Hostile invasion came first in the form of the Northmen, whose piracy and rapine extended to Ireland as well as to Gaul and Britain. Piracy and rapine we call them now, but to the Northmen they seemed no more criminal than to us seems hunting or fishing. The chief objects of the invader's attack were the monasteries, at once treasuries of Church wealth and hateful to the people of Odin. Ruthlessly the Northman slew and burned. His fleet made him ubiquitous and baffled defence, union for which there was not at first among the tribes. Common danger at last enforced it. A national leader arose in the person of Brian Boru, who was for Ireland the military, though not the political, saviour that Alfred was for England. At the great battle of Clontarf, the host over which the Danish Raven flew was totally overthrown, and Ireland was redeemed from its ravages. The Dane, however, did not wholly depart. Exchanging the rover for the trader, he founded a set of little maritime commonwealths at Dublin, Wexford, Waterford, and Limerick, germs on a small scale and in a rude way of municipal as well as commercial life. But a conqueror, more fell and more tenacious than the Dane, was at hand. In 1169 a little fleet of Welsh vessels ran into the Bay of Bannow. From it landed a band of mail-clad soldiery, men trained to war, with a corps of archers. They were Normans from Wales under the leadership of the Anglo-Norman rover Fitzstephen, and were the precursors of a larger body which presently followed, under Richard Strigul, Earl of Pembroke, from the strength of his arm surnamed Strongbow. Dermot, an Irish chief, expelled for his tyranny, had brought these invaders on his country as the instruments of his revenge. Henry II. had, by giving letters of marque, sanctioned the enterprise, the fruits of which he intended to reap. Early in his reign the king had obtained from Pope Adrian IV., an Englishman by birth, a bull authorizing him to take possession of Ireland, which with other islands the bull declared of right to be an appanage of the Holy See. Here, as in the case of William's invasion of England, the Papacy used Norman conquest as the instrument of its own aggrandizement. The authenticity of the bull is disputed by Irish patriotism, but in vain. No one questions the share of the Papacy in the Norman conquest of England. With the aid of his Norman allies, to whom the Irishman with his naked valour was as the Mexican to the Spaniard, Dermot prevailed and glutted his revenge by plucking from the triumphal pyramid of hostile heads that of his chief enemy and tearing it with his teeth. But in this case, as in that of the alliance of Cortez with the Tlascalans, the ally had conquered for himself. Declining to be dislodged, he proceeded to establish himself and to organize a Norman principality.