Line infantry
In accordance with the Territorial and Reserve Forces Act 1907 ("7 Edw. 7, c.9") which brought the Territorial Force into being, the TF was intended to be a home defence force for service during wartime and members could not be compelled to serve outside the country. However, on the outbreak of war on 4 August 1914, many members volunteered for Imperial Service. Therefore, TF units were split into 1st Line (liable for overseas service) and 2nd Line (home service for those unable or unwilling to serve overseas) units. 2nd Line units performed the home defence role, although in fact most of these were also posted abroad in due course. Later, a 3rd Line was formed to act as a reserve, providing trained replacements for the 1st and 2nd Line units. Similarly, by 1915 most 2nd Line infantry battalions were formed into 2nd Line brigades and divisions with the same title and composition as the pre-war 1st Line formations.