Some of the Artillery pieces used by the German Army in the Great War were not, technically speaking, artillery pieces at all, but heavy mortars: and of these, that were employed in large variety, the most important were the Minenwerfer (literally: "Mine Throwers") or medium mortars of 17cm calibre and the heavy mortar of 25 cm calibre. The latter type was a much sought after support weapon, which is needless to say, as it could fire projectiles with an explosive power that was much greater than artillery projectiles of the same calibre.
The reason for this is, that because of the relatively low pressures in the mortars barrel, as compared to, say, an equal sized howitzer, the casing of the mortar projectile could be made thinner, allowing for a bigger load of explosives. A grenade from a sMW thus contained some 47 kilos of TNT, which actually equals the explosive power contained in almost 250 7.7cm early type of HE/Shrapnel grenades! Needess to say, used properly, the effect could be absolutely horrific.
The Minenwerfer originally started as a specialist weapon for the Engineer branch of the Army, thought to be used primarily against obstacles hard to get at by traditional engineer means and by artillery. What the designers at Rheinmetall came up with, was essentially a scaled down howitzer, with a rifled barrel, a hydro-pneumatic recoil mechanism and a standard dial sight. It was, however, muzzle-loaded. At the outset of the war, some 44 of these heavy Minenwerfer had been issued to the troops, and being a well-kept secret, they came as a nasty surprise to the enemies of the German Army, first the Belgians - who were first subjected to them during the German attack at Liège and Namur, then the French and British.
In 1916 a new (n.A) version with a longer barrel entered service, however both the old (a.A) 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 its 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 (n.A) version could fire a full size shell up to 1000 meters. The full size weighed 97kg, and the half size weighed 60 kg. The full size shell could penetrate up to 9m of earth making it an effective weapon against dugouts and other fortifications.
The sMW was very heavy and cumbersome to handle: it took some 21 men to move it. It came equipped with special wheels, that were removed when the mortar was emplaced. Still, despite its drawbacks, it was produced in great numbers. The reason was partly the effect: it was a fearsome weapon. But also, it made sense economically to employ this weapon. It was 10 times cheaper to manufacture than the 42cm Big Berthas, but it was almost equal in effect. Additionly the ammunition were also cheaper, as it did not need any costly metal for the cartridge. Mortars have always been the poor man’s artillery, and it was very much so with the sMW.
The sMW was not a troop weapon per se, being used simply for local fire support, at the beck and call of the local commanders. The use of the gun was often strictly centralized, the batteries being tightly controlled by the artillery commanders, giving them the role of supplementing the ordinary artillery. In the attack, batteries of sMW were almost invariably used for making an enemy position "ripe for assault" - sturmreif. All large calibre weapons were used for this. Field Guns and lighter Minenwerfers, were primarily used for supression or interdiction. For instance, during the breaking of the Russian front at Riga, in early September 1917, around 100 had been gathered, and were used, with telling effect.
The drawing is based on measurements and pictures taken in in the Koninklijk Belgisch Legermuseum in Brussels and the Wehrtechnisches Museum in Koblenz.
The following images are of a surviving sMW, at the Army Museum in Brussels.
| Calibre | 25 cm |
| Weight of Gun | 660 kg (a.A) 780 kg (n.A) |
| Barrel Length | 750mm (L/3) a.A 1250mm (L/5) n.A |
| Max. Range | 563m (a.A) 1077 (n.A) |
| Muzzle Velocity | 200 m/sec |
| Min./Max. Elevation | +45°/+75° |
| Traverse | 12° |
| Shell Weight | 97 kg (HE) |
Fine Scale Factory makes the only kit of the 25cm sMW that I know of - see kit reviews section.