Henry Plantagenet, possessor of vast lands in Britain as well as France, had already been given Ireland--ceremonially--by the English pope Adrian IV in 1155. But with few resources then to spare for such a campaign, Henry simply accepted the homage offered by Dermot and authorized his other vassals to come to MacMurrough's aid. A band of Norman nobles holding lands in Wales, led by Richard fitz Gilbert de Clare--better known as "Strongbow"--crossed from Bristol to Ireland, and between 1169 and 1171 Henry's vassals conquered Leinster for MacMurrough, captured Dublin, and harried Meath. Upon Dermot's death in 1171, Strongbow took over his kingdom, prompting Henry to change his mind and condemn his vassals' activities. Fearing the potential of an independent Norman kingdom to his west, Henry cut off Strongbow's supplies and launched his own invasion. Without a fight, Henry received the submission of Strongbow and his fellow Norman adventurers as well as hostages from most of the Irish chieftains. As the new overlord of Ireland, Henry held Dublin and the eastern ports and fortresses himself, and granted Leinster to Strongbow as a fief.

One of Henry's first actions as King of Ireland was to initiate church reform. The papacy had been suspicious of Christianity in Ireland since the early fifth century, when it sent Palladius to prevent the spread of Pelagianism there. Patrick, most likely sponsored directly by the British church, brought his mission to Ireland in the middle of the century and introduced the Irish to monasticism. They were enthusiastic converts, and by the middle of the sixth century great monastic schools were founded throughout the island. This was the so-called Age of the Saints in the Celtic churches, and Ireland alone produced such giants as Brigid, Brendan, Columba, and Columbanus. The paruchia Columcille, St. Columba's family of monasteries and churches, stretched from Kells to the Scottish Hebrides, and powerful (not to mention colorful) abbots resided over centers like Clonfert, Durrow, and Iona.

Many have observed the influence of native organization and the pre-Christian filid (men of learning) on the Irish church. La Tène artistic motifs were also evident in decorated chalices, illuminated manuscripts, and standing stone crosses. The earliest secular Irish literature was filled with imrama, sea adventure stories, which had their spiritual counterpart in the peregrinatio, the dangerous pilgrimages upon which Irish holymen would embark. Asceticism also characterized the early Irish church, as one can see from the Irish penitentials which became widespread on the Continent. Missionary work, attributed to both Columba and Columbanus, would bring this characteristic Irish Christianity and learning to England, Gaul, Switzerland, and Germany.

The Viking invasions, however, hit the Irish monastic foundations particularly hard. Isolated communities like Iona were especially vulnerable, and their destruction at the hands of the Ostmen sent the Irish church into decline. Ireland before the Ostmen set up their trading posts along the east coast had no real cities, and only Armagh, the traditional seat of St. Patrick, had a dominant bishop. Rural abbots held most of the authority--and the money--and English and Continental reformers were suspicious of them and their "families" (Ireland had neither formal parishes nor mandated clerical celibacy). Archbishops of Canterbury like Lanfranc and Anselm established dependent sees in Ostman cities like Dublin in the early ninth century, and European religious orders were imported to Ireland (first Augustinian houses, then Cistercian in 1142). The Irish kings played their part as well, presiding over national synods and supporting the construction of Romanesque churches at places like Cashel.

When the Normans arrived in Ireland, then, they found a few fledgling metropolitan bishops trying to bring Ireland "up to speed" with Continental religious developments. Real Anglo-Norman colonization began shortly after Henry II's visit, with new towns appearing in the east where nobles spoke Norman-French and peasants spoke English. Henry's son John, whom he had formally recognized as lord of Ireland, laid the foundations of royal (English) government in the island with the establishment of the King's Council in Ireland and a Treasurer of Ireland, while Anglo-Norman bishops were installed in all dependent sees.

What emerges from this first attempt at colonial government in Ireland is essentially an eastern seaboard controlled directly by the English kings, surrounded by "liberties" held by Norman barons on whose western and northern borders lay the independent Irish chiefdoms. Eventually many of these Norman baronial families adopted the Irish language and customs, rebelling against royal authority as regularly as did the native Irish chiefs (thirteenth and fourteenth century sources are full of accounts of these revolts). English writers became increasingly hostile to these Irish "barbarians" (Snyder 1996), and with the Statututes of Kilkenny in 1366 the English government tried to stop the process of "degeneration" among the Anglo-Irish by forbidding colonists to adopt Irish customs.

It was, of course, too late. A cultural boundary was being established which divided the quarrelsome Irish majority from the politically and commercially potent English minority. This strip of land around Dublin, which came to be known as the Pale, would control the political and religious fortunes of the rest of the island for several centuries to come.