Couple of dozen soldiers standing in a field, doing a gas mask drill.
Most likely an official French Army photo.
Written in pencil on back: “01984”.
(See also two others photo for sale of American soldiers in gas masks.)
Paper is 'warped'.
18 x 12.5 cm / 7-1/8” x 5“.
The first large scale use of chemical weapons was during World War I. They were primarily used to demoralize, injure, and kill entrenched defenders, against whom the indiscriminate and generally very slow-moving or static nature of gas clouds would be most effective. The types of weapons employed ranged from disabling chemicals, such as tear gas, to lethal agents like phosgene, chlorine, and mustard gas. This chemical warfare was a major component of the first global war and first total war of the 20th century. The killing capacity of gas was limited, with only about 90 thousand fatalities from a total of some 1.2 million casualties caused by gas attacks. Gas was unlike most other weapons of the period because it was possible to develop effective countermeasures, such as gas masks. In the later stages of the war, as the use of gas increased, its overall effectiveness diminished.