The origins of a British heavy "siege" howitzer lie in advances in technology and the 21 cm howitzers used by the German field army. UK had purchased
Skoda 9.45-inch howitzers from Austria in 1900 for service in South Africa. A practice camp in the 1900s showed this howitzer's high minimum elevation was a major problem. In due course Britain decided to develop its own heavy weapon, but retained the Skoda transport technique of moving it in three loads on wheeled trailers (either horse- or tractor-towed). A trial gun was received in 1913 and fired at
Woolwich and
Shoeburyness during the winter. In July 1914 it was sent to the tactical firing range at
Rhayader with a siege company. The assessment was "This equipment is a vast improvement on any other in use in the siege artillery, and is worth taking with an army." Major General
von Donop, Master-General of the Ordnance, immediately ordered 16 guns and a further 16 were ordered in October 1914. The prototype gun, "Mother", was in action in France on 31 October 1914 and production guns entered service in 1915. and hydraulic buffer. The initial design suffered from excessive recoil and was modified in 1916. In 1917 the recoil was further improved by addition of a recoil indicator and cut-off gear. Full recoil (40-inch Mk I, 44-inch Mk II) was allowed at lower elevation, hence absorbing most of the horizontal (i.e. backward) force. A shorter recoil (23-inch Mk I, 20-inch Mk II) was allowed at high elevation where the ground itself could absorb much of the vertical (i.e. downward) recoil force. This prevented the breech from hitting the platform. The barrel had to be depressed 3° for loading, as can be seen in the photograph, shown below, of a howitzer of the Australian 55th Siege Battery.
Mark II The Mk I's range was relatively limited and in June 1916 the senior Artillery commander in France,
Major General Birch, requested among other artillery improvements an increase in range to
"even if an increase of the weight of the equipment is entailed". This resulted in the Mark II gun in December 1916, with a heavier maximum propellant charge, a longer barrel and an increased range of . Combat experience showed the higher-velocity Mk II barrel had a reduced life, estimated at 3,500 rounds, compared to 6,000 rounds for the Mk I. ==Combat use==