Born in Sebastopol, Victoria and a Moulder by trade, Jack Cairns was 18 years and single when enlisted on the 17th of December 1917 in the 7th General (Victorian) Reinforcements, Australian Imperial Force, with the rank of Private, Number 55576. His Unit embarked from Melbourne, Victoria, on board HMAT A74 'Marathon' on the 23rd of July 1918. Allotted to the 7th Battalion on the 27th of September 1918 and marched in the 1st training Battalion from Australian 7th General Service Reinforcements; on the 18th of December 1918 transferred from the 7th Battalion; on the 24th of November 1918 marched into A.G.B.D. (Australian General Base Depot) FROM England ex General Service Reinforcements; on the 6th of April 1919 transferred to 4th Divisional train from Vet Hospital and taken on strength of 4th Divisional Train from Vet Hospital. Admitted to Hospital for Scabies on the 20th of September 1919 and discharged to duty on the 26th of September 1919. Embarked for return to Australia per 'Barambah' on the 3rd of September 1919 and disembarked on the 25th of October 1914. Discharged on the 9th of November 1919 with the Termination of Period of Enlistment. Tree No. 3545