[1] It was based on the earlier 21 cm Mörser 10 but had a longer barrel, a gun shield and other refinements.

Originally, it broke down into two loads for transport but the Germans rebuilt surviving guns during the 1930s with rubber-rimmed steel wheels to allow for motor traction in one piece with a limber under the trail and generally removed the gun shield.

Sweden bought a dozen weapons in 1918 from the Germans and they remained in service until 1950.

The Swedes had their own concrete-piercing shells, called 210 tkrv 51/65-ps R-/33 by the Finnish army, weighing 120.75 kg (266.2 lb), which had dispersion problems as the Finns found out.

The weapons were put into reserve after the war and remained there until the late 1960s before being discarded.