The Normans were originally from the Normandy area of north-west France. They had conquered England in 1066 and became known as Anglo-Normans. They arrived in Ireland in 1169 with conquest in mind. At this time the Wicklow uplands were, for the most part, unoccupied. This fact was exploited by Strongbow, the leader of the Normans, when in 1170 he advanced from the south-east towards Dublin. Anticipating a lowland advance, Gaelic troops lay in wait for the army. By taking an upland route through the mountains via Glendalough, the Norman soldiers succeeded in bypassing the Irish and gaining access to Dublin.
The Anglo-Normans were militarily superior to the native Irish and they succeeded in wresting much of the eastern part of the country from the Gaelic tribes. They established their own administrative structures in areas under their control. They divided their territory into counties, the divisions which are still used today. The creation of counties proceeded as the Norman advanced but the inhabitants of the Wicklow uplands never fell under Norman control.
Norman advance into an area was characterised by the early construction of fortified, defensive structures. Typically the initial structures were motte or motte and bailey constructions. Later, with military supremacy in an area secured, stone castles and manors followed. Both the coastal strip from Dublin to Wicklow town and the western plateaus and plains proved attractive settlement sites for the Normans whilst the unproductive lands at higher altitudes were ignored. Strong Norman settlements, including castles and manor houses, were established at Bray, Newcastle, Powerscourt, and Wicklow in the east, and at Imaal and Hollywood in the west.
Originally, the Wicklow Mountains were part of County Dublin. Although close to the capital, the mountains afforded protection to the native Irish tribes. A lowland/upland division based on ethnicity emerged, with the Anglo-Normans inhabiting the good low-lying lands, and the Irish inhabiting the poorer mountain areas.
Two great Wicklow clans, the O'Byrnes and O'Tooles, originally from County Kildare, moved to the Wicklow mountains at this time, in response to warring Irish tribes and the land-hungry Norman invaders. These two clans became a long-standing thorn in the side of the new Anglo-Norman order. Geographically the O'Byrnes were powerful in the eastern parts of the uplands with the O'Tooles based in the south and west. Their presence in inhospitable territories presented challenges to the new authority. In the first instance the presence of armed, Gaelic tribes greatly aggravated the difficulties involved in trans-mountain communications. Secondly, the Gaelic tribes frequently harried the lowland settlers, often attacking their manors, located to their north, east and west.
By 1270 the O'Tooles were firmly ensconced at Glenmalure and successive government raids against the clan were unable either to dislodge them or to seriously weaken their power. It was about this time, probably as a result of harvest failures, that a series of rebellions commenced and the situation was so troubling that large armies were mustered to march against Glenmalure. During the early 1270s tensions were heightened and although ultimate victory eluded the Irish, some notable successes were scored. Unrest continued, especially during the winter months when times were particularly hard for the poor upland farmers. By the commencement of the fourteenth century the manorial system in the lowlands was under sustained pressure from attacking Gaels.
Throughout the fourteenth century, there were countless battles and atrocities in the Wicklow Mountains and hardly a year passed without a government inspired expedition being launched against the Irish. Spanning the Bruce's invasion and defeat (1315-18), the impact of the Black Death (1348) and the arrival of Richard II (1394 and 1399), the Wicklow clans maintained a stubborn resistance to government. In fact, throughout the century, Gaelic power reasserted itself to a degree, and the English colony was in a worried state. It is unsurprising, therefore, that the English attacked and burned Glendalough in 1398.
By the middle years of the fifteenth century the English colony had been dramatically reduced in size and now comprised a small pocket of land in the vicinity of Dublin. This area, known as the Pale, was subject to continuous threat from the Irish clans, principally those based to the south. As the Norman sphere of influence in the Wicklow area shrank northwards, their abandoned sites were occupied by the Gaels. From the end of the fourteenth century the settlers had been effectively driven from Wicklow.