White phosphorus smoke shells became available in small quantities in 1916, and in 1918 chemical and incendiary shells were provided. The latter was a shrapnel type shell using thermite pellets, although a black powder incendiary shell for AA use against Zeppelins was introduced in 1916. After the First World War, the variety of ammunition was reduced, although an armour piercing HE shell was developed. The main change was introduction of a new streamlined HE shell, 4/7.5 crh, giving a significant improvement in range. In the 1930s, the new generation of double base propellant, Cordite W, was also adopted.