What was the main reason for the use of poisonous gases during the war?

Breaking the deadlock of trench warfare

The introduction of poisonous gases on the battlefields of World War I was primarily aimed at breaking the deadly stalemate of trench warfare. The use of these chemical weapons introduced a new element of terror and marked a turning point in the conduct of warfare, where moral and ethical boundaries were increasingly blurred. The first large-scale deployment of chlorine gas by Germany at Ypres in 1915 demonstrated its destructive potential, but also led to the rapid development of countermeasures, such as gas masks. This arms race in chemical warfare underscored the brutality and desperate innovation of modern warfare.