The Special Reserve was formed from the Militia in 1907 and, in the Dorset Regiment, became the 3rd (Special Reserve) Battalion.
The 3rd Dorsets mobilised on 5th August 1914 at the Depot in Dorchester under the command of Lieutenant-Colonel Castleman-Smith. On the same day 300 regular reservists left for Belfast to join the 1st Battalion before they left for France as part of the British Expeditionary Force. The number of volunteers swelled from only 400 to over a 1000 and equipping, feeding and clothing them all posed a logistical challenge. On 9th August the Battalion marched to billets in Wyke Regis, where conditions initially were sparse. The 3rd’s first wartime role was guarding the railways, waterworks and other sites of strategic importance. Quickly, however, its prime purpose became equipping and training men who would be drafted to the Regiment’s battalion’s in the various theatres of war.
By September 1914 all of the regular reservists had been despatched to the Front as reinforcements and the ‘Special Reservists’ followed immediately afterwards. Before the end of the year men were being sent out whose total service was three months of training. (This contrasted with the men of the 5th and 6th Service Battalions, who received at least 6 months’ training. Over time the training developed on specialist lines and extra companies were formed to include men who had returned from the Front and for those considered medically unfit for active service.
By the end of 1915, over 100 officers and 6,000 men had already passed through Wyke Regis as reinforcements for the Dorsets and other regiments. The service number of many soldiers of the Dorsetshire Regiment who fought during the war were prefixed by a 3/….., which denoted that at some time they had been attached to the 3rd Battalion.
During the five years the 3rd Dorset spent at Wyke Regis other drafts of men passed through the camp under training including Dragoon Guards and a detachment of the ‘Non Combatant Corps’, who were conscientious objectors.
In 1919, the 3rd Battalion were moved to Portsmouth, leaving a small detachment at Wyke Regis, before leaving for Londonderry and taking over all ranks of the 4th Battalion. Later that year the 1st Battalion arrived in Ireland and replaced the 3rd, which was demobilized for ever.