In the late 1940s, French engineers initiated the development of the Lorraine 40t, a lighter tank project intended to complement the AMX-50 heavy tank. Mounted on the chassis of the Canon d'Assaut Lorraine, the tank featured an oscillating turret and utilized advanced technologies from previous experimental projects like the CA Lorraine and the AMX-50 prototype, including the revolver autoloader. Despite its maximum 45 mm armour thickness, the Lorraine 40t compensated with cleverly angled armour and a distinctive chevron-shaped front hull design that effectively provided the equivalent protection of 90 mm armour. The strategic use of lighter armour facilitated increased speed and manoeuvrability, paired with steel roller wheels and bulletproof tires powered by an 850 horsepower German Maybach engine, enabling the tank to reach speeds of 60 km/h. Although two prototypes were completed in 1952, the Lorraine 40t never entered production due to geopolitical shifts linked to the formation of NATO, France's integration into the alliance, and the supply of M47 Patton tanks by the US during the Korean War.

It was introduced in Update 1.75 "La Résistance". The Lorraine is one of the best representative of rank IV French medium tanks: it has good mobility, an oscillating turret (fitted with an autoloader), sloped armour in front and back, high hull, high gun placement, good gun depression, 4 crew member, a coaxial MAC 31 machine gun and large tracks. The Lorraine distinguishes itself by having a pike nose, similar to that of an IS-3, road wheels instead of metal ones and it is the first French vehicle to be able to consistently pierce more than 200 mm of armour at standard combat ranges and it can do it seven times a minute. This tank offers high top speed and acceleration, good turning rate (neutral steering) and awesome hill climbing capacity. Use its mobility to follow light tanks into large flanking manoeuvres, providing them an extra punch for scouted targets. In a more passive playstyle, its good reverse speed should get it fast enough into cover and out of bad situations if required.