Duncan enlisted on 25th September 1909. He was 22 years and 4 months old; and was a labourer by trade, and was living at 69 Shiprow, Aberdeen, Scotland. At the outbreak of war he was stationed with No 13 Coy, and was mobilized to serve abroad with the 19th Field Ambulance. He entered the war in France, with the unit, on 21st August 1914.
Whilst serving with the 1st Division Field Ambulances, on 24th May 1915, orders were given that when shelling commenced NCO’s & men in billets were to go down into lower rooms and where possible into cellars. Shelling commenced around 8.35 p.m. on the 24th, with the first shell striking the hospital, hitting the brickwork by the side of the front entrance of A Block, at the junction of tiled pavement and wall, making a hole about 2 feet in diameter & 1 ft deep. Some of the men whose duty it was to upload incoming ambulance cares were around this door and a few others were in the vicinity. Though the hole made was small, the explosive effect was considerable, with the shell splintering into small fragments and as a result wounding some of the men.. Duncan was one of them, sustaining severe shell wounds to his legs, chest and chin. He was evacuated back to the UK on 30th May, then after recovering was posted to Malta, serving with No 2 Malta Coy. His service time was due to expire on 29th September 1916 but he signed up again for the duration of the war. He returned to the UK on 13th March 1919, then was posted to Army Reserve on 29th April. He was discharged from the service on 31st August 1920.
He was the husband of Margaret Davidson Cameron - married on 13th August 1908.