After disappointing results with the multi-turreted
T-35 heavy tank, Soviet tank designers started drawing up replacements. The T-35 conformed to the 1920s notion of a "breakthrough tank" with very heavy firepower though its armour protection was lacking and it suffered from poor mobility. The
Spanish Civil War demonstrated the need for much heavier armour on tanks, and was the main influence on Soviet tank design just prior to World War II. Several competing designs were offered, and even more were drawn up prior to reaching prototype stage. All had heavy armour,
torsion-bar suspension, wide tracks, and were of welded and cast construction. One of the main competing designs was the
SMK, which in its final form had two turrets, mounting one 76.2 mm and one 45 mm weapon. The designers of the SMK independently drew up a single-turreted variant and this received approval at the highest level. Two of these, named after the
People's Commissar for Defence, were ordered alongside a single SMK. The smaller hull and single turret enabled the designer to install heavy frontal and turret armour while keeping the weight within manageable limits. The KV was ordered right off the drawing board. When the Soviets entered the
Winter War, the SMK, KV and a third design, the
T-100, were sent to be tested in combat conditions. The KV outperformed the SMK and T-100 designs. The KV's heavy armour proved highly resistant to
Finnish anti-tank weapons, making it more difficult to stop. In 1939, the production of 50 KVs was ordered. During the war, the Soviets found it difficult to deal with the concrete bunkers used by the Finns and a request was made for a tank with a large howitzer. One of the rush projects to meet the request was to put the howitzer in a new turret on one of the KV tanks. Initially known as 'Malen'kaya Bashenka' (little turret) and 'Bol'shaya Bashnya' (big turret), the 76-mm-armed tank was redesignated as the
KV-1 heavy tank and the 152 mm
howitzer one as
KV-2 heavy artillery tank. KV tanks first faced the Germans in the
Battle of Raseiniai, just after the start of
Operation Barbarossa. On 23 June, over 200 German tanks advancing through Lithuania encountered Soviet armor including KV-1 and KV-2 tanks. Although the KVs' frontal armor was sufficient to deflect anti-tank fire, German troops were able to outflank them and destroy them with explosive charges or lure them to within point-blank range of direct-fire artillery. Of the more than 200 Soviet tanks lost at Raseiniai, 29 were KVs. "was the main stumbling block of the KV-1, and there was some truth to rumors of Soviet drivers having to shift gears with a hand sledge"; The KV outweighed most other tanks of the era, being about twice as heavy as the heaviest German tank at that time (before the
Tiger). As
appliqué armour and other improvements were added without increasing engine power, later models were less capable of keeping up to speed with medium tanks and had more trouble with difficult terrain. In addition, its firepower was no better than that of the
T-34. The KV-1's 76.2 mm gun also came in for criticism. While adequate against all German tanks, it was the same gun as carried by smaller, faster, and cheaper T-34 medium tanks. In 1943, it was determined that this gun could not easily penetrate the frontal armour of the new Tiger, the first German heavy tank, one of which was captured near
Leningrad. The KV-1 was also much more difficult to manufacture and thus more expensive than the T-34, its advantages no longer outweighed its drawbacks. in Parola Because of its initial superior performance, the KV-1 was chosen as one of the few tanks to continue being built following the Soviet reorganization of tank production. Due to the new standardization, it shared a similar engine and gun as the T-34 (the KV used a 600 hp V-2K modification of the T-34's V-2 diesel engine, and had a ZiS-5 main gun while the T-34 had a similar F-34 main gun), was built in large quantities and received frequent upgrades. When production shifted to the "
Tankograd" complex in the
Ural Mountains, the KV-2 was dropped. While impressive on paper, it had been designed as a slow-moving bunker-buster. It was less useful in the highly mobile, fluid warfare that developed in World War II. The turret was so heavy it was difficult to traverse on uneven terrain. Finally, it was expensive to produce. Only about 210 KV-2s were made, all in 1940–1941, making it one of the rarest Soviet tanks. The KV-1 continued to get more armor to compensate for the increasing effectiveness of German weapons. This culminated in the
KV-1 model 1942 (German designation KV-1C), which had very heavy armor but lacked a corresponding improvement to the engine. It now weighed about 52 tons. Tankers complained that, although they were well-protected, their mobility was poor and they had no firepower advantage over the T-34 medium tank.
KV-1S In response to criticisms, the lighter
KV-1S was developed with thinner armor and a smaller, lower turret in order to reclaim some speed. The KV-1S had a commander's cupola with all-around vision blocks. It also had a sophisticated
planetary transmission that significantly increased the reliability, and allowed use of more efficient regenerative geared steering, unlike the solely clutch and brake steering systems used by the
Panzer III,
IV and T-34 and previous KV tanks. Its reduced weight allowed it to achieve a top speed of 43.3 km/h. Over 1,300 were built before production ended in August 1943. Although the KV-1S was, according to some, the best of the KV tanks, overcoming its predecessors' problems (at a cost of losing the heavy armor that made the earlier tanks so valuable, making it more of a slow medium tank than a heavy tank), more modern tanks were already in sight. Up-arming the regular turret of the KV-1S with an 85 mm S-31 resulted in the KV-1S-85. This was rejected as it came with the unacceptable loss of a dedicated commander, reducing the turret crew to two (unlike the 3-man turret fitted to the T-34/85). However, the thinning-out of the armor called into question why the tank was being produced at all, when the T-34 could seemingly do everything the KV could do and much more cheaply. The Soviet heavy tank program was close to cancellation in mid-1943. The appearance of the German
Panther tank in the summer of 1943 persuaded the Red Army to make a serious upgrade of its tank force for the first time since 1941. Soviet tanks needed bigger guns to take on the growing numbers of Panthers and the few Tigers.
KV-85 A stopgap upgrade to the KV series was the short-lived
KV-85 or
Objekt 239. This was a KV-1S with the new turret from the
Object 237 (IS-85) still in development, mounting the same 85 mm
D-5T gun as the
SU-85 and early versions of the T-34-85 (not yet in production at the time). The 85 mm proved capable of penetrating the
Tiger I from 1000 m and the demand for it slowed production of the KV-85 tremendously, only 148 were built between August and October 1943. Soviet industry was therefore able to produce a heavy tank as well armed as the
Tiger I before the end of 1943. Although the KV-85 was an excellent opponent to the Tigers and Panthers, it was a stopgap and thus was built in small numbers. and the HE shell would easily blow off the drive sprocket and tread of the heaviest German tank or
self-propelled gun. The IS-122 replaced the IS-85, and began mass production as the IS-2. The 85 mm gun saw service in the lighter SU-85 and T-34-85. == Variants ==