Hydrogen cyanide had been discovered in the late 18th century and was usually used in California for the fumigation of citrus trees. In 1919, the Deutsche Gesellschaft für Schädlingsbekämpfung mbH (Degesch) was founded in Germany. This was a state-controlled group to investigate military uses of the chemical. The new product was marketed as a pesticide, Zyklon, but was soon banned as being similar to a mixture used in World War I as a weapon.
Zyklon B was recreated by Degesch, after Degesch came under new management, and eventually after achieving a patent, Walter Heerdt was named as its inventor.
- Hayes, Peter 2004. From cooperation to complicity: Degussa in the Third Reich. Cambridge; New York; Melbourne: Cambridge University Press. ISBN 0-521-78227-9
- Burnett, John 2006. The Bath Riots: indignity along the Mexican border