After 10 days waiting for favorable winds, the German Army uses chlorine gas on the battlefield at Flanders, the first use of any chemical weapon. After a still morning and afternoon, 5000 gas cylinders are opened at 5 p.m. Under attack from the yellow-green cloud of gas, French commander Georges Lamour calls headquarters:
All my trenches are choked. I am falling myself!
1,200 French soldiers are killed in the first five-minute gas attack and the fighting that followed. Lamour is never found. Once the gas cleares, German soldiers make more progress than they have in months. Within an hour they have opened a gap of more than 6 kilometers (4 miles) with Ypres nearly in their hands. However, the Germans do not take advantage of the situation and do not break through the line.