Skoda 305 mm Model 1911 The Škoda 30 . 5 cm Mörser M . 11 was a siege howitzer produced by Škoda Works and used by the Austro - Hungarian Army during World War I and by Nazi Germany in World War II . Development . Development began in 1906 , when a development contract was placed by the Austro - Hungarian high command with Skoda - Werke in Pilsen to develop a weapon capable of penetrating the concrete fortresses being built in Belgium and Italy . Development work continued until 1909 , when the first prototype was finished and , in 1910 , fired secretly in Hungary . The weapon was able to penetrate of reinforced concrete with its special armour piercing shell , which weighed . There were a few technical problems with the first piece , but , after few reconstructions in 1911 , the upgraded piece made another round of testing in Felixdorf and in the mountains of Tyrol . After that , Moritz von Auffenberg , the Minister of War , placed an order for 24 of the new weapons . Description . The weapon was transported in three sections by a 100 - horsepower 15 ton Austro - Daimler road tractor M . 12 . It broke down into barrel , carriage and firing platform loads , each of which had its own trailer . It could be assembled and readied to fire in around 50 minutes . The mortar could fire two types of shell , a heavy armour piercing shell with a delayed action fuse weighing 384 kg , and a lighter 287 kg shell fitted with an impact fuze . The light shell was capable of creating a crater 8 meters wide and 8 meters deep , as well as killing exposed infantry up to away . The weapon required a crew of 15 - 17 , and could fire 10 to 12 rounds an hour . After firing , it automatically returned to the horizontal loading position . In 1916 , the M . 11 design was upgraded and the new M . 11 / 16 was produced - the difference was mainly that the firing platform had been modified to allow for a traverse of 360 degrees . Also in 1916 , a new model was released , the M . 16 , which had longer barrel ( L / 12 ) and longer range . History . Eight Mörsers were loaned to the German Army and they were first fired in action on the Western Front at the start of World War I . They were used in concert with the Krupp 42 cm howitzer ( " Big Bertha " ) to destroy the rings of Belgian fortresses around Liege ( Fortified Position of Liège ) , Namur ( Fortified Position of Namur ) and Antwerp ( Forts Koningshooikt , Kessel and Broechem ) . While the weapon was used on the Eastern , Italian and Serbian fronts until the end of the war , it was only used on the Western front at the beginning of the war . In 1915 , ten howitzers were used in support of the Austro - Hungarian - German invasion of Serbia under the German General August von Mackensen . One of these is restored in Belgrade Military Museum . By the end of the war , 79 of the weapons of all three types were in service . Only 24 were destroyed . In the period between the world wars , large numbers of mortars were in service in Yugoslavia ( 4 M . 11 and 6 M . 16 ) , Romania , Italy ( 23 M . 11 , 16 M . 11 / 16 and 16 M . 16 ) , Czechoslovakia ( 17 M . 16 ) and Hungary ( 3 M . 11 and 2 M . 16 ) . There were only two in Austria ; one in the Arsenal , Army Museum in Vienna , the second as a training weapon in Innsbruck . In 1939 , Germany seized all 17 pieces from Czechoslovakia and repaired the howitzer from the Arsenal Museum , designating them " 30 . 5 cm Mörser ( t ) " . In 1941 , they obtained five more weapons after the defeat of Yugoslavia and placed them into service as the " 30 . 5 cm Mörser 638 ( j ) " . They saw service against Poland , France and the Soviet Union in World War II , where they served with Heavy Artillery Battalions ( " schwere Artillerie - Abteilungen " ) 624 , 641 and 815 as well as two Heavy Static Artillery Batteries ( " schwere Artillerie - Batterie bodenstandig " ) 230 and 779 . The 624th , 641st and 815th Battalions took part in the Siege of Sevastopol ( 1941 – 42 ) . It is unclear if the howitzers of the Romanian Army were employed on the Eastern Front and used against the Red Army . At least one M . 11 was seized from Yugoslavia and saw coastal defense service in the Adriatic as the 30 . 5 cm Mörser 639 ( j ) . It may have been upgraded somehow , as its Yugoslav designation was the 305 mm M 11 / 30 . The Hungarian Army ' s five guns served in the 101 . and 102 . artillery groups from 1938 and were used against the Yugoslavians and the USSR . Today , four weapons survive ; an M . 11 is in Rovereto , Italy ( Museo Storico Italiano della Guerra ) , a second is displayed in Belgrade ' s Military Museum and a third is in Bucharest , Romania along with the only surviving M . 16 .