KV-13

The KV-13 (Russian: KB-13) was an experimental Soviet medium tank created during World War II. It was developed on the KV-1 chassis in the SKB-2 design bureau of the Chelyabinsk Kirov Plant in late 1941 – early 1942, as a "universal" tank, intended to replace the production of T-34 medium tanks and KV-1 heavy tanks at the same time.

Development
The first prototype of the KV-13 was made in the spring of 1942, but in the fall of that year tests showed a lack of mechanical reliability and demonstrated the need to strengthen the vehicle's armour and to equip it with the new three-seat turret. While production of two modified prototypes incorporating these modifications began in December 1942, work on the KV-13 as a medium tank was discontinued in favour of continuing the production of the T-34. The further development of the project using two modified KV-13 prototypes led to the creation in 1943 of the IS-1 heavy tank. This tank was never used in combat.