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.

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.

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.

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.

[9] Many of its officers and men were, however, Cromwellian veterans of doubtful loyalty, and in 1661 Charles's newly appointed viceroy, the Duke of Ormonde, began a process of reforming it.

[10] The experienced Anglo-Irish soldier Sir William Flower was made lieutenant-colonel, while Ormonde's son Richard Butler, 1st Earl of Arran was gazetted colonel, with captaincy of a company.

[11] In 1672 the remainder of the Irish army was organised into six new regiments of foot, though this was primarily a paper-based exercise as other than the Guards they remained split up in small garrisons around the country.

[3] While the Royal Hospital Kilmainham was built for the welfare of soldiers in 1680,[12] the rank and file remained generally poorly paid and equipped; a report of 1676 described the army as "in a most miserable condition".

[18] He also began accelerating recruitment of Catholics into the rank and file, starting with the Foot Guards, giving the pretext that “the King would have all his men young and of one size”.

[22] With the implications for Ireland uncertain, Irish Protestants launched a rebellion in 1689, forming the Army of the North and declaring William as king, though Tyrconnell was able to retain control of most towns using the remaining units loyal to James.

After initially considering reaching a peace settlement with William, Tyrconnell subsequently resolved to hold Ireland for James; in January 1689 he issued warrants for an enormous expansion of the army.

[24] As the Catholic gentry realised the profits that could be made raising men for military service, many of the new regiments initially consisted of 30-45 companies, mostly without uniforms and armed with clubs or rusty muskets; neither Tyrconnell's government nor the Irish economy could afford to properly equip or pay such numbers and a team of inspectors, including Patrick Sarsfield, reduced them to more manageable totals.

[25] James landed in Kinsale on 12 March, accompanied by French regulars under Conrad von Rosen, along with English, Scottish and Irish Jacobite volunteers, in an attempt to use Ireland as a base to regain all three kingdoms.

[27] Carrickfergus fell on 27 August, but an opportunity for Schomberg to quickly end the war by taking Dundalk was missed after his army was crippled by poor logistics, exacerbated by disease.

In October Sarsfield signed the Treaty of Limerick; the settlement agreed to his demand that those still in Jacobite service could leave for France to serve with the French army.

[30] Modern estimates suggest that around 19,000 men of the Irish army and rapparees, or irregular forces, departed: women and children brought the figure to slightly over 20,000, or about one per cent of Ireland's population at the time.

[36][34] Through most of the 18th century, parliamentary hostility in England to a large standing army meant that the Irish military establishment continued in use as a means to preserve a cadre of regiments that would otherwise have been disbanded.

[40] The inequities of the situation were among the main drivers of the early Irish Patriot movement in the mid 18th century; it was pointed out that Ireland was "obliged to support a large [...] military establishment" primarily for the benefit of Great Britain, while still being subject to restrictions on trade.

[41] The British government drew on regiments on the Irish establishment for the Braddock Expedition to Fort Duquesne at the opening stages of the French and Indian War.

Despite this, the Volunteers rapidly emerged as a political movement demanding greater powers be granted to Ireland by London, which eventually led to the Constitution of 1782.

[citation needed] This came at a time of growing support for the republican ideas of the French Revolution, amidst fears of the revolutionary spirit spreading to Britain and Ireland.

By this stage the traditional ban on Irish Catholics serving in the army had been completely removed, and they began to supply a growing portion of troops.