Per his military service record (regimental no. 4732), Sidney Bennett was born at Paddington, Sydney. He gave his age as 24 years and 10 months, his marital status as single, and his occupation as labourer. His description on his medical was height 5 feet 9 ½ inches tall, weight 11 stone 5 lbs., with a dark complexion, blue eyes, and dark hair. His religious denomination was Roman Catholic. He completed his medical on the 8th October 1915 at Gilgandra and was attested by Captain Nicholas on the 9th October 1915 at Gilgandra. He claimed to have had no previous military service.
On his embarkation roll his address as time of enrolment was Hornsey, David Street, North Sydney, N.S.W., and his next of kin is listed as father, Mr H. Bennett, Hornsey, David Street, North Sydney, N.S.W.
After completing the march he went to Liverpool Camp as reinforcement for the 13th Battalion.
Private Bennett departed Sydney on the HMAT A15 Star of England on the 8th March 1916. On the 19th of April 1916 he transferred to the 45th Battalion in Egypt.
On the 2nd June 1916 Private Bennett left Alexandria aboard the Kinfauns Castle bound for France, arriving at Marseilles on the 8th June 1916.
On the 22nd September 1916 he received a gunshot wound to his left forearm whilst conducting a working party near Vierstraat, Belgium. He was hospitalised and evacuated to England.
On the 13th September 1918 he was transferred to the 54th Battalion, and on the 11th October 1918 to the 56th Battalion.
Private Bennett commenced his return to Australia on the HT Devanha on 8th May 1919, arriving in Australia on the 19th June 1919. He was discharged on the 10th August 1919.