Poison Gas in WWI
The chemical weapon that made the First World War a byword for industrial cruelty, from chlorine clouds at Ypres to blistering mustard gas.
The wind had to be right. On 22 April 1915, near the Belgian town of Ypres, German troops opened the valves on thousands of steel cylinders and let the breeze carry a grey-green cloud of chlorine across the open ground. It settled into the trenches of two French divisions, the colonial 45th (Algerian) Division and the metropolitan 87th Territorial Division of older French reservists. Men who breathed it clawed at their throats as the gas reacted with the moisture in their lungs to form acid. Within minutes a four-mile hole opened in the Allied line. Modern chemical warfare had arrived, and with it a horror that made the First World War a byword for industrial cruelty.
Escalation
Chlorine was only the beginning. It was visible, it smelled of pineapple and pepper, and a wet cloth over the face blunted it, so both sides raced for something worse. Phosgene came next, nearly colorless and far deadlier, its damage often delayed a full day so that a soldier felt fine at dusk and drowned in his own lung fluid by dawn. It would cause the majority of the war's gas deaths. Then, in July 1917, the Germans introduced mustard gas near Ypres, and gas warfare reached its final, sadistic form. Mustard was not primarily a killer. It was a blistering agent that burned exposed skin, blinded eyes, and seared the lungs, and because it was an oily liquid that clung to soil, clothing, and shell craters, it could poison a stretch of ground for days after the attack.
Masks and arithmetic
Every new agent triggered a new defense. The improvised cotton pads of 1915 gave way to hooded gas helmets and then to the box respirator, a rubberized mask linked by hose to a canister of absorbent chemicals. Soldiers drilled to don them in seconds at the cry of 'Gas!' and horses and mules were fitted with their own. The result was a grim cat-and-mouse in which each side's chemists tried to outrun the other's filters.
The arithmetic is worth stating plainly, because the terror outran it. Gas killed perhaps 90,000 to 100,000 men and wounded well over a million, a fraction of the millions cut down by artillery and machine guns. Shells were far more efficient killers. But gas did something shells did not: it turned the air itself into an enemy, killed slowly and invisibly, and left survivors coughing and half-blind for the rest of their lives. That is why it lodged in memory out of all proportion to the body count, in Wilfred Owen's poem of a man 'guttering, choking, drowning,' and in the photographs of blinded soldiers filing along with a hand on the shoulder of the man ahead.
The line that mostly held
The revulsion had consequences. In 1925 the major powers signed the Geneva Protocol, banning the use of chemical and biological weapons in war. It was an imperfect document that did not forbid making or stockpiling them, and it was broken in colonial wars and, monstrously, in the Nazi death camps. But on the battlefields of the Second World War, where every major army held stockpiles ready, gas was almost never used. The men of 1915 had made the weapon so infamous that even Hitler flinched from turning it loose at the front. The cloud at Ypres still marks the edge of what soldiers agreed not to do.