The British home army in the First World War served the dual purpose of defending the country against invasion and training reinforcements for the army overseas. Initial responsibility for defending the nation lay with the Territorial Force, a part-time auxiliary designed in 1908 as a means of expanding the army in a major foreign conflict but, as a result of political compromise, implemented as a home defence army. It was supported in this role by 42,000 regular army troops, primarily belonging to the Royal Garrison Artillery and the Royal Engineers. The 14 infantry divisions and 14 mounted brigades of the Territorial Force were mainly allocated either to the Local Force, stationed near the coast and tasked with disrupting an invasion at the point of landing, or the Central Force, a mobile element tasked with defeating the invading force as it marched on London. The Local Force was augmented by units of the Special Reserve and Extra Reserve, which were the third battalions of the regular army line infantry regiments established to recruit and train replacements for their regiments' two combat battalions. The home army was also largely responsible for guarding vulnerable points, such as the communications infrastructure, rail network and munitions works.
Although the territorials could not be compelled to serve outside the United Kingdom, they could volunteer to do so, and when large numbers did, units of the Territorial Force began to be posted overseas. By July 1915, the home army had been stripped of all its original territorial divisions, and their places in the home defences were taken by second-line territorial units. The new units competed for equipment with the 'New Army' being raised to expand the army overseas, the reserves of which were also allocated to home defence while they trained, and suffered from severe shortages. The second line's task in home defence was also complicated by having to supply replacement drafts to the first line and the need to train for their own eventual deployment overseas. Most of the second line divisions had departed the country by 1917, and the territorial brigades in those that remained were replaced by brigades of the Training Reserve, created in 1916 by a reorganisation of New Army reserve units.
To make up the losses, the duties of the home army were increasingly performed by personnel unsuitable for service at the front. The National Reserve, comprising men above military age with previous military experience, relieved territorials in guarding vulnerable points. It was re-organised in early 1916 as the Royal Defence Corps which, in 1917, also began to man coastal defences. Older members of the National Reserve played a leading role in the development of the Volunteer Training Corps. This was a spontaneous civilian movement which sprang into existence as soon as war was declared and assisted the home army in a variety of duties, including the digging of the London defences and the guarding of vulnerable points. The movement was initially met by the authorities with antipathy and censure, but it was formally recognised in 1916 as an official military auxiliary and incorporated, as the Volunteer Force, into the anti-invasion plans.
A shortage of manpower at the end of 1917 resulted in further significant reductions in the home army. Four of its eight divisions were disbanded, and the partially trained 19-year-olds in the remainder were replaced with raw 18-year-old recruits. The problem was exacerbated by the heavy losses suffered as a result of the German spring offensive in March 1918. The home army was stripped of all available personnel, leaving its ranks populated by under-aged, largely untrained recruits and low-category territorials, supported by part-time amateur auxiliaries recruited from men exempted from conscription, the medically unfit and the over-aged. Despite the military authorities' belief that it was militarily worthless, the Volunteer Force was partially mobilised and deployed to augment the coastal defences. The crisis passed in August, and by the following the month the invasion threat was downgraded to no more than a raid not exceeding 5,000 troops. The home defences were wound down, and the home army was rationalised as a training organisation dedicated to the provision of replacements to the front-line units overseas. After the war, home defence forces were demobilised with scant recognition given for their services. The Territorial Force was reconstituted as the Territorial Army and the Royal Defence Corps reappeared as the National Defence Corps, but the National Reserve and the Volunteer Force were not revived.
Background At the beginning of the 20th century, the British Army was a small, professional organisation designed to garrison the empire and maintain order at home.Mitchinson 2014 p. 11 It was augmented in its home duties by three part-time volunteer institutions, the militia, the Volunteer Force and the yeomanry. Battalions of the militia and Volunteer Force had been linked with regular army regiments since 1872. The militia was often used as a source of recruitment into the regular army. The terms of service for all three auxiliaries made service overseas voluntary.Chandler pp. 187–190Beckett 2008 pp. 13–16 At the turn of the century, the Second Boer War had revealed a number of deficiencies with British military planning. The army lacked sufficient manpower to cope with a major conflict overseas; the government was forced to reinforce it in South Africa by denuding the regular home defences and relying on auxiliaries to volunteer for foreign service. At one stage, regular forces available for the defence of the homeland comprised just nine cavalry regiments, six infantry battalions and three guards battalions. In February 1900, George Wyndham, Under-Secretary of State for War, conceded in Parliament that instead of augmenting the regular army's defence of the UK coast, the auxiliary forces were the main defence.Beckett 2011 pp. 200–205 There were doubts in both government and the military authorities about the auxiliaries' ability to meet such a challenge; the volunteers' performance in the war was questionable due to their poor standards of organisation, equipment and training.Beckett 2008 p. 27Beckett 2011 pp. 206–207Dennis p. 8
In 1903, the Committee of Imperial Defence (CID) estimated that to succeed, an invasion would require 70,000 troops, over 200 transport ships and a 48-hour embarkation time to succeed. It concluded that this would give the Royal Navy enough time to intercept the invasion fleet and allow the regular and auxiliary forces to man coastal defences.Mitchinson 2005 p. 3 Based on the CID's findings, the government adopted the 'blue water' strategy of home defence, in which the navy was the prime agent in defeating any large-scale invasion. The auxiliary forces, assisted by elements of the regular army, were given responsibility for defending against smaller-scale raids that might evade the navy. The bulk of the regular army was absolved from home defence duties, allowing it to focus on foreign commitments.Morgan-Owen p. 99
Territorial Force
A royal commission on auxiliary forces concluded in 1904 that they were not fit to defend the country unaided and that the only effective solution would be to introduce conscription.Beckett 2011 pp. 208–209 This option was regarded as political suicide by all parties and immediately rejected.Simkins p. 24Beckett 2011 pp. 208–209, 211 Efforts to reform both the regular army and the auxiliaries stalled in the face of political opposition until, in December 1905, a Liberal government took office, bringing in Richard Haldane as the Secretary of State for War.Beckett 2008 p. 28 His reforms created a regular army expeditionary force of one cavalry and six infantry divisions. To reinforce the army in times of crisis, the militia was converted into the Special Reserve and the Extra Reserve, comprising volunteers who would undergo military training in their civilian lives. The Volunteer Force and yeomanry were amalgamated to form the Territorial Force with an establishment of over 300,000 men.Chandler p. 204Beckett 2011 pp. 216–217Mitchinson 2005 pp. 5, 6
Haldane's purpose in establishing the Territorial Force was to create the means by which the regular army could be expanded in a major conflict overseas. The force was better organised and integrated than the previous auxiliaries. It was organised into 14 infantry divisions and 14 mounted brigades, structured along regular army lines with integral supporting arms of artillery, engineers and signals, along with supply, medical and veterinary services. Having designed what was in effect a second line to the regular expeditionary force, Haldane was forced to compromise by opposition from the existing auxiliaries to a liability for foreign service. Although he still hoped the Territorial Force would be the primary means of expanding the army in a major war overseas, at its creation on 1 April 1908 he was forced to present it as a primarily home defence force. Territorials could not be compelled to serve outside of the United Kingdom, though Haldane hoped they would volunteer for foreign service on mobilisation. In 1910, the Imperial Service Obligation was introduced to allow them to volunteer in advance.Simkins pp. 16–18Beckett 2011 pp. 215, 217Dennis pp. 13–14, 19 The force was financed, trained and commanded centrally by the War Office but raised, supplied and administered by local County Territorial Associations.Beckett 2008 pp. 30, 43–44
Invasion threat and conscription debate
A second CID study in 1908 reiterated the belief that an invasion would be defeated before it made landfall, rendering a large home army unnecessary in the eyes of the military authorities. The War Office considered two regular divisions and 40,000 auxiliaries would be enough to defeat any force that did manage to reach the nation's shores.Mitchinson 2005 p. 7 The military authorities begrudged the money spent on what they perceived to be an inefficient amateur auxiliary and believed it could have been better spent on the regular army. The relationship between the County Territorial Associations and the War Office was often difficult. The associations frequently complained about excessive bureaucracy and the inadequate finance with which they were expected to forge a force capable of defeating an invasion.Mitchinson 2008 pp. 13–16, 105 Because they believed the Territorial Force was of questionable utility, the military authorities prioritised expenditure on the regular army, leaving the force armed with obsolete weapons.