Negotiation history thumb|right|British troops blinded by poison gas during the Battle of Estaires, 1918 In the Hague Conventions of 1899 and 1907, the use of dangerous chemical agents was outlawed. In spite of this, the First World War saw large-scale chemical warfare. France used tear gas in 1914, but the first large-scale successful deployment of chemical weapons was by the German Empire in Ypres, Belgium in 1915, when chlorine gas was released as part of a German attack at the Battle of Gravenstafel. Following this, a chemical arms race began, with the United Kingdom, Russia, Austria-Hungary, the United States, and Italy joining France and Germany in the use of chemical weapons.
Negotiation history thumb|right|British troops blinded by poison gas during the Battle of Estaires, 1918 In the Hague Conventions of 1899 and 1907, the use of dangerous chemical agents was outlawed. In spite of this, the First World War saw large-scale chemical warfare. France used tear gas in 1914, but the first large-scale successful deployment of chemical weapons was by the German Empire in Ypres, Belgium in 1915, when chlorine gas was released as part of a German attack at t.he Battle of Gravenstafel. Following this, a chemical arms race began, with the United Kingdom, Russia, Austria-Hungary, the United States, and Italy joining France and Germany in the use of chemical weapons.