Henry enlisted into the R.A.M.C., Special Reserve on 31st October 1914. He was 20 years and 30 days old; was a Painter by trade; and was living at 7 Whitefriars Street, Dublin at the time. He served with 14th Coy in Dublin until he was transferred to the training centre, New Army at Limerick. He entered the war in Egypt on 31st March 1915. Henry was serving with No 17 General Hospital in Alexandra, when he was struck off the strength of the unit on 16th April 1915, having been transferred to serve on the Hospital Ship “Gascon”. On 6th April 1916 he embarked at Southampton and sailed to Rouen, France, where he disembarked on the 6th. He was then posted to serve with the 5th Field Ambulance, joining them in the field on 12th April 1916. On 28th July 1916 he was wounded in action and admitted into No 5 Casualty Clearing Station suffering with shell shock. He was then evacuated back to No 14 Stationary Hospital, Boulogne, where he remained until 7th August 1916 when he was admitted into No 1 Convalescent Depot. On 10th August he joined Base Details in Rouen, who posted him to serve with the 8th Field Ambulance, joining them in the field on the 28th August 1916. On 18th June 1917 he was again wounded in action, suffering from the effects of gas but returned to duty the next day, on 19th June 1917. On 18th July 1917 he was posted for temporary duty attached to No 42 Bde, R.F.A., rejoining his unit on 7th August 1917. On 12th August he was transferred to serve with the 2nd Field Ambulance but was awarded 14 days field punishment for overstaying his leave to the UK by 3 days, and was subsequently transferred to the 141st Field Ambulance, joining them in the field on 22nd November 1917. On 5th February 1918 he was admitted ‘sick’ into the hospital of this unit. He was discharged from hospital of No 8 Field Ambulance on 20th February 1918 and rejoined his unit for duty. He was admitted ‘sick’ into the hospital of his unit again on 10th September 1918. This time he was evacuated to No 23 Casualty Clearing Station, who evacuated him back to No 4 General Hospital via No 38 Ambulance Train. On 20th October 1918 he was posted to serve with No 4 Stationary Hospital, where he stayed until he proceeded to England for demobilization on 8th May 1919. He was discharged on termination of period of engagement on 30th October 1919.