The Nebelwerfer was initially designed for launching smoke, poison gas and high explosive shells. Early models were similar to heavy mortars, but in 1940 the first rocket-propelled Nebelwerfer were issued and these were capable of delivering smoke and gas, but were mainly used to fire high explosive. They fired a spin-stabilized rocket which was supposed to give more accuracy but left a smoke trail which made it vulnerable to counter fire. Later models fired an incendiary round which was used in conjunction with high explosive rounds. Nebelwerfers were built in various calibres and mounted on a number of different carriages and vehicles and these were used as a saturation weapons until the end of the war.