section_path: Casualties/War crimes/Chemical weapons in warfare
section_name: Chemical weapons in warfare
paragraph_text: Chemical weapons in warfare
  
  The German army was the first to successfully deploy chemical weapons during the Second Battle of Ypres (April–May 1915), after German scientists under the direction of Fritz Haber at the Kaiser Wilhelm Institute developed a method to weaponize chlorine. The use of chemical weapons had been sanctioned by the German High Command to force Allied soldiers out of their entrenched positions, complementing rather than supplanting more lethal conventional weapons. Chemical weapons were deployed by all major belligerents throughout the war, inflicting approximately 1.3 million casualties, of which about 90,000 were fatal. The use of chemical weapons in warfare was a direct violation of the 1899 Hague Declaration Concerning Asphyxiating Gases and the 1907 Hague Convention on Land Warfare, which prohibited their use.