Territorial Force The Territorial Force ( TF ) was the volunteer reserve component of the British Army from 1908 to 1920 , when it became the Territorial Army . The Territorial Force was formed by the Secretary of State for War , Richard Burdon Haldane , following the enactment of the Territorial and Reserve Forces Act 1907 ( 7 Edw . 7 , c . 9 ) , which combined and re - organised the old Volunteer Army with the Yeomanry . The TF was formed on 1 April 1908 . As part of the same process , remaining units of militia were renamed Special Reserve . The TF was envisaged as a home defence force for service during wartime ; units were liable to serve anywhere within the United Kingdom when the force was embodied , but could not be compelled to serve outside the country . However , any member or unit of the force could volunteer to be liable for overseas service - in 1910 , when asked to nominate for Imperial Service overseas in the event of mobilisation , less than 10 % of the Force chose to do so . Individual members could also choose to be liable to be called up for service within the United Kingdom even in situations when the force as a whole was not embodied . Structure . On formation , the TF contained 14 infantry division s , and 14 mounted yeomanry brigades . The individual units that made up each division or brigade were administered by County Associations , with the county ' s lord lieutenant as president . The other members of the association consisted of " military members " ( chosen from the commanding officers of the units ) , " representative members " ( nominated by the county council s and county borough s in the lieutenancy county ) and " co - opted members " ( often retired military officers ) . Associations took over any property vested in the volunteers or yeomanry under their administration . The basic building block was the yeomanry regiment or infantry battalion ; these numbered 54 regiments of yeomanry , and 207 battalions of territorial infantry . In addition , there were 23 volunteer batteries of the Royal Garrison Artillery , 151 of the Royal Field Artillery , and 14 of the Royal Horse Artillery , as well as volunteer engineer , medical and supply companies . Each regiment or battalion had a regular army officer attached as full - time adjutant . Every Territorial battalion of infantry was attached to a regular Army regiment ; for example , the Royal Scots had two regular battalions , a reserve battalion , and seven Territorial battalions numbered the 4th through 10th . The original divisions of the Territorial Army were : The original mounted brigades were : Service . In August 1914 , after the outbreak of World War I , Territorial units were given the option of serving in France and , by 25 August , in excess of 70 battalion s had volunteered . This question over the availability of Territorial formations for overseas service was one of Lord Kitchener ' s original motivations for raising the New Army separately . A second line of Territorial units were raised by the respective County Associations in August and September 1914 . As a result , the first - line battalions were renamed so that the 5th Battalion of the East Surrey Regiment became the 1 / 5th Battalion , and the second - line duplicate became the 2 / 5th Battalion . In many cases , a third - line battalion ( the 3 / 5th ) was formed after the first - line battalion was sent overseas , freeing up the second for foreign service ; the third - line battalions were usually used for home defence or training ; few saw action . As the second line of battalions were organised for foreign service , a set of second - line divisions was formed , again prefixed with " 2 " to distinguish them - for instance , the second line ' Wessex Division ' was originally called the ' 2nd Wessex Division ' . However , many of these were quickly renumbered ; divisions were assigned numbers in April 1915 and the 2nd Wessex became the 45th Division . The second line Territorial Force divisions were : By the end of the war , 692 Territorial Force battalions had been raised . In total , nine second line divisions were raised . No complete divisions of third line battalions were raised . Also considered divisions of the Territorial Force were : Territorial units initially saw service in Egypt , India and other Empire garrisons such as Gibraltar , thereby releasing regular units for service in France and enabling the formation of an additional five regular army divisions ( for a total of eleven ) by early 1915 . The first Territorial division to join the fighting on the Western Front was the 46th Division in March 1915 . The 42nd and 52nd divisions were sent to Gallipoli as reinforcements for the Helles front in May and June 1915 . As the war progressed , and casualties mounted , the distinctive character of Territorial units was diluted by the inclusion of conscript and New Army drafts . Following the Armistice , all units of the Territorial Force were gradually disembodied .