Canadian soldier being treated for Mustard Gas injuries, 1917 - 1918. Today 106 years ago, on July 12, 1917, the German Army deployed Mustard Gas through shells on British forces at Ypres for the first time in the First World War. Since the German Army on the Western Front would spend the second half of 1916 and almost all of 1917 defensively against relentless Allied offensives, the Germans began the devoloment of a new gas designed as a defensive agent. Dichlorodiethyl sulfide (C4H8Cl2S) was the result, best known as Mustard Gas for its pale brown-yellow colour and distinct sweet and mustard-like odor. Though the substance wasn't actually a gas in itself, but tiny condensed liquid droplets, which evaporated in sunlight. Exposure to Mustard Gas caused blisters on skin, sore eyes which could lead to blindness, victims would vomit, suffer respiratory damage and suffer external and internal bleeding. Dying from Mustard Gas was an extremely painful process which could take several wee...