James II, however, reversed the policy of Charles II. Under James's viceroy in Ireland, Richard Talbot, Earl of Tyrconnel, Roman Catholics were advanced to positions of state and placed in control of the militia, which Ormonde had previously organised. Consequently, the entire Roman Catholic population sided with James II in the so-called Glorious Revolution of 1688. Thus, in 1689, when James landed at Dublin with his French officers, Talbot had an Irish army ready to assist him. 

The Protestant settlers were driven from their homes and found refuge in the towns of Enniskillen and Derry, which James attempted to capture. He was hampered by his lack of artillery, however, and the latter was relieved by sea. His parliament of 1689 restored all lands confiscated since 1641 and passed an act of attainder against the partisans of William III. 

In the following year William landed in Ireland and, in July 1690, in the Battle of the Boyne, he defeated the Irish forces. He failed, however, to capture the town of Limerick, which was bravely defended. A brilliant tactic of the Irish patriot Patrick Sarsfield destroyed William's heavy artillery, and he was forced to retire. 

The next year, William's generals defeated the Irish army at the town of Aughrim, and Limerick was forced to capitulate. By the terms of the Treaty of Limerick (1691), Roman Catholics were permitted a certain amount of religious freedom, and the lands that Roman Catholics had possessed under Charles II were to be restored to them. 

The parliament of England subsequently forced William to break the concession of the Treaty of Limerick regarding the restoration of the land, and the parliament of Ireland violated the terms granting religious toleration by enacting Penal Laws (or Popery Laws) directed against the Roman Catholics. Irish commerce and industries were deliberately crushed by the English. By enactment in 1665 and 1680 the Irish export trade to England in cattle, milk, butter, and cheese had been forbidden. The trade in woollens, which had grown up among the Irish Protestants, was likewise crushed by an enactment of 1699, which prohibited the export of woollen goods from Ireland to any country whatever. 

Small amends for these injuries were made by leaving the linen trade undisturbed. The result of these measures was gradual economic decline. Many Irish emigrated from the country-the Roman Catholics largely to Spain and France, the Protestants to America.