Ireland comprises major cities like Limerick, Galway, Cork, and Dublin, each with a significant role in international affairs. The island is politically divided into two parts: the Republic of Ireland (Eire), which is an independent republic, and Northern Ireland, a British province governed from Britain. The Republic of Ireland has a population of approximately 3 million, with about 95% identifying as Catholics.

In contrast, Northern Ireland has a population of 1.5 million, with around 60% being Protestants and 40% Catholics. Historically, Ireland was a collection of shifting kingdoms and over-kingdoms, where regional dynasties vied for supremacy over the entire island. King Diarmait Mac Murchada of Leinster, one of these regional rulers, was exiled by the new High King, Ruaidri mac Tairrdelbach Ua Conchobair of Connacht. Diarmait sought Norman knights' assistance to reclaim his kingdom, gaining permission from Henry II of England.

The Norman invasion of Ireland began in 1167 when the first Norman knight arrived, followed by larger forces of Normans, Welsh, and Flemings. Diarmait regained control of several counties and designated his son-in-law, Norman Richard de Clare (known as Strongbow), as his heir. This alarmed King Henry II, who feared the establishment of a rival Norman state in Ireland. Henry decided to assert his authority.

The Norman invasion of Ireland began in 1167 when the first Norman knight arrived, followed by larger forces of Normans, Welsh, and Flemings. Diarmait regained control of several counties and designated his son-in-law, Norman Richard de Clare (known as Strongbow), as his heir. This alarmed King Henry II, who feared the establishment of a rival Norman state in Ireland. Henry decided to assert his authority.