The 21 cm Mörser M. 16 was a heavy howitzer used by Austria-Hungary during World War I. Skoda began design in 1915 for a wheeled howitzer that could be towed in a single load by a tractor. The first prototype wasn't satisfactory as it was too heavy and traversing was difficult due to the very high limber bar pressure. A second howitzer was delivered in mid-1917 that broke down into two loads for transport. This, at least, cured the traversing problem of the first weapon, as reported by the test battery assigned to the 11th Army. In the meantime, however, a third prototype had been ordered as the M. 18 with a carriage based on that of the 30.5 cm Mörser M. 16 that would allow for full traverse at the price of more time needed to emplace the firing platform. It broke down into three loads fo