1913 William Leslie Green joined the Territorial Force in 1913 at the age of 18. This postcard sent to his father in late 1913 shows a group of NCOs at a Territorial Force training camp. A non-commissioned officer (NCO) is a member of the armed forces who has achieved the rank of officer by rising from the lower ranks rather than by receiving a commission. The Territorial Force was an army of volunteers which supported the British Army. Volunteer units have existed for centuries, but in 1908 they were merged to form the Territorial Force. Members of the Territorial Force were mobilised in the First World War and served alongside the regular army. In 1920 the Territorial Force units were formed into the Territorial Army. The Territorial Army was mobilised again in the Second World War.