Associated with the service of Captain Henry Garnet Forrest. Forrest was born in Brunswick, Melbourne in December 1895 and was a clerk on enlistment in the 23rd Infantry Battalion on 19 February 1915. 123 Company Quartermaster Sergeant Forrest embarked for overseas service aboard HMAT Euripides on 10 May. After spending time in Egypt, he landed at Gallipoli with the 23rd Battalion on the night of 4 to 5 September.
Back in Egypt after the Gallipoli campaign, Forrest was taken on strength by 46 Battalion and promoted to second lieutenant on 12 March 1916. He proceeded overseas to France on 2 June, where he remained until the following year. Forrest was awarded the Italy Silver Medal for Military Valour in 1917, for leading a successful raid into enemy trenches at the Hollandscheschuur Salient in September 1916. He was also mentioned in despatches.
Forrest transferred to the Australian Flying Corps in April 1917, and was one of the first Australian pilots to be sent to France during the Ypres campaign. There he took part in operations with 43 and 32 Squadrons, Royal Flying Corps (RFC). Forrest was wounded on 6 August 1917 and transferred back to England. In November 1917 he was posted to 68 Sqn (Aust) RFC (titled 2 Squadron, Australian Flying Corps from 19 January 1918) and was promoted to Captain on 22 February 1918.
Forrest claimed eleven victories, operating as a flight commander with 2 Sqn and was awarded the Distinguished Flying Cross on 2 July. His citation reads: 'His leadership of patrols has been characterised by great dash and determination, whether on high or low work. He has displayed skill in manoeuvring and boldness in attacking superior numbers.'
Forrest joined the Home Establishment in July 1918, where air and ground crews were trained, and squadrons were prepared for service in France. He was admitted to Cobham Hall sick on 5 September. He was invalided back to Australia aboard HT Marathon on 6 November 1918 arriving in Melbourne on 1 January 1919. Forrest's appointment in the AIF was terminated on 23 February 1919.