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 of the interwar period
Initially, the tanks and armored cars in Soviet hands were a mix of FT-17 imports and a few British tanks left behind in the civil war. The first Soviet tank, the T-18 (sometimes called MS-1) was a fairly close copy of the FT-17, but with improved suspension and a larger turret. Stalin's enthusiasm for industrialisation and mechanisation drove an aggressive military development program, resulting in by far the largest and broadest tank inventory of all nations by the late 1930s.