A new very light and portable mortar to replace the V-B rifle grenade was one of the facets of the French plan for rearmament and modernization after World War Two. The concept for the weapons that would become the L.Gr. Mle 37 was first requested in 1924 - but like so almost all the other parts of that arms program, it was crippled by delays through the 1920s and 1930s. Only in the late 1930s when was was looking imminent did the program finally move forward.

The design, created by Captain Nahan of the Chatellerault arsenal, was adopted in 1937 and a whopping 21,950 were ordered in January of 1938 - and the order was quickly revised up to 50,000. However, only 2900 had been produced by the time of the armistice in June 1940. Production resumed in 1944, and the launcher did see use in Indochina. In addition, its 50mm grenade was the basis for the postwar French rifle grenades, as used on the MAS-36 LG 48, the MAS-44, and MAS-49 rifles. As fired form the mortar, the projectile weighed about one pound (0.4kg) and had a range of 80 to 460 meters, with an effective rate of fire up to 20 rounds per minute.