Irish Army (1661–1801)

The Irish Army or Irish establishment, in practice called the monarch's "army in Ireland" or "army of Ireland", was the standing army of the Kingdom of Ireland, a client state of England and subsequently (from 1707) of Great Britain. It existed from the early 1660s until merged into the British Army in 1801, and for much of the period was the largest force available to the British Crown, being substantially larger than the English and Scottish establishments. Initially solely under the monarch's control, from 1699 the army was jointly controlled by the monarch and by the Parliament of England. The Parliament of Ireland took over some responsibilities in 1769, extended after 1782 when it began passing its own Mutiny Acts. The army, funded by Irish crown revenues, had its own Commander-in-Chief.

For much of its history, only members of the Anglo-Irish Anglican Protestant minority could join the army, while both the Catholic majority in Ireland and Protestant Nonconformists were barred from enlistment. During the reign of the Catholic king James II (r. 1685–1688), Catholics were actively recruited into the army and quickly became a majority within it. When James was overthrown by in the 1688 Glorious Revolution, most Irish Army troops stayed loyal to him and fought on his side as Jacobites in the Williamite War in Ireland. Following James's defeat, many of these troops went into exile in France, where they became the core of the Irish Brigade.

The army was rebuilt by the new regime after the Williamite victory, once again as an exclusively Protestant force, although manpower shortages meant that over time some Catholics were enlisted, an arrangement finally legalised in 1778. Its soldiers fought for Britain in the Nine Years' War of 1688–1697, the French and Indian War of 1754–1763, and the American Revolutionary War of 1775–1783. It also fought against the United Irishmen insurgents in the Irish Rebellion of 1798, although the bulk of the pro-Government fighting was left by the establishment to be done by two parallel but separate forces intended for service domestically: the Irish Militia, re-organized in 1793, and the Irish Yeomanry, formed in 1796.

Following the 1800 Acts of Union and their abolition of the Parliament of Ireland, the Irish Army's regiments were placed on the British establishment, although some roles continued to exist separately. For historical reasons, the modern Irish Army, which originated as the pre-1922 Irish Republican Army, does not trace its lineage from any part of the earlier Irish Army, although the pre-1922 Royal Irish Regiment did, while the 92nd Regiment of the French Army still traces its descent from the Irish Brigade.

Following the Anglo-Norman invasion of Ireland in the late 12th century, large parts of Ireland came under the control of Anglo-Norman lords and the English Crown. This territory became the Lordship of Ireland and the kings of England claimed sovereignty over it as "lords of Ireland". The rest of the island—known as Gaelic Ireland—remained under the control of various native Irish kingdoms and chiefdoms. The English administration, the Anglo-Norman lords and the Irish chiefs each raised their own armies in times of war.

By the 15th century the area of direct English control had shrunk to an area called the Pale, and English rule came under further strain during the rebellion of Thomas FitzGerald, 10th Earl of Kildare in the 1530s. The Fitzgerald family had traditionally been the leading Anglo-Irish lords in the country, serving as Lord Lieutenants. Their rebellion exposed the weakness of Henry VIII's forces in the Lordship, with the rebels securing large gains and besieging Dublin.

In 1542 the Kingdom of Ireland was formally established and Henry VIII of England became King of Ireland. The English then began establishing control over the island. It involved the policy of surrender and regrant, and the colonization of Irish land by Protestant settlers, largely from England. This sparked conflict with various Irish lordships, most notably the Desmond Rebellions and the Nine Years' War. This latter conflict ended in 1603 with English victory over the Irish armies and their Spanish allies. Following the Flight of the Earls (1607), all of Ireland came under the control of the English Crown and its government in Ireland.

During the Scottish Crisis of the early 1640s, Randal MacDonnell, Earl of Antrim was authorized by King Charles I to raise a 'New Irish Army'. Mainly drawn from the Catholic Gaelic inhabitants of Ulster, and mustered at Carrickfergus, it was intended to take part in a landing on the coast of Scotland. However it was rumoured that Charles I planned to lead the New Irish Army against his English Parliamentarian enemies, in the months before the outbreak of the English Civil War. When the Irish Rebellion of 1641 broke out, the traditional Irish Army was too small in size to cope. Many soldiers of the New Irish Army joined the rebels, and soon controlled large swathes of Ireland. In 1642 they established the Irish Catholic Confederacy and an Irish Confederate army.