A hundred years ago, on 22 April, poison gas was first used in warfare. Though about 95% of casualties in WW1 were caused by explosives, sickness and malnutrition, there is a peculiar horror associated with the use of chemical weapons. It is also true that, apart from isolated examples, WW1 was the only instance of the systematic and widespread use of gases in war (see Box 1).
As early as 1854, the British Secretary for Science and Art, Lyon Playfair [sic], suggested bombarding the Russians in Crimea with shells filled with cacodyl cyanide, an evil-smelling substance which vapourises easily.1 Containing arsenic and cyanide, it is extremely poisonous. It was rejected by the military as being equivalent to “poisoning the wells of the enemy.” Playfair thought this argument was ridiculous since armies were quite prepared to cut people to pieces with shrapnel. He thought poison gas was a more humane way of killing the enemy.2
By 1915, both sides had already used tear gases and irritants and, despite military objections and the banning of poison gas projectiles by the 1907 Hague Convention, both would soon use lethal gases. The Convention was circumvented by releasing these gases from cylinders (Fritz Haber’s idea) when the wind was right: soon it would simply be ignored.