Denis Sidney Cass enlisted on the 13th of September 1915 in the 15th Battalion, 14th Reinforcement, Australian Imperial Force, with the rank of Private, Number 4469. His Unit embarked from Brisbane, Queensland, on board HMAT A62 'Wandilla' on the 31st of January 1916. Admitted to 4th Auxiliary Hospital, Abbassia – Mumps on the 26th of March 1916; admitted to Hospital, Shoubra – Enteric; admitted to no 4 Auxiliary Hospital, Abbassia; on the 21st of May 1916 transferred to Ras-el-Tin, Alexandria, Enteric; on the 10th of July 1916 transferred to 1st Australian Dermatological Hospital, Abbassia. Embarked at Alexandria for overseas to join British Expeditionary Force; wounded in action on the 2nd of February 1917 gunshot wound Knee; on the 19th of October 1917 wounded in action (Gas) 2nd occasion; on the 11th of January 1918 admitted to Military Hospital, Fovant – Influenza; on the 5th of March 1918 admitted sick to Brigade Hospital – Influenza. Embarked for return to Australia per H.T. 'Canberra'on the 23rd of July 1919 and Disembarked at Sydney on the 14th of September 1919. Discharged from the A.I.F. at Brisbane – medically unfit. Tree No. 2783