Following the success of their BL 9.2-inch howitzer, Vickers designed an almost identical version scaled up to a calibre of 12 inches, the Mk II entering service on the Western Front in August 1916.[2] Eight complete equipments are reported as arriving in August 1916 and being in action in France shortly afterwards.
The 12-inch was dismantled and transported in six loads mounted on traction engine wheels. It was then reassembled on its static siege mounting on top of a steel holdfast, with 22 tons of earth in a box sitting on the front of the holdfast in front of the gun, to counteract the kick of firing.
^Mk II = Mark 2, Mk IV = Mark 4. Britain used Roman numerals to denote Marks (i.e. models) of ordnance until after World War II. Hence this article describes the second and fourth models of British BL 12-inch howizers. Marks I, III and V were the models of the unrelated BL 12-inch railway howitzer.