Chemical weapons in World War I volatile oily liquid. It was introduced as a vesicant by Germany in July 1917 prior to the Third Battle of Ypres. The Germans marked their shells yellow for mustard gas and green for chlorine and phosgene; hence they called the new gas "Yellow Cross". It was known to the British as "HS" ("Hun Stuff"), and the French called it "Yperite" (named after Ypres). Mustard gas is not an effective killing agent (though in high enough doses it is fatal) but can be used to harass and disable the enemy and pollute the battlefield. Delivered in artillery shells, mustard gas was
French Army in World War I German army in August 1914; however, the Germans were the first to seriously research chemical warfare. Poison gas (chlorine) was first used on April 22, 1915, at the Second Battle of Ypres, by the German army. April 1915 saw the first innovation in protection against chemical warfare: a cotton pad dipped in bicarbonate of soda, but by 1918, troops on both sides had charcoal respirators. By November 11, 1918, France had suffered 190,000 chemical warfare casualties, including 8,000 dead. At the outbreak of war the French Army retained the colourful traditional uniforms of the nineteenth century for active service wear.