21cm Morser L/12 (M1910)

The 21cm Morser L/12 was the standard German army heavy mortar at the start of the First World War.

The first modern heavy mortar to enter service in the German army was the 21-cm Morser M1899, but this was a simple weapon without barrel recoil. Krupp and Rheinmetall both produced prototypes of a 21cm mortar with barrel recoil, the 21cm Versuchs Morser L/10 (Krupp) and 21cm Versuchs Morser L/12 (Rheinmetall), but by the time these were ready they lacked the range required by the German army.

21cm Morser L/12 (M1910) near Arras, May 1917
21cm Morser L/12 (M1910) near Arras, May 1917

In 1907 the Artillery Testing Commission issued specifications for a 21cm Mortar with a range of over 9,000m. Rheinmetall produced the 21cm Versuchs Morser L/15, while Krupp produced the shorter 21cm Morser L/12. This was a fairly unusual looking weapon, with the barrel almost surrounded by the recoil mechanism, and a small splinter shield, presumably to protect the crew from the effects of the mortar’s own fire. Otherwise it had a fairly standard chassis for the period, with heavy spoked wheels and a box trail.

The Krupp mortar won the contest, and was accepted by the Army in February 1910. It was quickly issued to all batteries in the heavy and siege artillery. This was a fairly large scale undertaking - each mortar had to be carried in three loads, each requiring six heavy horses, and each mortar battalion had four mortars, for a total of 72 horses just for the mortars. By July 1914 256 Mortar L/12s had been issued, of which 224 were in use with the mobile heavy artillery and reserve Fussartillerie and 32 were located in fortifications.

21cm Morser L/12 (M1910), September 1918
21cm Morser L/12 (M1910), September 1918

As the war went on the number of mortars in a battalion was altered to two batteries of two mortars, and as late as October 1918 there were still 219 in service with 73 battalions. However by this point it had been superceded by the long barrel 21cm Mortar L/14.6, of which twice as many were in service.


21cm Mortar L/12



Barrel Length

2,530mm (L/11.9)

Weight for transport


Weight in action



0 to 42 degrees


4 degrees

Shell Weight


Muzzle Velocity

367 m/sec

Maximum Range


Rate of Fire

One round per minute

German Artillery 1914-1918, Wolfgang Fleischer. Covers over 100 guns used by the German Army and shore detachments of the Navy during the First World War, a conflict largely dominated by artillery. Each one gets a brief description, a set of technical stats and a good picture. Shows the wide range of gun types and sizes used by the Germans during the First World War, and the way in which they evolved to deal with the unexpected challenges of trench warfare. [read full review]
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Books on the First World War | Subject Index: First World War

How to cite this article: Rickard, J (27 April 2018), 21cm Morser L/12 (M1910) , http://www.historyofwar.org/articles/weapons_21cm_morser_L12_M1910.html

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