up with attempting to subdue the Ciannachta branch of Sil nAedo Slaine. Donnchad’s death, in 797, was followed by a period of limited achievement for Clann Cholmain.
Ninth and Tenth Centuries – The Era of Clann Cholmain Dominance
Mael Sechnaill I mac Maele-Ruanaid advanced the cause of Clann Cholmain further in the mid-ninth century. His obituary in the annals, for the year 862, describes him as riHerenn uile ("king of all Ireland"). The claim is somewhat inflated; while he achieved a significant level of dominance over most of the major dynasties and some notable victories over the Vikings, he faced persistent opposition from the Ciannachta and from Aed Findliath of Cenel nEogain. The reign of Mael Sechnaill’s son, Flann Sinna ("Flann of the Shannon"), enjoyed a remarkably lengthy reign as king of Tara; when he died in 916, he had held the kingship for thirty-seven years. Flann achieved a reasonable measure of military dominance throughout this career, but, not too surprisingly, he faced the growing unrest of his ambitious sons who challenged him on a number of occasions. However, it was as a patron of the church— and, in particular, the monastery of Clonmacnoise— that Flann is best remembered. He built Tempul na Rig at Clonmacnoise in 909, and his patronage of the monastery is commemorated by an inscription on the Cross of the Scriptures.
The emergence of Congalach mac Mael-mithig of Sfl nAedo Slaine as over king of the Uf Neill in 944 represented a break in the two-hundred-year-old convention whereby the kingship alternated between Clann Cholmain and Cenel nEogain (see Uf Neill). The accession of Congalach, who was something of a compromise candidate, was made possible by the complex political circumstances within the Uf Neill dynasty arising from the reemergence of Cenel Conaill as a significant force within the Northern Uf Neill.
Congalach’s reign was relatively unremarkable, and, following his death in 956, the alternating succession between Cenel nEogain and Clann Cholmain was restored.
Mael Sechnaill mac Domnaill (d. 1022) was the last major dynast from the Southern Ui Neill; in fact, his power was already in decline by the turn of the eleventh century, as the balance of power had shifted to Brian Boruma. The eleventh and twelfth centuries witnessed the eclipse of the Ui Neill by the Ui Briain of Dal Cais and the Ui Chonchobhair of Connacht. The power of the Southern Ui Neill was further diminished during this period as a result of the seizure of large tracts of their territories by, among others, the Ui Briuin Breifne.
