In September 1939, on the outbreak of the Second World War, the Dorset Regiment had two Regular battalions and two battalions of Territorials (part-time volunteers), one of which was new and in the process of forming. These – the 1st, 2nd, 4th and 5th Battalions – were the four battalions that fought as Dorsets. During the war other battalions were formed. The 6th(Home Defence), 9th and 70th (Young Soldiers) Battalions remained in the UK. The 30th served overseas as garrison troops but never fought. The 7th and 8th Battalions converted to become light ant-aircraft regiments in the Royal Artillery and fought as gunners in North Africa, Italy and North West Europe.
The four battalions that fought as Dorsets saw service in France in 1940, on Malta and in Sicily, Italy, Burma and North West Europe. Members of the Regiment also fought with other units in other theatres including North Africa, Greece, Singapore and Madagascar. Many Dorsets came from the county but many did not. Some were Regular soldiers, some Territorials. Most were wartime volunteers and conscripts. 1,170 of them were killed, more than 3,000 wounded and more than 500 taken prisoner. In five years fighting they won 25 new battle honours for the Regiment and some 500 awards for gallantry, adding new chapters to the already proud history of a fine county regiment.