The 15 cm schwere Feldhaubitze 18 or sFH 18 (German: "heavy field howitzer, model 18"), nicknamed Immergrün ("Evergreen"),[3] was the basic German division-level heavy howitzer of 149mm during the Second World War, serving alongside the smaller but more numerous 10.5 cm leFH 18.

Its mobility and firing range and the effectiveness of its 44 kilogram shell made it the most important weapon of all German infantry divisions.

In the end the army decided the solution was to combine the best features of both designs, using the Rheinmetall gun on a Krupp carriage.

This led to numerous efforts to introduce new guns with even better performance than the ML-20, while various experiments were also carried out on the sFH 18 to improve its range.

These led to the 15 cm sFH 18M version with a removable barrel liner and a muzzle brake that allowed a larger "special 7" or 8 charge to be used.

19 FES ammunition, which used a rocket-assisted round that could reach 18,200 metres (19,900 yd) and give it some level of parity with the ML-20.