The Second Battle of Ypres introduced poison gas to the Western Front in 1915.
In April 1915, German forces released 168 tons of chlorine gas, marking the first mass use of chemical weapons in the First World War. The attack created a terrifying, suffocating cloud that forced Allied troops to flee, fundamentally changing the nature of combat and sparking a desperate race for protective technology.
The Second Battle of Ypres, fought from 22 April to 25 May 1915, centered on controlling high ground near the Belgian town of Ypres. German General Erich von Falkenhayn authorized the use of chlorine gas to facilitate troop transfers to the Eastern Front. Chemists Fritz Haber, Walther Nernst, Otto Hahn, James Franck, and Gustav Hertz supervised the installation of 5,730 cylinders, which relied on a breeze to carry the vaporized liquid toward Allied lines.
On 22 April, the gas cloud hit French divisions, causing thousands of casualties and leaving a 3.7-mile gap in the line. Soldiers described the experience as a slow, agonizing death by suffocation, often compared to drowning on dry land. While some troops panicked, others held their ground. Canadian and British forces, initially caught off guard, eventually stabilized the front, though the city of Ypres was ultimately demolished by artillery fire.
The immediate Allied response to the gas was primitive; soldiers were advised to urinate on cloths to neutralize the chlorine. By July 1915, more efficient respirators were issued, though early versions remained inadequate. The battle resulted in massive casualties—estimates suggest over 59,000 British and 35,000 German losses—and catalyzed a long period of experimentation in chemical warfare and defensive gear, including the later development of the P and PH helmets.
Beyond the tactical shifts, the battle left a profound cultural legacy. During the fighting, Lieutenant Colonel John McCrae wrote the poem "In Flanders Fields," which remains a central part of modern remembrance. The engagement also highlighted the unpreparedness of infantry for modern, machine-gun-heavy warfare, forcing a re-evaluation of tactical units and artillery coordination that would continue throughout the war.
Source: Second Battle of Ypres
