 He received his first commission in regular army on 20 November 1875, as a lieutenant in the 102nd Foot, and then joined the 2nd Regiment of Foot (Queen's Royal Regiment (West Surrey)) on 18 December 1875.Promotion to captain followed on 15 February 1886.From 1888, Hacket Pain served in the Sudan during the Mahdist War as a captain in the West Surreys.