St. Columba, we are told by his biographer, warned the king of Dál Riada to refrain from making war in Ireland on the king of Ireland, and foretold that, if this warning were disregarded, disaster would befall the line of Aedán. Adamnanus goes on to say that this prophecy was fulfilled many years after St. Columba's death. This was written by Adamnanus about fifty years after the event to which he alludes, which was therefore within the memory of many who read his words. Domhnall Breac, king of Dál Riada, he relates, invaded the realm of the king of Ireland. And now, he says, the fulfilment of the warning is visible in the miserable condition to which the kings of Dál Riada are reduced, humiliated by their triumphant enemies.
He refers to the events connected with the battle of Moira in 637. The king of Ireland at the time was Domhnall son of Aedh, that is, son of the king who presided over the Assembly of Druim Ceata. Taking advantage of a quarrel between the Irish monarch and a prince of the north-eastern Picts of Ireland, the Scottish king, as we may call him, put himself at the head of a combination of the north-eastern province and took the field in Ireland. The battle between the two Domhnalls took place at Moira, near Lisburn, and the king of Ireland was victorious. Here we have an instance of the method of contemporary Irish chroniclers. To the chronicler's mind, everybody knew everything that was to be known about this battle and its circumstances, and his record of the event is a mere memorandum in two words. But what were the disastrous results, which, on the testimony of Adamnanus, were notorious when he wrote, i.e. about the year 690? The Irish kingdom in Scotland seems as strong as ever, and is on the eve of a great increase of its power and territory. Once more, as in the instance of the judgment of Druim Ceata, the reference must be particularly to the old Irish kingdom of Dál Riada, which drops into obscurity in the Irish records about that time, possibly becoming tributary either to the neighbouring Picts or to the Northern Ui Néill, whose territory had then extended to the banks of the Bann.
Bede, writing about forty years after Adamnanus wrote, tells about certain things that happened in the lifetime of both, and shows how great an expansion was made by the Irish kingdom of Scotland in the meantime. In the year 684, he relates, his own sovereign, "Egfrid, king of the Northumbrians, sending Beorht, his general, with an army into Ireland, miserably wasted that harmless nation, which had always been most friendly to the English." This statement shows that the power of the Northumbrian Angles extended at the time to the Irish Sea. "In their hostile rage," says Bede, "they spared not even the churches or monasteries." The contemporary Irish chronicler says briefly: "The English devastate the plain of Bregia and many churches in the month of June." Bede continues: "Those islanders, to the utmost of their power repelled force with force, and imploring the assistance of the Divine mercy prayed long and fervently for vengeance; and, though such as curse cannot possess the kingdom of God, it is believed that those who were justly cursed on account of their impiety did soon suffer the penalty of their guilt from the avenging hand of God; for the very next year, that king, rashly leading his army to ravage the province of the Picts, much against the advice of his friends and particularly of Cuthbert of blessed memory who had been lately ordained bishop, the enemy made show as if they fled, and the king was drawn into the straits of inaccessible mountains, and slain, with the greatest part of his forces, on the 20th of May." The Irish chronicle says: "On the 20th of May, on Saturday, the battle of Dún Nechtain was fought, in which Ecgferth, king of the English, was slain together with a great multitude of his soldiers."
Bede, writing forty-six years later, says that from the time of this overthrow the power of the Northumbrian Angles began to decline, and the Picts recovered some of their territory which had been in the possession of the Angles, as well as some which had been taken from them by the Scots. The ancient territory of Northumbria extended to the Firth of Forth. Skene identifies the scene of the battle with a narrow pass in the Sidlaw Hills, north of the Firth of Tay. The territory which the Picts recovered from the Angles must have been between these two firths, corresponding to the modern Fifeshire; and this is apparent from a further statement by Bede. Among the English fugitives from the lost territory, he says, was Bishop Trumwine, who had been made bishop over the English settlers, and who withdrew along with his people who were in the monastery of Abercorn. Abercorn is near the Forth Bridge, about ten miles west of Edinburgh. If the Anglian bishop and his people were forced to abandon this place, it is clear that the recovered Pictish territory reached the Firth of Forth on the opposite side, the north side. But, writing forty-six years after these events, Bede calls the Firth of Forth "the arm of the sea which parts the lands of the Angles and the Scots," not the lands of the Angles and the Picts. Consequently, within those forty-six years, the Scots, who a little earlier appear to have held little or nothing of the mainland outside of Argyleshire, must have extended their power eastward into Fifeshire, occupying that district from which the Picts had expelled the encroaching Angles.
The Britons of south-western Scotland appear to have been hard pressed by this eastward expansion of the Scots and by the Angles of Northumbria, and modern Welsh historians trace an extensive southward migration of Britons through Cumberland and Lancashire into Wales. These migratory Britons, headed by the sons of Cunedda, became thenceforward the dominant people in Wales. They completely displaced the power of the Irish settlers in North Wales, and the descendants of the Irish in South Wales became subordinate to them. About this time, too, many of the displaced Britons took service in Ireland under Irish kings. In 682, a victory was won near Antrim, we are not told by whom, over a combination of Britons and Ulster Picts. In 697, the district of Dundalk was devastated by Britons in alliance with the Ulidians. In 702, Írgalach, king of Bregia, was killed on Ireland's Eye by a party of raiding Britons. In 703, the Ulidians defeated a body of Britons near Newry. In 709, Britons are found fighting in the service of a king of Leinster. In 711 and again in 717, forces of Britons were defeated by Dál Riada. These events all occur within a period of thirty years, about the year 700, and after this time the British incursions are no longer heard of. The movements of the Britons thus chronicled correspond in time with the eastward and perhaps southward expansion of the Scots from Argyle.
Some of the Venerable Bede's pupils must have lived to witness the first appearance of the swarming fleets of heathen Norsemen, towards the close of the eighth century. Within a few decades, the Norsemen held possession of nearly all the islands of Scotland. They also settled on the mainland in Caithness, Argyle, Cunningham and Galloway—at what dates does not appear to be recorded. By thus infesting the entire coast of Scotland, they weakened the power of the Picts in the North and the Angles in the South-east. That there is no sign of any concurrent weakening of the Scots may be taken as proof that the Scots by this time, the early part of the ninth century, had a firm grip of the interior. It may well have been, indeed, that their displacement from Argyle and the islands—their sole possessions in Scotland in the seventh century—may have strengthened the hand of Cinaedh, son of Ailpín (called "Kenneth MacAlpin" in English writings). As arrows in the hand of the mighty, so are the sons of them that have been beaten out. Cinaedh died in 858 after a reign of sixteen years, during which he overthrew the kingdom of the Picts and became ruler of the main part of the country afterwards called Scotland. In recording the death of Cinaedh the Annals of Ulster style him "king of the Picts," meaning that he had brought the Picts under his authority. According to later histories he also obtained the submission of the Britons and Angles of southern Scotland; they certainly ceased to have any considerable power after his time. The Britons held out in their fortress at Dumbarton until 870, when, after a siege of four months, the place was taken by Olaf and Imar, the joint-reigning Norse kings of Dublin. These kings, with a fleet of 200 ships, returned next year to Dublin, "bringing a great spoil of men, Angles and Britons and Picts, in captivity." The Northumbrian kingdom, even south of the Tweed, was crumbling away. In 867, the Norsemen occupied York and defeated the Angles who came against them; and in 876, Halfdene, a Norse commander, parcelled out the remnant of Northumbria among his followers, who settled upon the lands, says the Anglo-Saxon Chronicle, and thenceforth set about ploughing and tilling them. In the same year, 876, Rolf the Ganger, of the line of the Norse earls of the Orkneys, took possession of Normandy.
Here it is well to consider the various fortunes of the Norsemen in different countries. About this period, they became masters of a large part of Russia. In France, they were able to wrest the northern seaboard, between Flanders and Brittany, from the powerful Frankish kings. Over England they effected a gradual conquest, which was only checked, not overcome by the stout resistance of Athelstan and Alfred. In 1013, the year before the battle of Clontarf, all England submitted to Sveinn, king of Denmark. The Normans mastered southern Italy and Sicily. But the Celtic countries, Ireland, Scotland, Wales and Brittany, though particularly exposed to conquest by a people who were then undisputed rulers of the seas on every side, yielded them only a small fraction of their mainland territories. The resistance of Scotland is especially noteworthy. From Norway and Denmark, Scotland was then two days' sail. All the islands and forelands of Scotland were occupied by the Norsemen—the Orkney and Shetland Islands, the Hebrides, Arran and Bute, Caithness, and the peninsulas of Argyle and Galloway; as well as the Isle of Man. But the recently established Scottish monarchy checked all further attempts at conquest, and ultimately recovered the whole country, both mainland and islands.
Another noteworthy fact about this new kingdom was its adoption of a polity quite distinct from that of the older established Britons and Irish in their own countries. In Ireland, the population ranged itself around local places of assembly, according to the traditional habit and convenience of coming together; and the chiefs who presided over these local assemblies took the rank and title of kings. Each of these assemblies was a court of law as well as a court of state. For modern convenience, there are about 150 places in Ireland in which courts of quarter sessions are held. In ancient Ireland, in the ninth century, there were a little more than 100 courts, and the president of each was a king. Everywhere, there was a strong sentiment of local autonomy and the strongest and most ambitious of the superior kings could only maintain a limited degree of centralised power. Probably the Celts came into Ireland in small separate bodies, each colony having its own government, and so no tradition of centralisation ever grew up. In Scotland, on the contrary, from the fifth century onward there was but one kingdom of the Scots, and this one kingdom effected a gradual conquest of the whole country. Thus the Irish system of petty states was not transplanted to Scotland. The highest magnates under the Scottish monarchy bore the title of mór-mhaor, "great steward," which in later times was regarded as the equivalent of "earl." This title is mentioned in the Annals of Ulster under the year 918 and in such a way as to show that it was then a recognised and customary dignity among the oversea Scots. In that year, just 1,000 years ago, Raghnall or "Reginald," founder and king of the Norse colony of Waterford, carried his forces into Britain, finding a small part of Ireland large enough for him. On the banks of the Tyne, in Northumbria, he was met by the army of the Scots—the place indicates how far the power of the Scots at that time extended. An indecisive battle took place, in which, says the annalist, the Scots "lost neither king nor mór-mhaor."
That the conquest of the mainland was followed by a very extensive Gaelic colonisation is evident from the abundance of Gaelic place-names in almost every part of Scotland. They are least numerous in the old Anglian territory of the Lothians and Berwickshire, and from this it is evident that the Anglian population was left for the most part undisturbed. The surname Scott indicates that, among their Anglian neighbours, the great border sept that bore the name was recognised to be of Irish origin. Even in Galloway, a region of Picts and Britons and Norsemen, the Gaelic language became prevalent and the Gaelic people abundant—for in the twelfth century the population of Galloway was known to the Irish and also to the Norsemen as Gall-Ghaedhil, i.e., "Norse-Irish." Though Alan, the Norse earl of Galloway, set himself up as an independent sovereign about the year 1200 and formed an alliance with the English under King John, his language was Irish, for he gave his daughter a name that bespeaks an Irish-speaking household—Dearbhorgaill. The Irish annals call him "king of the Gall-Ghaedhil."