In northern Ireland at this time the head of resistance to the Norsemen was Muirchertach, son of the high-king Niall Glúndubh who fell in the battle of Dublin. A list of his victories is given, a century after his time, by the poet-historian Flann of Monasterboice. Among them is mentioned an expedition by sea against the Norsemen of the Hebrides—it is also mentioned in the genealogies but not in the contemporary annals. The annals on the other hand record that in 939 Muirchertach was captured in Ailech and carried off by the Norsemen to their ships but was immediately ransomed. The event shows that Ailech, one of the great prehistoric stone fortresses, was still occupied in the tenth century by the kings who took their title from it. Especially interesting in Muirchertach's career are his relations with the high king Donnchadh. In the ordinary course of the alternate succession, Muirchertach, as king of Ailech, was the designated successor in the high-kingship to Donnchadh, who was king of Meath. At times he appears prepared to dispute the authority of Donnchadh, at other times he is active in upholding it. His most remarkable action is what is known as his Circuit of Ireland, in 941, briefly noticed in the Annals but described at length in a poem by Cormacán Éces, who accompanied the expedition. With a picked force, said to number 1000, Muirchertach marched through all the principal kingdoms of Ireland, and exacted hostages from each king. In Cashel, he took the king himself, Cellachán, as a hostage. The Dalcassians alone stood off, and after four days marching here and there in their territory, Muirchertach passed on to Connacht without the hostages of Dál gCais.
The fact of this expedition illustrates what I have already said, that, from the sixth to the thirteenth century, there was no military organisation in Ireland. The hostages were brought to Ailech and there hospitably entertained by the king and queen for some weeks, after which Muirchertach, so to speak, regularised his position in the matter by handing over all the hostages to the high king Donnchadh.
Two years later, in 943, Muirchertach fell in battle with the Norsemen near Dundalk. The high king Donnchadh died in the following year, 944. In the ordinary course of the alternate succession, he should have been succeeded by the king of Ailech, but Muirchertach's death left this kingship either disputed or divided, and the high-kingship was assumed by Congalach, king of Bregia, who reigned for twelve years and fell in battle with the Norsemen. This reign of Congalach is the only breach in the alternate monarchy between the years 734 and 1002.
The kingdom of Dál gCais occupied the eastern half of the present county of Clare. Its prominence dates from the time of Lorcán, grandfather of Brian. Being a border state, it was able to form relations of mutual advantage with the border states of Connacht, with Aidne, Ui Maine, and the Delbna. In the wars between Mathgamain and the Limerick Norsemen, the Delbna were his allies. The kings of Aidne and Ui Maine, Connacht states, were allies of Brian, and gave their lives, as he did, on the great day of Clontarf.
The killing of Mathgamain in 976 appears in later writings in a more odious light than it could have appeared to contemporaries. We can recognise that the ancient Eoghanacht dynasty of Cashel, which Mathgamain overthrew, had already lost its prestige and was no longer able to rule and protect Munster. It has always happened in the world's history, and is probably happening to-day, that institutions and established powers appear to contemporary people to be full of vigour and likely to last, whereas to people of a later time it is clear that they resembled the hollow tree awaiting the blast that was to lay it low. To the Eoghanacht princes who compassed the death of Mathgamain, he was the successful usurper who had broken into the ancient right of their kindred and held it by the strong hand.
With regard to Brian, there are some noteworthy things to be said which even enthusiastic eulogists have ignored. Brian had one or two ideas which, in the Ireland of his time, were revolutionary. He had the idea of a more centralised authority than any Irish king in history before him had attempted to create. To this end, he designed holding in permanent garrison a number of fortified places in various parts of Munster. This design is clearly expressed in a poem added in his time, and no doubt under his direction, to the Book of Rights; and the annals show that he endeavoured to give effect to it.
Brian had also definite notions on the subject of what in our time is called sovereign independence. This is one of many matters about which we must be on our guard against thinking the present back into the past—an obvious precaution yet one which many writers on Irish history have neglected. It can be shown, and it would have interested Professor Bury had he known it, that from the earliest Irish chronicle, from the sixth century, down to the eleventh or twelfth century, the dominant idea in Ireland with regard to international relations was this—that as in Ireland there were many little States and over them all, in primacy rather than in operative authority, there was a chief king, the monarch of Ireland, so in the world there were many kingdoms and over all these a chief king whom Irish writers called the king of the world. This idea was adopted from Latin historians, especially from St. Jerome and Orosius. In our earliest histories, the emperor reigning at Constantinople was regarded as king of the world. A metrical list of the kings of the world from Noah's Flood down to the eighth century was written by the poet-historian Flann of Monasterboice, who died in 1056. The prevalence of this idea probably facilitated Henry of Anjou in obtaining the submission of the Irish princes. The annals, in relating Henry's arrival in Ireland in 1171 and his departure in 1172, say nothing about the papal grant, but describe Henry as "the son of the Empress." The same idea lingered in western Europe down to the time of the emperor Charles V, and was the cause of no small anxiety to the mind of Henry VIII, with all his bluffness. Nevertheless, it was very much shaken and confused by the creation of the Western Empire under Charlemagne. That made two kings of the world. If two why not more?
About the year 1000, under Brian, that portion of the Book of Rights which concerns Munster was rewritten, and we have now the new version side by side with the old one. The new poem on the rights of the king of Cashel asserts that Cashel is subject to no king in Ireland but its own. But what about the king of the world? On that point the old idea still holds. This is what the poem says:
Cashel overheadeth every head
Except Patrick and the King of the Stars,
The high-king of the world and the Son of God
To these alone is due its homage.