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 homage for his kingdom to Henry, and returned to Ireland with promises of aid from the English knighthood.

He was followed in 1168 by Robert FitzStephen, a son of the Constable of Cardigan, with a little band of a hundred and forty knights, sixty men-at-arms, and three or four hundred Welsh archers.
Small as was the number of the adventurers, their horses and arms proved irresistible by the Irish kernes; a sally of the men of Wexford was avenged by the storm of their town; the Ossory clans were defeated with a terrible slaughter, and Dermod, seizing a head from the heap of trophies which his men piled at his feet, tore off in savage triumph its nose and lips with his teeth.

The arrival of fresh forces heralded the coming of Richard of Clare, Earl of Pembroke and Striguil, a ruined baron later known by the nickname of Strongbow, and who in defiance of Henry's prohibition landed near Waterford with a force of fifteen hundred men as Dermod's mercenary.