While much of the heavy artillery fanfare of World War 1 (1914-1918) goes to the German Empire's "Big Bertha" and similar heavy developments, the Austrian-Hungarian Empire itself produced a mammoth siege mortar as the 30.5cm (305mm/12in) Belagerungsmorser through the Skodawerke ("Skoda Works") concern. The gun was best recognized by its nickname - the "Schlanke Emma" ("Skinny Emma"). Their first combat exposure (coincidentally along with Big Berthas) was in Belgium at Liege against the supposedly impenetrable concrete-and-steel fortresses of the Belgian Army. This action took place on August 14th, 1914 and inevitably turned the Belgian fortresses into unrecognizable piles within just four days of heavy bombardment.
Schlanke Emma guns entered development in 1906 and persisted into 1911 before formal Austro-Hungarian Army adoption was to take place. The need for larger-caliber siege guns was pressed home by observed results of the Russo-Japanese War of 1904-1905 - in particular the famous Siege of Port Arthur (1904) which saw a resounding Japanese victory through the sinking of all Russian Navy capital ships in port under the force of German-originated Krupp heavy guns fired from land-based positions by the Japanese. This action forced a rethinking on the part of warplanners of the period, primarily where heavy artillery and siege warfare would be involved.
Production of the Schlanke Emma spanned from 1911 to the end of World War 1 in 1918 (November) to which 72 to 79 of the guns were completed (sources vary). Each system required a large team of 15 to 17 personnel to manage the various aiming, loading, reloading and transport functions of the weapon. The barrel measured 3.05 meters in length (rendered as "L/10" in army nomenclature) and of 30.5cm caliber firing massive 305mm shells down range. The barrel allowed for an elevation range of +40 to +70 degrees and reloading proved a time consuming process, allowing just one shot roughly every 3.5 minutes or so. The gun was mounted on the same carriage as used by the Austro-Hungarian Army's 24cm (240mm) L/40 cannon of 1916 - this also produced by Skoda.
The Schlanke Emma fired an 848lb (385kg) projectile made of nickel steel and proved extremely useful against hardened targets. A special "anti-infantry grenade" projectile was used against entrenched enemies and this version was also provided in a "lighter" 632lb (287kg) version. Soft targets could be engaged through the "Granatschrapnell" ("Grenade Shrapnel") round for an increasingly lethal effect on infantry, both physically and psychologically. These projectiles weighed 660lbs (300kg) and were completed with internal proximity fuses for timed results. The Schalnke Emma series featured muzzle velocities of 1,476 feet per second with ranges out to 7.6 miles (12.3km). Each completed system weighed 26 tons requiring use of artillery tractors for transport.
The Schlanke Emma was given military designations of M11, M11/16 and M16 throughout its war service. The M11/16 was a simpler design intended to improve mobility through a slightly lightened (25 tons) form. This variant was promptly introduced in 1916. The M16 was a heavily revised (and lightened) version of the M11, also introduced in 1916, with a new mounting system which allowed for 360-degree traversal to be achieved (through a central pivoting design). However, production of the 23-ton model totaled just 14 examples by war's end. During the war years, original guns (M11 / M11/16) were transported via the M12 artillery tractor while the later (M16) version was transported via the M17 tractor series. These heavy guns could also be affixed to stationary mountings for a more defensive-minded role.
After World War 1, surplus stocks of Schlanke Emma guns were taken on by Czechoslovakia (as the "30.5cm Mortar (t)") and Yugoslavia (as the "30.5cm Mortar 638(j)"), both nations having emerged from the Austro-Hungarian Empire's collapse. Captured Czech examples were then pressed into service for the German Army during World War 2 (1939-1945) and at least one example was present at the attacks against the famed French Maginot Line in June 1940. Still others were operated by German forces during the Siege of Sevastopol and Leningrad against the Soviet Union thereafter.