That transformation had been accomplished without violence or effusion of blood. Until the 8th century it was a source of honour and prosperity for Ireland, for the lustre of her own civilization was enhanced by her renown for piety, and all the neighbouring nations sent their sons in flocks to be instructed in her arts and her virtues.
But the very virtues that made her a country of monks and scholars were doomed before long to become the source of all her misfortunes. When the Scandinavian invasions began to pour over the whole of Europe, Ireland, emasculated by an entirely mystical devotion, was found incapable of sustaining the shock of the Northmen. The disappearance of the Fenian Militia had for a long time left her without a national tie, given up to local rivalries, and broken in pieces, as it were, by the clan system. At the very time that she most urgently needed a powerful central authority to struggle against the black and white strangers from Norway and Denmark, she was found defenceless, and it was not her feeble belt of mountains, opening everywhere on deep bays, that could oppose a serious barrier to them, or guard her plains against their invasions.
Pressed by hunger, the Scandinavians left their country in shoals. They threw themselves on the coasts of Great Britain, France, and Spain, as far as the basin of the Mediterranean. In no place were the people of Europe, already enfeebled by habits of comparative luxury, able to resist those giants of the North, who dauntlessly embarked in their otter-skin boats and dared to go up the Seine even to the very walls of Paris. Ireland was a prey marked out for them. If peradventure the invading party were not numerous enough and were beaten back by numbers, they would come back in thousands the following year and sweep all before them. Vainly did the sons of Erin fight with all the courage of despair; one after the other their chieftains were vanquished, and the foe definitely took up a position on the south-east coast, where he founded the cities of Strangford, Carlingford, and Wexford.
Not content with reducing the Irish to bondage, the victors took a cunning and savage delight in humiliating and degrading them, lodging garnisaries under their roofs, interdicting, under pain of death, the exercise of all liberal arts as well as the carrying of arms, destroying schools, burning books to take possession of the gold boxes that protected their precious binding.
Every ten or twelve years a liberator sprang up in the West or North, and tried to shake off the abhorred yoke. But the rebellion only made it weigh more heavily on the neck of the vanquished; and if it happened that a Brian Boru succeeded, after incredible efforts and heroism, in gathering troops numerous enough to inflict on the stranger a bloody defeat, such a day of glory was invariably followed by the most sinister morrow.
After two centuries of slavery, interrupted by massacres, vain struggles, and impotent efforts, Ireland, once so prosperous, gradually sank in the darkest state of barbarism. The intestine dissensions and the rivalries between clans achieved the work of the Northern Conquerors. In the year 1172 she was ripe for new masters, also of Scandinavian race, who were ready to swoop on her with their Anglo-Saxon bands, after passing, to come to her, through the duchy of Normandy and through Great Britain.
Henry the Second of Anjou, King of England, was resolved to add Ireland to his possessions. All he wanted was a pretext. He found it in the state of practical schism and independence into which the insular Church had fallen. The members of its clergy no longer recognized the Roman discipline, did not observe Lent, and married like those of the Greek rite. Henry the Second solicited and obtained from Pope Adrian II. a bull authorizing him to invade the sister isle, in order to “re-establish therein the rule of the Holy See, stop the progress of vice, bring back respect for law and religion, and secure the payment of St. Peter’s pence.” But in spite of this formal authorization he was too much occupied with Aquitaine to be able to entertain seriously the idea of undertaking the conquest of Ireland, when one of his vassals, Strongbow, cut the knot by landing on the island at the head of a Welsh army, to carve himself a kingdom on the south-east coast.
The way was open; Henry II. threw himself in it in his turn, and established himself in the east of the island, where, strong in the countenance of the clergy secured to him by the Papal bull, he received before long the homage of the principal native chieftains.