At no former period, - not even at the height of the tyranny of Turgesius, - was a capable Prince more needed in Erin. The new generation of Northmen were again upon all the estuaries and inland waters of the Island. In the years 923-4 and 5, their light armed vessels swarmed on Lough Erne, Lough Ree, and other lakes, spreading flame and terror on every side. Clonmacnoise and Kildare, slowly recovering from former pillage, were again left empty and in ruins. Murkertach, the base of whose early operations was his own patrimony in Ulster, attacked near Newry a Northern division under the command of the son of Godfrey (A.D. 926), and left 800 dead on the field. The escape of the remnant was only secured by Godfrey marching rapidly to their relief and covering the retreat. His son lay with the dead. In the years 933, at Slieve Behma, in his own Province, Murkertach won a third victory; and in 936, taking political advantage of the result of the great English battle of Brunanburgh, which had so seriously diminished the Danish strength, the Roydamna, in company with the King, assaulted Dublin, expelled its garrison, levelled its fortress, and left the dwellings of the Northmen in ashes. From Dublin they proceeded southward, through Leinster and Munster, and after taking hostages of every tribe, Donogh returned to his Methian home and Murkertach to Aileach. While resting in his own fort (A.D. 939), he was surprised by a party of Danes, and carried off to their ships, but, says the old translator of the Annals of Clonmacnoise, "he made a good escape from them, as it was God's will." The following season he redoubled his efforts against the enemy. Attacking them on their own element, he ravaged their settlements on the Scottish coasts and among the isles of Insi-Gall (the Hebrides), returned laden with spoils, and hailed with acclamations as the liberator of his people.
Of the same age with Murkertach, the reigning Prince at Cashel was Kellachan, one of the heroes of the latter Bards and Story-tellers of the South. The romantic tales of his capture by the Danes, and captivity in their fleet at Dundalk, of the love which Sitrick's wife bore him, and of his gallant rescue by the Dalcassians and Eugenians, have no historical sanction. He was often both at war and at peace with the foreigners of Cork and Limerick, and did not hesitate more than once to employ their arms for the maintenance of his own supremacy; but his only authentic captivity was, as a hostage, in the hands of Murkertach. While the latter was absent, on his expedition to Insi-Gall, Kellachan fell upon the Deisi and Ossorians, and inflicted severe chastisement upon them-alleging, as his provocation, that they had given hostages to Murkertach, and acknowledged him as Roydamna of all Erin, in contempt of the co-equal rights of Cashel. When Murkertach returned from his Scotch expedition, and heard what had occurred, and on what pretext Kellachan had acted, he assembled at Aileach all the branches of the Northern Hy-Nial, for whom this was cause, indeed. Out of these he selected 1000 chosen men, whom he provided, among other equipments, with those "leathern coats," which lent a soubriquet to his name; and with these "ten hundred heroes," he set out - strong in his popularity and his alliances - to make a circuit of the entire island (A.D. 940). He departed from Aileach, says his Bard, whose Itinerary we have, "keeping his left hand to the sea;" Dublin, once more rebuilt, acknowledged his title, and Sitrick, one of its lords, went with him as hostage for Earl Blacair and his countrymen; Leinster surrendered him Lorcan, its King; Kellachan, of Cashel, overawed by his superior fortune, advised his own people not to resist by force, and consented to become himself the hostage for all Munster. In Connaught, Conor, (from whom the O'Conors take their family name), son of the Prince, came voluntarily to his camp, and was received with open arms. Kellachan alone was submitted to the indignity of wearing a fetter. With these distinguished hostages, Murkertach and his leather-cloaked "ten hundred" returned to Aileach, where, for five months, they spent a season of unbounded rejoicing. In the following year, the Roydamna transferred the hostages to King Donogh, as his suzerain, thus setting the highest example of obedience from the highest place. He might now look abroad over all the tribes of Erin, and feel himself without a rival among his countrymen. He stood at the very summit of his good fortune, when the Danes of Dublin, reinforced from abroad, after his "Circuit," renewed their old plundering practices. They marched north, at the close of winter, under Earl Blacair, their destination evidently being Armagh. Murkertach, with some troops hastily collected, disputed their passage at the ford of Ardee. An engagement ensued on Saturday, the 4th of March, 943, in which the noble Roydamna fell. King Donogh, to whose reign his vigorous spirit has given its main historical importance, survived him but a twelvemonth; the Monarch died in the bed of repose; his destined successor in the thick of battle.