Chlorine gas during World War I
Chlorine gas is a poisonous chemical weapon that was first used on 22 April 1915, when the Imperial German Army bombarded Canadian and French Army troops at Ypres with 168 tons of chlorine gas during World War I. The Germans' gas caused the lungs of the Allied troops to fill with fluids, and soldiers choked to death as their lungs burned; it was a cruelly effective weapon. The use of chlorine gas in battle, especially after the Third Battle of Ypres, led to both sides adopting teh use of gas masks, which became standard issue for every soldier serving on the front lines of the war. 1,300,000 people were killed or wounded by chemical weapons at the end of the war, and chemical weapons were banned under the 1925 Geneva Protocol. However, chlorine gas would continue to see service in several conflicts, most recently the Syrian Civil War.