Synod of Kells 1152
The period after the Viking invasion was a time of recovery for religion and culture, in spite of the disturbed political life of the country. The Irish Church was reformed and reorganized into dioceses. At the Synod of Kells in 1152, the country was divided into 36 dioceses, and grouped into 4 provinces under the archbishops of Armagh, Dublin, Cashel, and Tuam. St. Malachy of Armagh was the greatest of the religious reformers and introduced the Cistercian Order into Ireland. In 1142, the first Irish Cistercian monastery Mellifont Abbey was founded in County Louth.
Many of Bishops Seats where hereditary between 1000 and 1100's, the economy of the country was mainly pastoral. A person's wealth was reckoned by the number of cattle he or she owned. The social unit was still the Tuath, which was based on family groups. The ruler of a Tuath lived in a fortified house called a rath, or dun, together with a brehon (lawyer), minstrel, physician, and several craft-workers. The ruler's subjects lived in huts of wattle and clay. The people were poorly armed and no match for the warlike Normans who invaded Ireland in the latter part of the 1100's.
Between November 1155 and 1156, John of Salisbury a friend of Theobald of Canterbury, Thomas Beckett, and Bernard of Clairvaux, spent three months with Pope Adrian IV (Nicholas Breakspear, the only English Pope) and persuade the Pope to issue the 'Bull Laudabiliter' which gave full Papal approval for the Anglo Norman invasion of Ireland.
In 1153 Dermot McMurrough, king of Leinster attacked the lands of Tiernan O'Rourke, king of Breifne (Leitrim Cavan area) he carried off large numbers of livestock, as well as O'Rourke's wife Dervorgilla, opinions differ as to whether or not she went willingly, however she was eventually returned.
In 1156 Turlough O'Connor king of Connacht died, Murtagh MacLoughlin, king of Ulster, with the help of Dermot McMurrough, king of Leinster, made himself king of Ireland. Ten years later, he was overthrown, and Turlough's son, Rory O'Connor, became the one who was to be the last native king of Ireland.
Eventually in 1166 MacMurrough was expelled from Ireland by Roderick (Rory O'Connor) high king of Ireland. MacMurrough went to England where he sought help from King Henry II. Henry eagerly seized the opportunity of expanding his kingdom and gave gave him permission to enlist several Anglo Norman Lords, the chief of which was Richard FitzGilbert de Clare (Strongbow) MacMurrough promised his daughter Aoife's hand in marriage to Strongbow as well as succession to his kingship of Leinster.