A sFH 18 firing at French or British positions during the invasion of France. May 1940
(Bundesarchiv Bild 101l-054-1527-14)

sFH 18 in France

A 15 cm schwere Feldhaubitze 18 nicknamed the Immergrun (evergreen), It was, however, the first artillery weapon equipped with rocket-assisted ammunition to increase range. The sFH 18 was also used in the self-propelled artillery piece schwere Panzerhaubitze 18/1 (more commonly known as Hummel). Against the Soviet Union however, the sFH 18 proved to be greatly inferior to the Red Army corps artillery 122 mm howitzer and 152 mm ML-20 gun-howitzer.
(Bundesarchiv Bild 101I-078-3073-23A)

Immergrün 

German troops loading a 15 cm NbW 41 rocket launcher, near Kursk, Russia, summer 1943.
(Bundesarchiv Bild Bild 101I-022-2943-20)