Sydney John Mann commenced service on 14 June 1915. He served in Egypt and on the Western Front. In addition to his campaign medals Private Mann was awarded the French Medaille d’Honneur. He received his final discharge on 6 June 1919, having served for a total of three years and 359 days.

Citation for Medaille d'Honneur: Medaille d'Honneur avec glaives (en Argent) : LG 17 March [April?] 1920, p3406 " For Distinguished services rendered in connection with the war."; Conferred on Pte Mann by the President of the French Republic and Royal Permission for its Acceptance appeared in the London Gazette dated 16 March 1920. The medal was presented to him at Napier on 18 October 1921.

According to his family Sydney J Mann was an ambulance driver. “Sydney John Mann who was my mother's father, he was a private and indeed drove an ambulance in the NZEF and was a sergeant in the home guard at Napier during the second war. I understand he returned from the first war late having served in France and Belgium for the War Graves Commission and hence the citation from the French Government. On his return his demob photograph oddly has him in full uniform but holding a large vase - reputedly because he could not stop his hands from shaking - he never discussed his experiences while away and died in 1951.” (family correspondence)