In the early 1930s the calvary issued specifications for a Automitrailleuse de Combat (AMC). It was built by a Schneider subsidiary called Société d'Outillage Mécanique et d'Usinage d'Artillerie (SOMUA) at Saint Ouen. It was initially called the AMC SOMUA AC-3 but it was decided to make it the standard medium tank of the French army and was then designated the Char S-35. S being short for SOMUA and 35 the year of it's introduction.
It entered service in 1936 and by June 1940, around 500 had been produced. When Germany invaded about 250 were in front-line service.
A double differential system was used for steering. There were two assemblies of four bogie wheels mounted in pairs on articulated arms that were controlled by semi-elliptic leaf springs. One bogie wheel was mounted independently in the rear on a coil spring. The wheels were made of steel, with rims that ran in a groove in the tracks. Two return rollers also ran in the grooves.
The engine was on the left in the rear and a self-sealing gas tank on the right. The idler was located in front and the drive sprocket in the rear.
The S-35 was made from a cast turret and hull.
One fault that was discovered during combat was that the upper and lower hull halves were joined by a ring of bolts, if an anti-tank round hit the seem it could split apart the hull.
There were three cast sections that were bolted together. The lower section stretched the full length, with the engine, transmission, controls and suspension were mounted. The other armored sections were then bolted to the top rim of the lower section. The rear section covering the engine and transmission. There was a fireproof bulkhead separating the fighting compartment from the engine. The front section covered the fighting compartment and held the turret.
The turret was electrically traversed. The turret only had room for the commander which hampered it in fighting against the Germans. The turret was identical to the one used on the Char B1-bis and the D2. The commander sat on a saddle in the APX 4 turret, which rotated around a pole mounted in the floor.
The driver was located on the left of the hull and had a hatch that was in front of him which was usually left open when the tank moved behind the lines. The radio operator sat on the right. The normal way to enter and exit the tank for the driver and radio operator was through a door on the left side of the hull. There was also a floor escape hatch.
There were supposed to be two radios installed. There was a shortage of radios and about 80% of the S-35s did not have them.
The 47 mm L/34 had a muzzle velocity of 2,200'/sec. The 47 mm AP shell weighed 3.8 lbs and had a muzzle velocity of 2,805'/sec.