St. patrick converted the Celtic tribes of Ireland to Christianity in the fifth century. Irish missionaries then went out to Scotland, England, and Europe and, while Rome disintegrated, Ireland stood as a cultureal, religious, and educational center. But the Viking invasion changed Ireland: the destruction wrought in the 9th and 10th centuries left ireland isolated and poor. In 1014, Brian Boru reestablished an Irish monarchy. A century later, England turned its eye to Ireland as henry II became overlord. Eventually, another Henry -- the Eighth -- would declare himself monarch of Ireland as well. Henry brought the Reformation to Ireland at great hardship to the Catholic country. The Catholic Mass was made an act of treason. When rebellion arose in 1641, it was crushed by Cromwell over the course of a ten-year struggle, ending with the terrible massacre at Drogheda. The Irish supported James II against William of Orange, butJames was defeated at the Battle of the Boyne in 1690, which sealed Ireland's fate as England imposed desctructive economic sanctions on the country as a result. The Gaelic language declined until few spoke it and the Irish aristocracy largely fled into exile. But the Irish kept trying, mounting an uprising in 1798 with held from Frnace, then in the throes of its own revolutionary fervor. The rebellion failed, with enormous casualities. Two years later, the Act of Union joined Ireland to England. But in response to continued agitation, England enacted the Catholic Emancipation Act in 1829. In the 1840s, the potato blight led to the deaths of at least a million people from starvation and the emigration of at least 1.6 million more. Eventually, the English developed a plan that would create Northern Ireland, composed of six counties, that would be a part of the United Kingdom. The southern counties would have no part of this plan and they became independent within the Commonwealth. In 1949, Ireland became a fully-independent republic and Eamon de Valera prime minister; he was elected president of the republic in 1959. Ireland has been deeply involved in trying to mediate the problems of Northern Ireland, long mired in sectarian violence. While Ireland prospered in the south, the North suffered from thousands of casualties. Over the 1980s and 1990s, myriad attempts to negotiate an acceptable agreement raised hopes, but not until 1998 was an accord reached that promised the beginning of the end to violence.