The German Army had learned the lessons from the Russo‑Japanese war of 1904-05, where the Japanese used makeshift weapons to hurl explosive demolition charges to destroy enemy fortifications. Their material effect was just as good as the quality of the weapon, being zero all round. But the German observers must have had a shrewd idea what the effect might have been, had these weapons been constructed properly. Back in Germany the Fortress Pioneer Battalions began lobbying for the development of such weapons. By 1910 they were equipped with the first mortar, the heavy Ehrhardt. These were constructed for engaging enemy fortifications. The medium mortars, which followed shortly after that, were intended as fortification artillery.

When the front became stationary, and there was no sign of threat to the German cities, they were gradually moved up to the front. It is often said that the only military use of these mortars was to affect the enemy’s morale, but in trench warfare these guns could destroy a whole section of trench and were quite deadly. Their penetration was fierce, especially the heavy shells. As the Allied shelters were not too deep, being technically the force that was on the move to liberate, these shells were more than a match for their shelters.

In 1916 the artillery was reorganised. It was split in 2 forces. You had the basic artillery, each type of gun with its specific task, and the infantry artillery. By now the idea had set in that these mortars were no longer a pioneering tool to smash fortifications, but a weapon intended to support the infantry. They had a mixed role. During the artillery preparation before a battle they fell under the divisional artillery, and their mission was to clear barbed wire, smash enemy trenches or (shallow) dugouts and machine gun positions. This was only done by the heavy and medium mortars. When the moment of attack came, they were placed under the command of the various infantry divisions, and they followed closely after the first wave. Here their mission was to take out any strong points and to reduce resistance to dust. This was done by the light and medium mortars, as the heavies were too cumbersome to move. Towards the end of the war the organisation of an ‘Abteilung’ was normally four heavy guns and eight medium ones.  

This howitzer was intended for destroying fortifications. They were stationary, and only fired during the preparation. In 1916 a new version with a longer barrel entered service, however both the old and the new versions remained in service until the end of the war. They were also used in the uprising of 1919, but they were handed over to the allies under the Treaty of Versailles. These howitzers could fire a full shell, a half shell (which was, contrary to it’s name, not even half as effective), and a quarter shell. This shell was similar in size as the half size one. They were prone to premature detonation, and the cold weather made the barrel brittle, which increased this problem. The old gun could fire a full size shell up to 550 meters, and a half shell up to 800 meters. The new version could fire a full size shell up to 1000 meters. The full size weighed 97kg, and the half size weighed 60 kg. To my knowledge, these guns could only fire HE shells, and not gas shells. There was not much point to firing gas shells with the heavy mortar because the whole purpose of these guns was to fire large explosive charges with direct fuses, to do as much damage to the enemy as possible. This could not be done by the medium gun, so gas shells were restricted to the medium mortars.

The 25 heavy shell could penetrate as deep as 9 meters of earth, so anything but the deepest of dugouts were safe from its claws.

Calibre: 25cm
Barrel lenght in calibres: 3 (a/A) or 5 (n/A)
Weight: 660 kg (a/A) or 780 kg (n/A)
Range of fire: 563 m (a/A) or 1077 m (n/A)
Weight of shell: 97kg

These drawings are based on measurements and pictures taken in in the Koninklijk Belgisch Legermuseum in Brussels and the Wehrtechnisches Museum in Koblenz.