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 monarchy, 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 Anglo-Dutch pro-Protestant groups in the 1688 Glorious Revolution, most of the Irish Army units stayed loyal to him and fought on his side as Jacobites in the Williamite–Jacobite War of 1688-1691. Following James's defeat, many of these units 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.