The outbreak of war created an immediate demand for reinforcements to bolster the small, heavily outnumbered British Expeditionary Force. On 7th August 1914 (on the eve of their departure for France) the 1st Dorsets were ordered to send three officers and fifteen NCOs to Dorchester to form the nucleus for a new ‘Service’ Battalion. Three days later recruiting for the new Battalion began under the command of Major C. C. Hannay, then commanding the Regimental Depot.
Responding to Kitchener’s call for volunteers for a New Army, recruits flooded into Dorchester, the vast majority being Dorset men. On 28th August the newly raised Service Battalion went to Belton Park, Grantham, to begin training as part of the 11th (Northern) Division. After six months training, they moved to Witley Camp near Hindhead and joined 34 Brigade, which was destined for Gallipoli.
On 11th July 1915 the 5th landed at Suvla Bay on the Gallipoli peninsular. In the next six months they lost relatively lightly in battle but heavily from the sickness that was the scourge of soldiers in this abortive campaign. In September sixty men were admitted to hospital with sickness. In three weeks from mid-October the figure was 150. Evacuated in January 1916, the Battalion redeployed to Egypt, where they remained for six months digging defences against an expected Turkish offensive which never came.
In July 1916 the 5th were sent to France, joining VI Corps in the Third Army. Although the Somme offensive had begun on 1st July, the Battalion first went into the line in the quieter sector south of Arras. In September, the Battalion moved south, to just below Thiepval at Mouquet Farm. Theirs was a bloody introduction to the Somme. The farm was partly held by the Germans, huge numbers of whom occupied a vast dugout below it. In this and in the attack that followed, two thirds of the 5th were killed or wounded. In the freezing winter of 1916/17 they lost heavily again in an attack near Beaucourt.
May and June 1917 saw the 5th Dorsets in action at Messines. On 16th August, now near Ypres, they launched a very successful attack near Langemarck from which they emerged with – by the standards of the time – the relatively light casualties of thirty killed and 120 wounded. In early October they lost more heavily attacking Poelcapelle in the horrific closing phase of the Third Battle of Ypres which is remembered as Passchendaele.
After ten months holding the Loos salient further south, in late September and October 1918 the 5th Dorsets played a part in the final rapid advances that led to the Armistice. They achieved particular success in a fiercely opposed attack north-west of Cambrai, which cost relatively few lives although enemy shelling killed their Colonel, Padre and Medical Officer.
On 11th November 1918 the Battalion were out of the line when news of the Armistice reached them. After a short spell in Belgium they returned to Dorchester, where they were disbanded.