But the conquest of Ireland was different, and complete. Ireland, lying out in the western sea, had escaped the incursions of the Saxons, the Danes, and the Normans that had fallen upon England. Sea-rovers had constantly harried her coasts, as they harried every coast within reach of their sails and oars, and made some settlements there; but the island as a whole had not been overrun by any invaders since the coming of the Celts. In Ireland, thus cut off from the rest of the world, the Church went its own way in less dependence on the Pope at Rome than, any other in all the Western world. In the Eastern Empire and in all the vast territories of the Slavs the Patriarch at Constantinople was looked up to as the head of what came, in later days, to be known as the Greek Church. It conducted its services rather differently from the Roman Church, {152} and there were some differences in the doctrines of the two. The Church of Constantinople was too strong for the Church of Rome to prevail against it in the East, but Rome claimed universal spiritual authority in the West. The Pope, moreover, by virtue of a before-mentioned deed signed by Constantine, and called the Donation, or gift, of Constantine, was reputed to have authority over all islands. It did not matter that this famous Donation, or the deed by which it was supposed to be instituted, was strongly suspected to be a forgery, nor did it matter that even if it really were drawn up by Constantine and signed by him, his right to give away authority over "islands" was not quite clear, although he were the emperor of the world. No matter. This gift of "islands," though the document, or deed, was doubtful, was destined to play an important part in the world's story when that story began to be concerned with the discoveries of new continents and islands. For the moment it served to authorise the Pope to give our Henry II. a mandate to conquer Ireland, and to bring its Church into subservience to Rome. The Pope was Adrian IV., the first, and the only, Englishman who ever held that highest spiritual honour. His behests were willingly and easily obeyed. Ireland, divided between several local chieftains, or kings, did not resist Henry's armies long; and so became subjugated to England. And by thus bringing Ireland into the fold of the Church Henry made some atonement to Rome for that infamous murder, in Canterbury Cathedral, of the Archbishop Thomas, sometimes called à Becket, which was done by some of his knights who thought to give him pleasure by its doing, even if he had not directly bidden it.