On 22 April 1915, during the Second Battle of Ypres, German forces introduced a horrifying new weapon to the First World War: Chlorine gas.
Released from over 5,000 cylinders along a four-mile front, the toxic green cloud drifted towards Allied trenches, causing panic, suffocation, and devastation among French and Canadian troops.
The attack, which marked the first large-scale use of chemical weapons in modern warfare, killed thousands and shocked the world, ushering in a grim new era of industrialised combat.
