Chemical Warfare in Europe

The first formal treaty that forbade something that you could call chemical warfare was probably the Franco-German treaty of 1675. In 1874, about a dozen European states signed the Brussels Declaration, which banned poison gas and other poisons as weapons of war. The first modern chemical weapons attack on a huge scale occurred at Ypres in Belgium on April 22, 1914. By the end of World War I, there'd been a grand total of 3,000 different chemical agents tested as potential weapons.