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][5] 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.

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

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

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).

[14][15] 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.

Although most of them were not considered well enough trained to go into camp during the summer of 1804, a few regiments did, including the Leitrim, which was part of a large encampment at the Curragh, outside Dublin.

[21] 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.

Although ballots might still be held, the regiments were rarely assembled for training and the permanent staffs were progressively reduced.

Although many younger officers were appointed to the reformed militia, the Earl of Leitrim and Lt-Col Clements retained their positions.

[4][5][25] By early March 1855 the regiment was embodied at Mohill,[29] moving to Longford during June,[30] and then to Cork in November.

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

For the Leitrim Militia this was in Sub-District No 68 (Counties of Leitrim, Sligo, Roscommon, Mayo, and Galway) in Dublin District of Irish Command:[33][37] 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 Leitrim Rifles was assigned to the Garrison Army manning a range of small forts and posts across Ireland.

[4][5][33] The Rifle Brigade Depot was at Peninsula Barracks, Winchester, but the militia battalions retained their own headquarters.

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