The requirement or more of a request from the Army was to create something with the similar capability of the well performing 305mm howitzer but in a smaller version so it could be transported in a single load instead of a multi-trailer car-train. This was required as in 1914-1915 the frontline was moving back and forth fairly often so setting up a siege artillery on a short notice was a decisive factor in a battle. And regardless how effective the 305mm was, it took almost a day to bring it into a condition of firing once it was transported to the required location. And i would like to emphasize on the transporting part here. In the early part of the century paved roads outside of the cities were not that common and most of the transport happened over the rail network, however the frontline did not follow the railway so dragging through a 20 tons 3 trailer train through mud and dirt for miles was not an easy or a quick job…
The 21 cm Mörser M. 16 was a heavy howitzer used by Austria-Hungary during World War I and built by Škoda Works in Pilzen. The design began in 1915 for a wheeled howitzer that could be towed in a single load by a tractor as per the request of the leadership of the Army. The first prototype was not up to the requested specs as it was too heavy and traversing was difficult due to the very high limber bar pressure. Skoda got back to the drawing board and redesigned the trailers and mount. Few years later a second howitzer was delivered in mid-1917 however this broke down into two loads for transport. This, at least solved the traversing problem of the first weapon, as reported by the test battery assigned to the 11th Army, but as it had two trailers instead of one, the mobility of the howitzer paid the price. In the meantime, a third prototype had been ordered as the M. 18 with a carriage based on that of the Škoda 305 mm Model 1911 that would allow for full traverse but due to this more time needed to emplace the firing platform. This version broke down into three loads for transport. As the manufacturing of this howitzer was time-consuming, no M.18s were delivered by the end of the war.
In the mid-war period Skoda built some modified versions as the M. 18/19 for the newly independent Czechoslovakian Army, where they were known as the 21 cm Moždíř vz. 18. After the Occupation of Czechoslovakia in 1939 the Germans adopted them under the names of 21 cm Mörser 18/19(t) or kurze 21 cm Mörser(t) and used at least 15 on coast-defense duties in Norway.
