How to build the 21 cm Nebelwerfer 41 and 42 (15 and 21 cm NbW 42) were a German multiple rocket launcher used in the Second World War.

It served with units of the Nebeltruppen, the German equivalent of the American Chemical Corps. Just as the Chemical Corps had responsibility for poison gas and smoke weapons that were used instead to deliver high-explosives during the war so did the Nebeltruppen. The name “Nebelwerfer” is best translated as “Smoke Mortar”. It saw service from 1942–45 in all theaters except Norway. The Nebelwerfer 42 – 21cm (210mm) was adapted for aerial combat by the Luftwaffe in 1943