The Ordnance QF 18-pounder, or simply 18-pounder gun, was the standard British Empire field gun of the First World War-era. It formed the backbone of the Royal Field Artillery during the war, and was produced in large numbers. It was used by British Forces in all the main theatres, and by British troops in Russia in 1919. Its calibre (84 mm) and shell weight were greater than those of the equivalent field guns in French (75 mm) and German (77 mm) service. It was generally horse drawn until mechanisation in the 1930s.