The French had planned for a defensive war and built tanks accordingly; infantry tanks were designed to be heavily armoured. Within France and its colonies, roughly 5,800 tanks were available during the time of the German offensive, and some when they came into contact were effective against the German tanks.
The R 35 was intended to replace the FT as standard light infantry tank from the summer of 1936, but even by May 1940 not enough conscripts had been retrained and therefore eight battalions of the older tank had to be kept operational. On 1 September 1939, at the outbreak of war, 975 vehicles had been delivered out of 1070 produced; 765 were fielded by tank battalions in France. Of a total order for 2,300 at least 1,601 had been produced until 1 June 1940 serial numbers known to be actually used indicate a production of at least 1670 vehicles.
In the Battle of France, despite an advantage in number and armour against the Germans, the French tanks were not used to good enough effect. Ironically, cooperation with the infantry was poor. The Cavalry units alone were too few in number.
In armour and firepower, French tanks were generally not inferior to their German counterparts. In one incident, a single Char B1 "Eure" was able to destroy thirteen German tanks within a few minutes in Stonne on 16 May 1940, all of them Panzer III and Panzer IV tanks.
The 37mm and 20mm guns the Germans used were ineffective at penetrating the thick armour of the B1, which was able to return safely despite being hit a large number of times. Even German General Rommel was surprised at how the French tanks withstood the German tank shells and had to resort to using the German 88 artillery as antitank guns against the French tanks to knock them out.
Setbacks the French military suffered were more related to strategy, tactics and organisation than technology and design. Almost 80 percent of French tanks did not have radios, since the battle doctrine employed by the French military was more a slow-paced, deliberate conformance to planned maneuvers. French tank warfare was severely restricted as tanks were assigned to infantry divisions, and were intended to provide support for infantry. Unlike Germany, which had dedicated tank divisions, France did not separate tanks from the infantry, and were unable to respond quickly to the Blitzkrieg tactics employed by the Germans, which involved rapid movement, mission-type orders and combined-arms tactics.
The S35 medium tank entered service in January 1936 with the 4e Cuirassiers. At the end of 1937 the SA 35 gun became available and deliveries of the main production series could begin. By mid 1938 a hundred had been produced, 270 on 1 September 1939 and 246 delivered. On this date 191 served with the troops, 51 were in depot and four had been sent back to the factory for overhaul. After the outbreak of war a fourth order of 200 was made, bringing the ordered total to 700. Later it was decided that from the 451st vehicle onward the tanks would be of the improved S 40 type. Production in fact totalled 430 by June 1940, including the prototype and the preseries.
Of these about 288 were in front-line service at the beginning of the Battle of France, with the three armoured divisions of the Cavalry, the Divisions Légères Mécaniques or Mechanised Light Divisions ("light" here meaning "mobile"). Each of these had an organic strength of eight squadrons with ten S35s; each squadron however had a matériel reserve of two tanks and regimental and brigade commanders in practice had personal tanks too, resulting in a total of 88 vehicles per division. Furthermore, 31 were present in the general matériel reserve, 49 in factory stocks and 26 were being processed for acceptance.
These vehicles were later issued to several ad hoc units, such as the 4th DCR (commanded by Charles de Gaulle) which received 39, part of 3e Cuirassiers, the 4th DLM (10), and some Corps-francs Motorisés (about 25). Also the destroyed 1st, 2nd and 3rd DLM were reconstituted with a small number of tanks, the first two divisions received ten S 35s, the third twenty; S 35s further served with the 7e Cuirassiers (25) and a platoon of three was present in the 3e RAM of the 3e DLC.
In May 1940 during the Battle of France the DLMs were tasked with the difficult manoevre of carrying out a quick advance into the Low Countries, followed by a holding action to allow the infantry divisions following behind to dig themselves in. The 2nd and 3rd DLM were concentrated in the Gembloux gap between Louvain and Namur, where there were no natural obstacles to impede a German advance. They had to spread out somewhat to hold that sector against incursions by the German 3rd and 4th Panzer Divisions. This was necessitated by the local tactical situation and did not reflect some fundamental difference in doctrine between the use of the DLMs and the Panzerdivisionen.
Both types of units were very similar in equipment, training and organisation, as the German armoured divisions too were primarily intended for strategic exploitation, while the breakthrough phase was preferably left to the infantry. The resulting tank battle from 13 to 15 May, the Battle of Hannut, was with about 1700 AFVs participating the largest until that day and is still one of the largest of all time. The S 35s gave a good account of themselves, proving to be indeed superior to the German tanks in direct combat, but they were rather hesitantly deployed as the French High Command mistakenly supposed the gap was the German Schwerpunkt and tried to preserve their best tanks to block subsequent attacks by the rest of the Panzerwaffe.
When it transpired the attack was really a feint and the forces in the north were in danger of being cut off by the German advance south of Namur, the 1st DLM that had very quickly moved 200 kilometres to the north to help the Dutch, was hurriedly rushed south again. The resulting disorder and breakdown of most of its S 35s rendered this unit, the most powerful of all Allied divisions, impotent; it was defeated by the German 5th Panzerdivision on 17 May. The other DLMs fought a delaying battle, participated in the Battle of Arras and then disintegrated. Committing its only strategically mobile armour reserve early in the battle had made the French Army fatally vulnerable to a German strategic surprise.
After the June 1940 armistice, S 35s were allowed to be sent to West Africa to bolster the hold of the Vichy regime on that region. They were issued to the 12e régiment de Chasseurs d'Afrique that, after French forces in Africa had sided with the Allies, operated them against German and Italian forces during the Tunisia Campaign. After the liberation of France in 1944 an armoured unit was raised, the 13e Régiment de Dragons, using French matériel, among which were seventeen S 35s.
After the fall of France a number of S 35s (297 were captured according to some sources) were taken into service with the Wehrmacht as the Panzerkampfwagen 35-S 739(f). The Germans modified the cupola by cutting its top off and installing a simple hatch.
The 21st and 25. Panzerdivision in 1943 used some S 35s when reforming after having been largely destroyed. Some of these units fought in Normandy in 1944, and there were still twelve S 35s listed as in German service on 30 December 1944.