The First Use of Chemical Warfare - Gas Attack, Ypres, 1915 This 5 page report discusses a single battle, at Langemarck, near Ypres, on April 22, 1915, that changed the conduct of war forever. The introduction of chemical warfare created an entirely different military realm in terms of the scope and effectiveness of battle that was moving toward resolution (at best) and accelerated growth. By 1918, one in every four shells on the Western Front was a gas shell. Bibliography lists 4 sources.