The Territorial Force was created in response to the need for a more adaptable and responsive military system in Great Britain, particularly after the experiences of the Second Boer War (1899-1902). Soldiers from the regular army often became overstretched during conflicts, exposing a lack of immediate local defense capacities. As a result, the government sought to structure a volunteer reserve that would enable citizens to serve part-time, balancing military readiness with civilian life. This was part of the 1907 Haldane Reforms led by then-Minister of War Richard Haldane, which revolutionized the British military structure.

The establishment of the Territorial Force allowed for local regiments to be created, enabling manpower to be mobilized quickly in times of crisis. Individuals would receive military training and maintain their civilian careers, responding to a growing sentiment that regular armies could not sustain prolonged engagements without local support. The Territorial Force encompassed various units throughout the country, marked by a distinct aim to integrate community involvement in national defense.

In 1920, the Territorial Force was renamed the Territorial Army, which reflects its long-lasting legacy. The concept of a volunteer reserve component was further solidified with the development of the Army Reserve, which emphasized the importance of retaining trained soldiers who could augment regular forces when necessary. The Territorial Force ultimately laid the groundwork for modern reserve forces in the UK, showcasing the balance between military obligation and civilian commitment.