The Chauchat was the standard light machine gun or "machine rifle" of the French Army during World War I (1914–18).
Its official designation was "Fusil Mitrailleur Modele 1915 CSRG" ("Machine Rifle Model 1915 CSRG").
The Chauchat was one of the first light, automatic rifle-caliber weapons designed to be carried and fired by a single operator and an assistant, without a heavy tripod or a team of gunners.
It set a precedent for several subsequent 20th-century firearm projects, being a portable, yet full-power automatic weapon built inexpensively and in very large numbers.
The chronology of the patents makes it clear that Louis Chauchat had simply borrowed the mechanical principles of an already-existing long barrel recoil, semi-automatic rifle filed by John Browning in his milestone of October 16, 1900.
None of these CS machine rifles have survived, either in public museums or in private collections.
It was clear that this type of weapon had become indispensable in modern warfare, because of the increase in firepower it could provide to an infantry section.
Spurred by General Joseph Joffre, it was decided to adopt the Chauchat, above all else because the pre-war CS (Chauchat-Sutter) machine rifle was already in existence, thoroughly tested, and designed to fire the 8mm Lebel service ammunition.
Not less than eight trial prototypes were tested at APX, between 19.
As a result, a small series (100 guns) of 8 mm Lebel CS (Chauchat-Sutter) machine rifles was ordered in 1912, then manufactured between 19 by Manufacture d'armes de Saint-Étienne (MAS).
A total of 262,000 Chauchats were manufactured between December 1915 and November 1918, including 244,000 chambered for the 8mm Lebel service cartridge, making it the most widely manufactured automatic weapon of World War I.