The Renault FT was widely used by French forces in 1918 and by the American Expeditionary Forces (AEF) in France in the later stages of World War I.
The battlefield debut of the Renault FT occurred on 31 May 1918 east of the Forest of Retz, near Chaudun, between Soissons and Villers-Cotterets, during the Second Battle of the Marne. This engagement, with 30 FTs, successfully broke up a German advance, but in the absence of infantry support, the vehicles later withdrew. From then on, gradually increasing numbers of FTs were deployed, together with smaller numbers of the older Schneider CA1 and Saint-Chamond tanks. As the war had become a war of movement during the summer of 1918, the lighter FTs were often transported on heavy trucks and special trailers rather than by rail on flat cars. Estienne had initially proposed to overwhelm the enemy defences using a "swarm" of light tanks, a tactic that was eventually successfully implemented. Beginning in late 1917, the Entente allies were attempting to outproduce the Central Powers in all respects, including artillery, tanks, and chemical weapons. Consequently a goal was set of manufacturing 12,260 Renault FT tanks (including 4,440 of the US version) before the end of 1919.
After the end of World War I, Renault FTs were exported to many countries (Belgium, Brazil, Czechoslovakia, Estonia, Finland, Iran, Japan, Lithuania, Netherlands, Poland, Romania, Spain, Switzerland, Turkey, and Yugoslavia). Renault FT tanks were used by most nations having armoured forces, generally as their prominent tank type. The tanks were used in many later conflicts, such as the Russian Civil War, Polish-Soviet War, Chinese Civil War, Rif War, Spanish Civil War, and Estonian War of Independence.
Renault FT tanks were also fielded in limited numbers during World War II, in Poland, Finland, France, and the Kingdom of Yugoslavia, although they were already obsolete. In 1940 the French Army still had eight battalions equipped with 63 FTs each and three independent companies with ten each, for a total organic strength of 534, all equipped with machine guns. These were put to use after most of the modern equipment was lost in earlier battles.
Many smaller units assembled after the start of World War II also used the Renault FT. This usage gave rise to the popular myth that the French had no modern equipment at all; in fact, they had more modern tanks than the Germans. The French suffered from tactical and strategic weaknesses rather than from equipment deficiencies. When the best French units were cut off by the German drive to the English Channel, the complete French materiel reserve was sent to the front as an expediency measure; this included 575 FTs. Earlier, 115 sections of FTs had been formed for airbase defence. The Wehrmacht captured 1,704 FTs. They used about a hundred for airfield defence and about 650 for patrolling occupied Europe. Some were used by the Germans in 1944 for street-fighting in Paris, but by this time they were hopelessly out of date. Vichy France used Renault FTs against Allied invasion forces during Operation Torch in Morocco and Algeria. The French tanks, however, were no match for the newly arrived American M4 Sherman and M3 Stuart tanks.
The FT was the ancestor of a long line of French tanks: the FT Kégresse, the NC1, the NC2, the Char D1, and the Char D2. The Italians produced the FIAT 3000, a moderately close copy of the FT, as their standard tank.
The Soviet Red Army captured fourteen burnt-out Renaults from White Russian forces and rebuilt them at the Krasnoye Sormovo Factory in 1920. Nearly fifteen exact copies, called "Russki Renoe", were produced in 1920–1922, but they never used in battle because of many technical problems. In 1928–1931 the first completely Soviet-designed tank was the T-18, a derivative of the Renault with sprung suspension.
In all, the Renault FT was used by Afghanistan, Belgium, Brazil, the Republic of China, Czechoslovakia, Estonia, Finland, France, Nazi Germany, Iran, Japan, Lithuania, the Netherlands, Philippine Commonwealth, Poland, Romania, the Russian White movement, the Soviet Union, Spain, Sweden, Switzerland, Turkey, the United Kingdom, the United States and the Kingdom of Yugoslavia.