The 15cm schwere Feldhaubitze 18 or sFH18 (German: “heavy field howitzer, model 18”), nicknamed Immergrün (“Evergreen”), was produced by Rheinmetall and Krupp companies and adopted by the German army in 1935. It was the first artillery weapon equipped with rocket-assisted ammunition to increase range. The 15cm sFH18 was also used in the self-propelled mounting of the Hummel.
By the outbreak of war the Wehrmacht had about 1,353 of these guns in service. Production continued throughout the war, reaching a peak of 2,295 guns in 1944. A total of 5,403 sFH 18 howitzers were produced.