During World War I, Fritz Haber became a staunch supporter of the German military effort and played an important role in the development of chemical weapons (particularly poison gases). His efforts would culminate in his supervision of the first successful deployment of a weapon of mass destruction in military history, in Flanders, Belgium on 22 April 1915. Immerwahr spoke out against her husband's research as a “perversion of the ideals of science” and “a sign of barbarity, corrupting the very discipline which ought to bring new insights into life.” Immerwahr was also a witness to the accidental death of one of her former college classmates, Otto Sackur, who was attempting to tame cacodyl chloride in Haber's lab as part of Haber's research into chemical weapons.