Magic lantern slide WW1, 1914-1918, World war one images. A 21cm Morser 16, a form of heavy howitzer type artillery used by the Germans during the Great War. They actually classified it as a mortar but it had a rifled barrel and was breech loaded. You may remember it as the gun featured in the film 'war horse. Display of captured German weapons and artillary at Horse Guards Parade, London 3rd November 1915.