Arguably, the history of Degussa's role in the manufacture of Zyklon B belongs under the heading of war production. From 1939 to 1945, the predominant uses of this vaporizing pesticide were to fumigate military quarters, supplies, uniforms, vehicles, rolling stock, and vessels; to do the like in connection with the forced labor and ethnic German repatriation programs; and to secure food supplies through the disinfestation of storehouses and milling installations. But these now largely forgotten functions do not explain the enduring infamy of the substance. Even today many people instantly recognize the brand name – certainly far more of them than can identify the companies that owned it – because of a purpose to which perhaps 1 percent of the chemical sold during the war years was put. Between 1941 and 1945, the SS applied Zyklon B on a massive scale at Auschwitz – and to lesser extents at Majdanek, Mauthausen, Stutthof, Neuengamme, Natzweiler, and possibly Dachau and Sachsenhausen – to asphyxiate some 1 million people, nearly all of them Jews. Measured by historical impact rather than relative usage at the time, Zyklon B was no mere military or agricultural product, but an instrument of mass murder. Degussa's part in the manufacture and deployment of the commodity therefore demands separate and close analysis.

Both the use of hydrogen cyanide gas as an insecticide and Degussa's interest in the product antedate the First World War, but the conflict greatly accelerated the two developments.