Heavy tanks were favored by both the Soviets and Germans in the fighting of World War 2 (1939-1945) and both countries made significant progress in bringing about various heavy-class designs to the battlefield. For the Soviets, the stellar "Josef Stalin" IS-2 series was made possible by battlefield experiences gained in operational use of the KV-1 series tanks during the early phases of the war. The stout KV-1 series was introduced in 1939 and fought on into 1945 with over 5,200 examples produced for service.
With the German invasion of the Soviet Union in June of 1941, and the disaster than befell Soviet armored corps in the aftermath, the Soviets were pressed to get all manner of fighting vehicles to the front. This desperation also lay the groundwork for a new type of heavy tank, one requested by Soviet Army authorities that provided the performance and operating weight of the T-34 Medium Tank with the armor and firepower effectiveness of the KV-1. For all its value, the KV-1 proved unreliable and its use in the Soviet ranks did not play up to its strengths. The new tank would succeed both the T-34 and KV-1 lines in service.
The KV-1 was used as the starting point for the new vehicle which emerged from the Experimental Tank Plant in Chelyabinsk. Engineers elected for cast armor in the construction of the tank wherever possible in an effort to reducing reliance on external armor plating and internal gaps. Angled faces were set about the shallow superstructure and the turret incorporated rounded edges for basic ballistics protection. Armor protection measured 120mm at the front bow of the hull and 85mm along the frontal turret face. The running gear was pulled from the T-34 tank though the roadwheels of the KV-1 were retained. Overall weight tipped the scales at 35 tons (short).
The prototype was arranged in short order and trials were already underway for May of 1942. Almost immediately there were mechanical issues and the track-and-wheel arrangement proved prone to failure. The death of the original project lead did little to help things as well. Engineers pursued the KV-13 design under a new director and began development and construction of two distinct KV-13 prototype offshoots, each with all-new turrets and only a few components carried over from the original offering. The two prototypes differed mainly in the main armament installed, the first to carry the 76mm ZiS 5 series gun and the second to field the 122mm U-11 howitzer. By this time, the arrival of the German "Tiger I" Heavy Tank (detailed elsewhere on this site) forced Soviet authorities to refocus interest in a new, modern dedicated heavy tank of their own instead of a universal super-medium tank.
Therefore both designs, emerging in 1943, served as prototypes for what became the IS-1 and IS-2 heavy tanks (respectively - each detailed elsewhere on this site). The idea of a super-medium combat tank never materialized and efforts were placed to brining more T-34 tanks online while also reinforcing these numbers with more dedicated heavy tanks. While only three KV-13 tanks were ever produced, they were priceless in ushering the development of the classic Soviet heavy tank lines that worked so well in the push towards Berlin in 1945.
As designed, the KV-13 showcased a length of 6.6 meters, a width of 2.8 meters and a height of 2.5 meters. Its crew numbered three personnel. Beyond the main armament was a 7.62mm DT-29 series machine gun in a coaxial mounting at the turret. Power was served through a V12 liquid-cooled diesel-fueled engine developing 600 horsepower coupled to a mechanical transmission system. The hull sat a torsion bar-sprung suspension system. The vehicle could make speeds of 40 miles per hour on paced roads and held an operational range out to 200 miles.