https://en.wikipedia.org/wiki/The_Pale_(Ireland)

The Pale was a strip of land that stretched north from Dalkey in Dublin to Dundalk in Louth; it became the base of English rule in Ireland. The Norman invasion of Ireland, beginning in 1169, created the Lordship of Ireland and brought Ireland under the theoretical control of the Plantagenet Kings of England. From the 13th century onwards, English rule in Ireland at first faltered, then waned. Across most of Ireland, the Anglo-Normans increasingly assimilated into Irish culture after 1300. They made alliances with neighbouring autonomous Gaelic lords. In the long periods when there was no large royal army in Ireland, the Anglo-Norman lords, like their Gaelic neighbours in the provinces, acted essentially as independent rulers in their own areas.