In the 16th century the Tudor monarchs began a reconquest of Ireland. Henry VIII declared himself king of Ireland in 1541, the first English monarch to do so. The Tudors introduced new English settlers and embarked on a series of military campaigns against the Gaelic Irish and the great Anglo-Norman lords who had fallen away in their allegiance to the Crown. When the army of Elizabeth defeated the Irish at the battle of Kinsale in 1601, it marked the beginning of a new order. The native political system was overthrown and for the first time the entire country was run by a strong English central Government.
From the 16th century onwards the English Government made strenuous efforts to impose Protestantism. The reformed religion did not really take root, however, partly due to its close association with the repressive policies of the English administration. The main exception was in Ulster where the Government promoted a successful colonization by new settlers, mostly Scottish Presbyterians.
Religion added complexity to the political situation. The new colonists were Protestant and formed a distinct group from the Old English, the remnants of the Anglo-Irish colony who were still Catholic and increasingly disaffected from the Government. To a large extent political power and office were now in the hands of the colonists, the New English. When the Gaelic Irish of Ulster rebelled against the Government in 1641 they were soon joined by their Old English co-religionists. In 1642 a rebel assembly, the Confederation of Kilkenny, met, but divisions soon appeared as Ireland became enmeshed in the English civil war between King and Parliament. The rebellion was ruthlessly crushed by Oliver Cromwell and his parliamentary army.
Further Protestant colonization took place under Cromwell. This time the large-scale confiscation of land and the banishment of its former owners to the poorer areas of the country ensured that property and political power passed to the new colonists. The accession of the Catholic King James II in 1685 changed the situation only temporarily. His pro-Catholic stance was unpopular in England and Scotland and among the Ulster Scots. When William of Orange challenged James II for the throne the entire country except Ulster backed James. The two kings contested their throne in Ireland and William emerged victorious after a series of battles, the most famous being Williamís defeat of James at the Boyne in 1690. Williamís victory left the Irish Catholics politically helpless and made possible the Protestant ascendancy that followed. Many leading Catholics like Patrick Sarsfield (Jamesí commander-in-chief) went abroad to serve in continental armies.