The wind had been wrong for days, and 168 tons of death waited in pressurized cylinders for the breeze to shift toward the Allied trenches.

The Devil's Breath: Germany Unleashes Chemical Horror at Ypres

On April 22, 1915, a greenish-yellow cloud drifted across the trenches — and warfare changed forever

Germany's first major poison gas attack at Ypres opened a four-mile gap in Allied lines and changed warfare forever.

The wind had been wrong for days. German soldiers in the trenches near Langemarck, Belgium, had waited with growing unease beside 5,730 cylinders containing 168 tons of chlorine gas. Finally, at 5:00 PM on April 22, 1915, the breeze shifted. Hauptmann Otto Peterson gave the order. Valves turned. And hell rose from the earth.

French Territorial and Algerian troops holding the northern sector of the Ypres Salient saw it first — a strange yellowish-green mist, perhaps six feet high, rolling toward them across no man's land. Some thought it was a smokescreen. Others, more experienced, noticed how birds fell dead from the sky ahead of it.

Within minutes, the chlorine reached the Allied lines. Men clawed at their throats as the gas attacked mucous membranes, filling lungs with fluid. The French colonial troops, having never seen anything like this invisible enemy, broke and ran. A four-mile gap opened in the Allied line — the largest breach on the Western Front since trench warfare began.

Pte. Anthony Hossack of the Queen Victoria Rifles watched from a neighboring sector: "830 men lay dead from choking... greenish faces staring at us from the ground, mouths agape." The gas was heavier…

💡 Canadian soldiers discovered that urinating on cloth and holding it to their faces offered crude protection against chlorine gas — the ammonia partially neutralized the chemical.