Nervegas History: One of the most terrifying weapons developed in World War I was poisoned gas. It was first used on the 22. of April 1915 by German troops in the 2. battle at . An English soldier describes the effect of chlorine gas this way: "It was beginning to get dark when this strange green cloud appeared from the German trench. Quickly the cloud approached the French trence. In this terrible night the Frence soldiers ran around terrified and blind. They fell moaning in pain as death sneaked into their lungs - a long deathfight with indescribable pain."