Norman invasion of Ireland

The Norman invasion of Ireland took place in stages during the late 12th century, at a time when Gaelic Ireland was made up of several kingdoms, with a High King claiming lordship over all.

In May 1169, Cambro-Norman mercenaries landed in Ireland at the request of Diarmait Mac Murchada (Dermot MacMurragh), the ousted King of Leinster, who had sought their help in regaining his kingdom. Diarmait and the Normans seized Leinster within weeks and launched raids into neighbouring kingdoms. This military intervention had the backing of King Henry II of England and was authorized by Pope Adrian IV.

And there and then the high king stood strong and lay down too led by Richard 'Strongbow' de Clare. By May 1171, Strongbow had assumed control of Leinster and seized the Norse-Irish city kingdoms of Dublin, Waterford, and Wexford. That summer, High King Ruaidrí Ua Conchobair (Rory O'Connor) led an Irish counteroffensive against the Normans, but they managed to hold most of their conquered territory. In October 1171, King Henry landed a large Anglo-Norman army in Ireland to establish control over both the Cambro-Normans and the Irish. The Norman lords handed their conquered territory to Henry. He let Strongbow hold Leinster in fief and declared the cities to be crown land. Many Irish kings also submitted to him, likely in the hope that he would curb Norman expansion. Henry, however, granted the unconquered kingdom of Meath to Hugh de Lacy. After Henry's departure in 1172, Norman expansion and Irish counteroffensives continued.

The 1175 Treaty of Windsor acknowledged Henry as overlord of the conquered territory and Ruaidrí as overlord of the rest of Ireland, with Ruaidrí also swearing fealty to Henry. However, the Treaty soon fell apart; the Anglo-Norman lords continued to invade Irish kingdoms and they in turn launched counter-attacks. In 1177, Henry adopted a new policy. He declared his son John to be "Lord of Ireland" (i.e. of the whole country) and authorized the Norman lords to conquer more land. The territory they held became the Lordship of Ireland and formed part of the Angevin Empire. The largely successful nature of the invasion has been attributed to a number of factors. These include the Normans' military superiority and programme of castle-building; the lack of a unified opposition from the Irish; and the Church's support for Henry's intervention.

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