On April 22, 1915 at the Second Battle of Ypres, a strange gas floated across the battlefield. Believing the descending cloud to be a smokescreen, the French and Algerian Troops took no precautions to protect themselves. 5,000 soldiers became the first to lose their lives to a modern chemical weapon and 15,000 others were injured. Since then - and despite being prohibited in 1925 by the Geneva Protocol - chemical weapons have been used to devastating effect many more times.