World War I Fast Facts

CNN Editorial Research

Updated 1312 GMT (2112 HKT) July 20, 2021

World War I ushered in an era of chemical weapons use that lingers, lethally, into the present day. About 1 million casualties were inflicted, and 90,000 were killed. Here, French troops wear an early form of gas mask in the trenches during the first widespread use of gas, by the Germans at the Second Battle of Ypres in 1916.
Photos: Photos: WWI chemical weapons
Chemical weapons in World War I – World War I ushered in an era of chemical weapons use that lingers, lethally, into the present day. About 1 million casualties were inflicted, and 90,000 were killed. Here, French troops wear an early form of gas mask in the trenches during the first widespread use of gas, by the Germans at the Second Battle of Ypres in 1916.
Hide Caption
1 of 8
French soldiers making a gas and flame attack on German trenches in Flanders, Belgium, in 1918. German forces were the first to open valves on gas cylinders, releasing the toxic cloud on unprepared French troops in Ypres in 1915.
Photos: Photos: WWI chemical weapons
Chemical weapons in World War I – French soldiers making a gas and flame attack on German trenches in Flanders, Belgium, in 1918. German forces were the first to open valves on gas cylinders, releasing the toxic cloud on unprepared French troops in Ypres in 1915.
Hide Caption
2 of 8
The bodies of hundreds of Italian soldiers are strewn across the battlefield, victims of a gas and flame attack during World War I, as others haul the wounded on stretchers. They were members of the Ninth Italian Regiment of the Queen's Brigade.
Photos: Photos: WWI chemical weapons
Chemical weapons in World War I – The bodies of hundreds of Italian soldiers are strewn across the battlefield, victims of a gas and flame attack during World War I, as others haul the wounded on stretchers. They were members of the Ninth Italian Regiment of the Queen's Brigade.
Hide Caption
3 of 8
Early gas masks were often ineffectual. The Germans and Americans would ultimately be the most successful in creating barriers to lethal gases. A German soldier shows how to wear one version.
Photos: Photos: WWI chemical weapons
Chemical weapons in World War I – Early gas masks were often ineffectual. The Germans and Americans would ultimately be the most successful in creating barriers to lethal gases. A German soldier shows how to wear one version.
Hide Caption
4 of 8
A soldier demonstrates an ungainly French gas mask. "French masks were notoriously unreliable,"<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2376985/" target="_blank"> wrote</a> historian Gerald Fitzgerald.
Photos: Photos: WWI chemical weapons
Chemical weapons in World War I – A soldier demonstrates an ungainly French gas mask. "French masks were notoriously unreliable," wrote historian Gerald Fitzgerald.
Hide Caption
5 of 8
A German cavalry unit with both horses and soldiers wearing gas masks advances during the Second Battle of the Aisne at Soissons, France, in June 1918.
Photos: Photos: WWI chemical weapons
Chemical weapons in World War I – A German cavalry unit with both horses and soldiers wearing gas masks advances during the Second Battle of the Aisne at Soissons, France, in June 1918.
Hide Caption
6 of 8