During the 18th Century there were various Volunteer Associations and unofficial militia units controlled by the landowners, concerned mainly with internal security.

While most of the Regular Army was fighting overseas, the coasts of England and Wales were defended by the embodied Militia, but Ireland had no equivalent force.

The new Act was based on existing English precedents, with the men conscripted by ballot to fill county quotas (paid substitutes were permitted) and the officers having to meet certain property qualifications.

[4] George Nugent, 7th Earl of Westmeath, was appointed Colonel on 25 April 1793, with Sir Hugh O'Reilly (created 1st Baronet in 1795), as Lieutenant-Colonel with seniority from the following day.

[5][6] The French Revolutionary and Napoleonic Wars saw the British and Irish militia embodied for a whole generation, becoming regiments of full-time professional soldiers (though restricted to service in Britain or Ireland respectively), which the regular army increasingly saw as a prime source of recruits.

They served in coast defences, manned garrisons, guarded prisoners of war, and carried out internal security duties.

[7] In Ireland the latter role assumed greater importance, with frequent armed clashes between militia detachments and the self-styled 'Defenders' in the 1790s.

[9] In 1795 the new Lord Lieutenant of Ireland, the Earl of Camden, introduced summer camps to give the militia field training in larger formations.

He personally read the Articles of War to his men after Sunday services, stressing the penalties for 'profane cursing and swearing'.

A large French expeditionary force appeared in Bantry Bay on 21 December and troops from all over Ireland were marched towards the threatened area: the Westmeath was sent from Limerick.

When the militiamen of 1793 reached the end of their four-year enlistment in 1797, most of the Irish regiments were able to maintain their numbers through re-enlistments (for a bounty).

[15] Meanwhile, the main body of the regiment was stationed at Clonakilty in West County Cork under the command of Lt-Col Sir Hugh O'Reilly.

The regiment, 220 strong with its two 6-pounders, was ordered to march to Bandon, but approaching Ballynascarty on 19 June it was attacked at a crossroads by a body of 3–400 rebels, mainly armed with pikes, coming down the hillside on the left of the column.

The Battle of the Big Cross, as it became known, resulted in the loss of one sergeant and one private of the Westmeaths, and a reported 130 rebels killed.

Each detachment comprised one subaltern, one sergeant, one corporal and 20 picked men, who received extra pay for the work.

[22] By the end of 1801 peace negotiations with the French were progressing and recruiting and re-enlistment for the Irish Militia was stopped in October.

Over the following years the regiments carried out garrison duties at various towns across Ireland, attended summer training camps.

[29] Napoleon escaped from Elba in 1815 and the Irish Militia were called out again on 26 June as the bulk of the regular army crossed to the Continent for the short Waterloo campaign and occupation duties in its aftermath.

The Militia Reserve introduced in 1867 consisted of present and former militiamen who undertook to serve overseas in case of war.

For the Westmeath Militia this was in Sub-District No 67 (Counties of Meath, Westmeath and Longford, and King's and Queen's Counties) in Dublin District of Irish Command:[41] Although often referred to as brigades, the sub-districts were purely administrative organisations, but in a continuation of the Cardwell Reforms a mobilisation scheme began to appear in the Army List from December 1875.

The Westmeath Militia was assigned to the Garrison Army manning a range of small forts and posts across Ireland.

This large regiment now consisted of:[4][41] Formally, the regiment became the 9th (Westmeath Militia) Battalion, Rifle Brigade (The Prince Consort's Own) on 1 July 1881[4][44] The Rifle Brigade Depot was at Peninsula Barracks, Winchester, but the militia battalions retained their own headquarters.

When the militia was converted into the Special Reserve under the Haldane Reforms of 1908, the 6th Bn Rifle Brigade did not transfer and was disbanded on 31 July 1908.

On the outbreak of the French Revolutionary War the English counties had drawn lots to determine the relative precedence of their militia regiments.