This post will aim to give a concise overview of the component parts of the British Army between, for the sake of convenience, 1881 and 1918.
The Regular Army
Until July 1881 the majority of infantry regiments had been designated as Regiments of Foot but by July 1881 these designations had been swept away and replaced with 'territorial' or county titles. This was all part of Secretary of State for War Edward Cardwell's army reforms, carried through in 1881 by his successor, the then Secretary of State for War, Hugh Childers.
The first 25 Regiments of Foot were all two-battalion regiments but the Regiments of Foot from the 26th Foot onwards were all single battalions which were now paired with another battalion. Thus, for example, the 26th (Cameronian) Regiment of Foot was paired with the 90th Regiment of Foot (Perthshire Volunteers) to form The Cameronians (Scottish Rifles). This was a logical pairing of two Scottish regiments whereas the pairing of the 27th (Inniskilling) Regiment of Foot with the 108th (Madras Infantry) Regiment of Foot to form the Royal Inniskilling Fusiliers made no sense at all to many an outraged retired colonel.
Men joining the army enlisted for 12 years in total, this term comprised of colour service and reserve service. The periods of colour and reserve service varied according to the corps the man signed up with, and according to when he signed up. Typical terms of enlistment with the infantry were seven years with the colours and five years on the reserve. A man served his first seven years in army uniform but when he was transferred to the reserve he handed in his uniform and returned to civvy street, albeit with the liability to be recalled to the colours if his country needed him. Men were recalled from the reserve in 1899 and in 1914.
Regular regiments typically had two battalions, one serving at home in the United Kingdom and one serving overseas. However, this being the British Army there were exceptions to every rule. The Cameron Highlanders was a single-battalion regiment until 1897 whilst there were a number of regiments which had four battalions at different points in time.
The militia was seen by many young men as a good testing ground for military life. By 1881 each infantry regiment had between one and three (in Ireland) militia battalions comprised of men who committed to serve a term of six years in total. The militia trained with and shared a depot with the infantry regiment and both the militia and the regular battalions were funded and governed by the War Office.
Militia commitment was very much a local and a part-time affair. New recruits signed up to serve in the county in which they were resident and typically drilled for 49 days on enlistment before returning to their civilian lives. Their only commitment thereafter was regular training and an annual two-week camp.
The militia could be embodied for war service and this happened in 1899, forty militia battalions being approached to volunteer.
The Militia Reserve
The militia reserve was a reserve for the regular army. It consisted of militia-men who, in return for a bounty of £1 a year, committed to remain with the militia either six years or the whole time of their service. In the event of war they were to enter the regular army on the same terms as men on the army reserve men and could be sent anywhere in the world and assigned to any regiment to which the army deemed it fit to send them.
The Volunteer Force & Territorial Force
The Volunteer Force (VF) was established in 1859 and quickly grew as a citizen army managed and funded by local worthies rather than the War Office. In 1908 the VF was superseded by the Territorial Force (TF), run by County Associations which, nonetheless, had no jurisdiction over their operational deployment. Men joining the TF did so for four years, and for service in the United Kingdom only, although they could also volunteer to serve overseas. Ireland had no Territorial Force battalions. As indicated, the TF was organised on a county level although some battalions found themselves being administered by more than one county association. The 5th, 6th and 7th Battalions of the Royal Welsh Fusiliers, for instance, were each administered by two different county associations.
The Special Reserve and Extra Reserve
The Special Reserve replaced the militia in 1908, just as the Territorial Force replaced the Volunteer Force in the same year. Men joining the Special Reserve enlisted for six years' service but with the understanding that in the event of war they could be sent out as part of draft to replace casualties in the regular battalions. The Special Reserve attracted men who had no prior military service and, later, men who were time-expired regulars. See this post of mine detailing the Special Reserve attestation form to be used.