Staff Writer (Updated: 7/12/2016):
As such, another solution to fulfill the requirement for a new heavy tank for the Red Army was sought. The multiple turret/multiple gun arrangement was akin to World War 1 tank design doctrine and a more modern design was now the call of the day. Regardless, Soviet design bureaus in 1938 still introduced multi-turreted tank designs for consideration, though most of these in prototype form ultimately settled on just two primary turrets.
One design bureau took the T-100 design as a starting point and her engineers devised a single turret heavy tank that was smaller dimensionally, lighter in weight while being better armored and mobile and sharing more mechanically with the new T-34 Medium Tank series. Formal construction of the new tank began in February 1940. The resulting design initiative became the "KV-1" and, like the T-100 before it, the prototypes were also put into combat against the Finns with better results, tested under real-world combat conditions. Whereas T-28 and T-35 tanks fell to Finnish tactics and ambushes, KV-1 tanks with their improved armor protection shines despite mechanical issues. The mechanical issues stemmed largely from the gearbox and clutch system. Incidentally, the KV-1 designation stemmed from Klimenti Voroshilov, the then-acting Soviet Defense Commissar (Defense Minister). The KV-1 was then formally accepted for serial production in the Red Army and immediately replaced the outmoded T-28 medium and T-35 heavy tanks - these being of 1935 origins while sporting a multi-turret arrangement and weighing over 44 tons. Despite the KV-1s mechanical issues, the growing need for more war tanks spurred serial production forward, resulting in some 5,219 examples completed by war's end. The Soviet Union was the sole operator of the KV-1 (aside from captured systems reconstituted by the German Army).
Upon inception into formal service with the Red Army, the KV-1 was considered the most powerful tank in the world based on the combination of firepower and weight and went on to lay the foundation for Soviet/Russian tanks for decades to come. It arrived in some number at a most crucial time for the Red Army for the German invasion of the Soviet Union through "Operation Barbarossa" in June of 1941 took the national forces by surprise. Only some 500 to 635 KV tanks were in service at the time of the invasion and these were initial used in spread out formations as opposed to dedicated armored regiments. It proved extremely useful in the break out role where it could use its stout armor configuration and high-powered main gun to smash through German defenses, leading the thrust of Red Army offensives and opening gaps for following T-34 Medium Tanks. As speed was not essential to the role, the KV-1 was more or less designed for such a feat. By 1942, the Soviets had learned that their KV tanks were much more effective in dedicated tank regiments and fielded them as such for the duration of the war. German crews were quick to note the new Soviet tank and were surprised to find their anti-tank weapons proving ineffective against the full frontal armor protection of KZ-1s, forcing infantry squads to tackle tanks head-on by any means necessary. Even the fabled "88" artillery guns required some work against tackling KV-1 tanks head-on. It was only the arrival of the German Panther and Tiger I tanks that more or less unseated the KV-1 series.
Externally, the immense KV-1 showcased a most stout design. Her appearance was characterized by her track systems, each side fitted with six road wheels, three track return rollers, a rear-set drive sprocket and forward-set track idler. The hull sported a heavily-sloped glacis plate leading up to a shallow hull superstructure to which was mounted a heavy turret system along a circular bustle. The main armament was fitted to the turret backed by a collection of light machine guns throughout the design. The engine was held in a rear compartment. The KV-1 in all its variant forms was crewed by five personnel made up of the driver (seated front center in the hull), a bow gunner (front left hull), tank commander, gunner and dedicated machine gunner. A detrimental facet of the KV-1's internal design was that the commander doubled as the main gun loader, distracting him from critical goings-on on the battlefield.
Main armament of the KV-1 in 1942 was a 76.2mm main gun (originally L-11 series) fitted to the traversing turret. A 7.62mm DT general purpose machine gun was fitted next to the system in a coaxial mount. Another 7.62mm DT machine gun was added to the rear turret wall to counter enemy infantry attempting to advance upon the tank from the vulnerable rear areas. A third 7.62mm DT machine gun was manned at the front left hull of the design, intended as an anti-infantry defensive gun. Some KV-1 production models ultimately added a fourth 7.62mm DT machine gun at the commander's cupola for both anti-infantry usage and to counter the threat from low-flying strike aircraft.