He was a capable soldier rising through the ranks to Lance Corporal and then to Sergeant.

His first service overseas was to Egypt on 21 September 1915.

On 18 June 1917 the award of a MSM was announced in the London Gazette for devotion to duty in Salonika during 1915 and 1916.

On 29 January 1918 Sgt Chapman was transferred to the 2nd Essex regiment as a Temporary 2nd Lieutenant.

On 2 September 1918 at Drocourt-Queant he was involved in an action that would lead to the award of a Military Cross which was announced in February 1919.

The citation read  For conspicuous gallantry and devotion to duty in an attack on Drocourt-Queant line on September 2nd 1918. He took command after his company commander had been killed and cleared the way by rushing a machine-gun post single handed, reorganising his men on the line of the objective under difficult conditions. The same night he got his company out of their positions and re-organised them at right angles in readiness for another assault. He showed great skill in carrying this out in darkness and under heavy gas shelling.