Under the pre-war British Army system, created during the Haldane Reforms, each regiment, in addition to having two regular battalions would have two reserve formations associated with it. One would be special reserve battalion, while the other would be the Territorial Force units. In the case of the Wiltshire Regiment, the 3rd Battalion was the special reserve formation. The 3rd Wilts came into active service during 1914. It would remain in the home islands throughout the war. For most of the war, it would act as the depot and training unit for the battalions of the Wiltshire Regiment. In 1917, it moved from the depot at Devizes to join the Portland Garrison in 1915. In 1917, the 3rd Wiltshires would be transferred to the Thames and Medway garrison.