What significant new weapon was first used against French and Canadian troops at the Battle of Ypres?

The introduction of chlorine gas at the Battle of Ypres in 1915 marked a pivotal moment in warfare, as it was the first large-scale application of chemical weapons in combat. This new tactic aimed to break the stalemate of trench warfare by causing panic and confusion among troops, resulting in significant psychological and physical effects. Chlorine gas was delivered via canisters, and when the wind was favorable, it would fill the trenches, impairing the ability of enemy soldiers to fight effectively. This represented a shift towards more modern and horrific methods of warfare, challenging traditional combat norms and leading to future developments in chemical weaponry. The usage of chlorine gas at Ypres solidified its place in military history, highlighting the evolving nature of warfare during World War I.