Forsyth moved to Melbourne, where he served as a staff officer. He became secretary to the inspector general, Major General Finn, from 13 November 1905 to 1 October 1906. He joined the Victorian Instructional Staff on 1 February 1907 and was promoted to major on 28 May 1908. In 1909–1910 he was posted to India on exchange duty with the British Indian Army as brigade major of the Amballa Cavalry Brigade. Returning to Melbourne, he was deputy assistant adjutant general (DAAG) for instruction from 1 to 31 December 1910. Forsyth was a GSO2 at Army Headquarters from 1 November 1911 to 30 June 1912, became director of equipment on 1 July 1907, and was promoted to lieutenant colonel on 1 March 1914. On 1 August 1914, he became quartermaster general and a member of the Military Board.