Heavy tank
The Char 2C was one of the largest tanks ever produced. At the start of World War II, France and the Soviet Union were the only countries to have inventories of heavy tanks, such as the Char B1, T-35, and KV-1. The Matilda II was designed under the British infantry tank concept which is similar to the heavy tank having thick armor and weighing more than their other tanks. It’s usually separate because they have less firepower with their cruiser tanks (comparable to mediums) at the time having the same main armament but more machine guns. Later war examples were the German Tiger I and II, as well as the Soviet IS series. Note that "heavy" versus "medium" is more a question of tactical roles than weight; the Panther, for example, was a "medium" tank that outweighed most Allied "heavy" tanks.
Tanks in France
But industrial initiative also led to swift advances. The car industry, already used to vehicle mass production and having much more experience in vehicle layout, in 1916 designed the first practical light tanks, a class largely neglected by the British. It would be Renault's excellent small tank design, the FT, incorporating a proper climbing face for the tracks, that was the first tank to incorporate a top-mounted turret with a full 360° traverse capability. In fact the FT was in many respects the first truly 'modern' tank having a layout that has been followed by almost all designs ever since: driver at the front; main armament in a fully rotating turret on top; engine at the rear. Previous models had been "box tanks", with a single crowded space combining the role of engine room, fighting compartment, ammunition stock and driver's cabin. (A very similar Peugeot prototype, with a fixed casemate mounting a short 75mm cannon, was trialled in 1918 but the idea was not pursued) The FT would have the largest production run of any tank of the war, with over 3700 built, more numerous than all British tanks combined. That this would happen was at first far from certain; some in the French army lobbied for the alternative mass production of super-heavy tanks. Much design effort was put in this line of development resulting in the gigantic Char 2C, the most complex and technologically advanced tank of its day. Its very complexity ensured it being produced too late to participate in World War I and in the very small number of just ten, but it would be the first tank with a three-man turret; the heaviest to enter service until late in World War II and still the largest ever operational.