Zyklon B is functionally the same as its predecessor, Zyklon A. In fact the primary difference is that Zyklon A had a very distinct warning odor. It was originally used as a potent pesticide, and it worked very well, being Cyanide-based.
The man who created this was a chemist from Breslau named Fritz Haber. He basically was singlehandedly responsible for pushing for gas warfare.
After his death, his Institute reformulated Zyklon A to remove the telltale odor from it, so people wouldn't suspect the gas was being used until it was too late.
It was this reformulated pesticide that was used to murder concentration camp prisoners in Germany and German-held territories.
By the spring of 1942, both the Auschwitz-Birkenau and Majdanek camps had come to prefer it as the tool by which to exterminate prisoners. It would go on to kill approximately 1.2 million people by war's end. In fact, the actual Commandant of Auschwitz - Rudolf Hoss - gave the name of a subordinate of his who developed the INITIATIVE (read: plan) to use Zyklon B to kill Russian POWs in August of 1941. This man was Captain Karl Fritzsch. After Hoss observed the repeating of the application of gas on more Russian prisoners in September that year.
(see Hoss, Death Dealer, pp. 155-56, cited in Christopher Browning. The Origins of the Final Solution (Nebraska University Press/Yad Vashem, 2004), pp. 526-27, n. 208, 209, 210.)
Post Edited (24-Aug-12 16:29)