Henry John Matson was just a boy when he enlisted on 3 July, 1917. He was only eighteen years and two months old, and had to get a document of consent from his mother. His father, also Henry Matson, was already at the war as part of the 21st Battalion of the A.I.F., although he was not an Australian citizen, having been born in Finland and  declaring himself a Russian citizen. He was to die in France in October, 1918, from a gastric carcinoma. His mother, Christine. lived in Berkley St., Carlton.Young Henry had been born in Echuca, Victoria, and at the time of enlisting, gave his occupation as grocer.

He was sent to Broadmeadows for training, then to Sydney to embark. leaving on the Orontes on 5 June, 1918 and disembarking at Liverpool, England, on 11 August. He had suffered an infected foot on the voyage over and had to be treated in the ship's hospital for a day.

Along with the other recruits, he marched in to join the 9th Training Battalion, then on 6 November, 1918, sailed from Southampton to Fovant and was taken on strength in the field with the 39th Battalion at Rouelles on 9 November, two days before the armistice. Five days later, he caught influenza and was sent to hospital for six days, before being discharged to duty on 12 November, 1918.  He marched out to his unit on 21 November. Nothing in his record indicates where they were, but presumably, he assisted in troop evacuations back to Britain and was listed as part of the 3rd Reinforcements General Service Group. On 8 May, 1919, he marched into Le Havre, then on to England, marching out to Codford. From there he was returned to Australia and discharged from further service on 5 December 1919.