10. The poison gas silenced French artillery in June prior to an assault
French gas masks early in the battle were effective against the gases fired via German artillery shells, allowing the French artillery to continue firing. On June 22, 1916, the Germans used diphosgene gas, firing over 116,000 shells containing the gas known as Green Cross against the French artillery. Green Cross shells were so named because of the markings put on the shells to identify them to the German gunners. The gas acted as a pulmonary agent, and the bombardment largely silenced the French artillery. The attack was followed by an infantry assault the following day, which created a bulge in the French defenses.
It was following the attack on June 23 that the French commander, General Nivelle, issued the famous order to his troops, “they shall not pass”. What he actually said was, “Vous ne les laisserez pas passer, mes camarades” (You will not let them pass, my comrades). The French recaptured most of the bulge in the ensuing days, as the Germans had exhausted their supply of Green Cross shells. They also had no way of supply the men occupying the bulge, who quickly ran out of water. The village of Fleury, in the area of the bulge, was passed back and forth between the Germans and the French no less than sixteen times before the end of August.