William enlisted into the R.A.M.C., Territorial Force, Eastern Mounted Brigade Field Ambulance on 6th February 1912. He was serving with the 9th Cavalry Field Ambulance when the unit was marching with the Brigade on 11th August 1918 at Sur-La-Luce. The unit transport was bombed and the men were caught in an exploding ammunition dump. Ernest was wounded at the time. He was discharged from the army on 16th January 1919 as no longer fit and received a Silver War Badge. In both the Medal Index Cards and the unit war diary, William is referred to as William Steinson.