In 1153 MacMurrough abducted Derivogle wife of Tiernan O'Ruark, king of Breifne (Leitrim Cavan area) MacMurrough was attacked and the abducted wife returned. Eventually in 1166 MacMurrough was expelled from Ireland by Rodrick (Rory O'Connor) high king of Ireland. MacMurrough went to England where he sought help from King Henry II. Henry gave him permission to enlist several Anglo Norman Lords, the chief of which was Richard FitzGilbert de Clare (Stongbow) MacMurrough promised his daughter Aoife's hand in marrige to Strongbow

This action on the part of MacMurrough is regarded by many as the single act which led to the Anglo Norman conquest of Ireland, although it appears, and this is not accepted by all, that the church of Rome and the English monarchy held negotiations regarding a crusade to Ireland to reign in the Irish church who's doctrines and policys had diverged somewhat from those of Rome.

Strongbow Arrives in Ireland.
The year 1170 saw the landing in Waterford of Strongbow, after sacking the town with great ferocity, his next action was to marry MacMurrough daughter Aoife. He marched north and captured Dublin, then turning west he plundered Meath. In 1171 MacMurrough died and Strongbow took control of all the captured lands in the name of King Henry II

In England Henry II was paying close attention to the unfolding events in Ireland, perhaps fearful that Strongbow would gain too much power, he decided to take his own army to Ireland, on 7th October 1171 they disembarked from four hundred ships, 3,500 men at arm and archers as well as five hundred knights. Upon the arrival of Henrys army most of the Irish Prince's and provincial kings accepted Henry as their ruler apart from Tyrconnel of Tyrone.

The Battle of Downpatrick.

The Anglo-Normans set about building a string of castles to consolidate their holdings. Although the Irish were scattered and leaderless they never really capitulated. In 1258 the Irish Clans remaining elected Brian ONeill as their High King in an attempt to unite the country. The clans were weak compared to the Normans and were quickly defeated in the disastrous Battle of Downpatrick in 1260. The Irish fought bravely dressed in linen while the Normans were protected by iron and fought in organized groups on horseback. ONeill was killed and their hopes of escape from Anglo-Norman oppression and greed dashed.