Every element of improvement or progress which had been introduced into the island disappeared in the long and desperate struggle with the Danes.  The coast-towns which the invaders founded, such as Dublin or Waterford, remained Danish, in blood and manners and at feud with the Celtic tribes around them, though sometimes forced by the fortunes of war to pay tribute and to accept the overlordship of the Irish kings.  It was through these towns however that the intercourse with England which had ceased since the eighth century was to some extent renewed in the eleventh.  Cut off from the Church of the island by national antipathy, the Danish coast-cities applied to the See of Canterbury for the ordination of their bishops, and acknowledged a right of spiritual supervision in Lanfranc and Anselm.  The relations thus formed were drawn closer by a slave-trade between the two countries which the Conqueror and Bishop Wulfstan succeeded for a time in suppressing at Bristol but which appears to have quickly revived.  In the twelfth century Ireland was full of Englishmen who had been kidnapped and sold into slavery in spite of royal prohibitions and the spiritual menaces of the English Church.  The slave-trade afforded a legitimate pretext for war, had a pretext been needed by the ambition of Henry the Second; and within a few months of that king’s coronation John of Salisbury was despatched to obtain the Papal sanction for an invasion of the island.  The enterprise, as it was laid before Pope Hadrian IV., took the colour of a crusade.  The isolation of Ireland from the general body of Christendom, the absence of learning and civilization, the scandalous vices of its people, were alleged as the grounds of Henry’s action.  It was the general belief of the time that all islands fell under the jurisdiction of the Papal See, and it was as a possession of the Roman Church that Henry sought Hadrian’s permission to enter Ireland.  His aim was “to enlarge the bounds of the Church, to restrain the progress of vices, to correct the manners of its people and to plant virtue among them, and to increase the Christian religion.”  He engaged to “subject the people to laws, to extirpate vicious customs, to respect the rights of the native Churches, and to enforce the payment of Peter’s pence” as a recognition of the overlordship of the Roman See.  Hadrian by his bull approved the enterprise, as one prompted by “the ardour of faith and love of religion,” and declared his will that the people of Ireland should receive Henry with all honour, and revere him as their lord.

The Papal bull was produced in a great council of the English baronage, but the opposition was strong enough to force on Henry a temporary abandonment of his designs, and twelve years passed before the scheme was brought to life again by the flight of Dermod, King of Leinster, to Henry’s court.  Dermod had been driven from his dominions in one of the endless civil wars which devastated the island; he now did