Gamble was first commissioned (brevet) as an ensign in the 4th Foot Regiment in 1844 and then as a Lieutenant was posted at ‘Maker Barracks’ Vaulters Home Maker, St Germans in Cornwall where he passed his exam in native languages (on 26 January 1847) and worked to become Captain and to serve in Turkey between 1854 and 1855, and was with the 4th Regiment in the Crimean Campaign in 1855, after which he was decorated (receiving a medal with clasp, and the Turkish medal in 1856) and promoted to the rank of Major.