The Viking period in Ireland began in the late eighth and persisted until the tenth century. Ireland was relatively accessible from the North Sea, whence the Vikings sailed on multiple raids. Fundamentally, the Vikings were plunderers, "but they brought away what was still more valuable to those who followed . . . tales of bright green fields, of rich fertile soil . . . a land that was well worth fighting for" (MacManus 268-269). In the mid-ninth century, Norwegian and Danish Vikings used the village of Dubhlinn (Dublin) as base of operations for raids and settlement. A Norwegian king, Tuirgeis, desired to supplant Christianity with Norse paganism, but his defeat by the Irish King Malachy, as well as rival Danish raiders more friendly toward Christianity, began to turn that tide. Danish, Irish, and Norwegian warlords skirmished for Ireland's coastal and inland river villages for some 200 years, by the end of which a combination of petty warfare and marital alliances in all social strata had yielded a species of civil society. The battle of the Weir of Clontarf, between indigenous Irish and the Danes, seems to have been decisive in that regard. Meanwhile, however, cross-cultural dynamics took place, with the Vikings learning agriculture and fine craftsmanship from the Irish, teaching them shipbuilding, fortification, and foreign trade, and imparting both family and place names, such as Erin and Ireland, which come from Old Norse language (MacManus 284).
The Christian invasion of Ireland is associated with a 5th-century British bishop named Patrick, who initially seems to have been abducted to Ireland by pirate slavers and who returned to Ireland many years after escaping, in order to "organize[] a national church along episcopal lines in a country which was not yet united" (Williams 95). There was a Christian presence, colored by the Pelagian heresy, but Patrick was orthodox in mission ("Church"). His main religious rivals were the ...