Poison Gas at the Second Battle of Ypres

What happened

At the Second Battle of Ypres, German forces released chlorine gas along a stretch of the Allied line — the first large-scale use of a lethal chemical weapon in the war. The gas broke the line held by French and Algerian troops, but Canadian units helped prevent a decisive breakthrough.

Why it matters

Ypres introduced poison gas as a weapon of mass terror to modern warfare; gas would be used by both sides for the rest of the war.

Sources

• Imperial War Museums. Second Battle of Ypres, 22 April – 25 May 1915 · Reputable source