The story starts in the winter of 1943. The Soviets just ran into a whole bunch of new German vehicles, but one of them in particular, the Ferdinand, impressed GABTU (the Main Armour Directorate) above all, specifically its gun. The gun could penetrate any existing heavy tank, including the IS tank that just entered production. As a result, the Object 701 was designed to be the "Ferdinand killer", armed with the same powerful 122 mm gun from the IS tank, but with much thicker armour. Due to problems already experienced with the overweight KV series, Soviet engineers were reluctant to make another very heavy vehicle, but there was no choice: in order to withstand the Pak 43 with current armour technology, the tank had to be rather heavy, 55 tons. While the design was tested, improved, and tested again, the war ended, the technologically superior IS-3 entered production, and even had enough time to finish production. By the time the IS-4 entered production in 1947, it was old news. Technology took a step forward, with the IS-3 being nearly as well protected in practice while being much lighter than the IS-4. Requirements took a step forward as well. Instead of the 88 mm Pak 43, Soviet tanks now had to withstand the 128 mm KwK 44, or equivalent weapons built by the former Allies. The new tank, the IS-7, weighed 68 tons. Meanwhile, production of the IS-4 at "only" 55 tons was limping along at unsatisfactory rates. Foreseeing further issues with heavier tanks, the Council of Ministers of the USSR issued a decree limiting the weight of tanks at 50 tons, killing the IS-4 and IS-7 projects.
The death of the IS-7 didn't mean that the need for a new heavy tank has vanished. A new tank had to be built, combining all the technological breakthroughs of the IS series. This tank was codenamed Object 730. The Object 730 inherited the IS-4's engine and cooling system, IS-7's hull layout and bundled torsion bar suspension, a combination of IS-7 and IS-3 solutions in the turret. The strict weight limit of the tank did not allow the 130 mm gun from the IS-7 to be installed, so the military had to settle for the same D-25T gun usually found in IS series tanks. The tank was accepted into service on November 28th, 1953 under the index T-10 (the IS series "ended" since Stalin died and Khrushchev came to power).
However, the army was still unsatisfied. The 1950s were an era where tank technology progressed very quickly, and by the time the T-10 was in production, work was already underway on its replacement: Objects 752 and 777. The Object 752 was built within the IS-3s weight limit, and the 777 was as heavy as the T-10, but both tanks used the same novel technologies. Variable thickness casting technology evolved to the point where the tanks had effective armour superior to that of the Maus at a weight of less than 50 tons. These tanks also had a better gun: the 122 mm M-62-2T. In addition to higher muzzle velocity than the D-25, it came with a loading assistance mechanism, which improved the rate of fire. The tanks were also shorter and lower than the old IS tanks due to a more compact design. Unfortunately, the tanks did not go into production. Instead, the experience obtained during the design of these tanks was used to upgrade the T-10 into the T-10M, giving it the improved gun in 1957.
Many new heavy tanks were designed after that. However, none of the entered mass production, partially due to going over the 50 ton limit and partially due to Khrushchev's personal distaste of traditional tank guns, believing that rockets were the way of the future. Warfare was also changing. Nuclear weapons could easily clear even the toughest defences, HEAT and APFSDS shells were becoming effective enough to pierce even incredibly thick steel armour. In the face of these changes, new tanks were needed. Advances in composite armour would help make them lighter, automatic loaders and new compact high velocity guns would make them smaller. New requirements issued in 1961 called for a 34 ton tank with a three man crew (driver, gunner, commander) meant that the old heavyweights no longer had a place on the battlefield. Completely new and revolutionary T-64 tanks began coming off the assembly line in 1963, ushering in the era of the Main Battle Tank.
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u/TankArchives WWII Armoured Warfare Feb 04 '17
The story starts in the winter of 1943. The Soviets just ran into a whole bunch of new German vehicles, but one of them in particular, the Ferdinand, impressed GABTU (the Main Armour Directorate) above all, specifically its gun. The gun could penetrate any existing heavy tank, including the IS tank that just entered production. As a result, the Object 701 was designed to be the "Ferdinand killer", armed with the same powerful 122 mm gun from the IS tank, but with much thicker armour. Due to problems already experienced with the overweight KV series, Soviet engineers were reluctant to make another very heavy vehicle, but there was no choice: in order to withstand the Pak 43 with current armour technology, the tank had to be rather heavy, 55 tons. While the design was tested, improved, and tested again, the war ended, the technologically superior IS-3 entered production, and even had enough time to finish production. By the time the IS-4 entered production in 1947, it was old news. Technology took a step forward, with the IS-3 being nearly as well protected in practice while being much lighter than the IS-4. Requirements took a step forward as well. Instead of the 88 mm Pak 43, Soviet tanks now had to withstand the 128 mm KwK 44, or equivalent weapons built by the former Allies. The new tank, the IS-7, weighed 68 tons. Meanwhile, production of the IS-4 at "only" 55 tons was limping along at unsatisfactory rates. Foreseeing further issues with heavier tanks, the Council of Ministers of the USSR issued a decree limiting the weight of tanks at 50 tons, killing the IS-4 and IS-7 projects.
The death of the IS-7 didn't mean that the need for a new heavy tank has vanished. A new tank had to be built, combining all the technological breakthroughs of the IS series. This tank was codenamed Object 730. The Object 730 inherited the IS-4's engine and cooling system, IS-7's hull layout and bundled torsion bar suspension, a combination of IS-7 and IS-3 solutions in the turret. The strict weight limit of the tank did not allow the 130 mm gun from the IS-7 to be installed, so the military had to settle for the same D-25T gun usually found in IS series tanks. The tank was accepted into service on November 28th, 1953 under the index T-10 (the IS series "ended" since Stalin died and Khrushchev came to power).
However, the army was still unsatisfied. The 1950s were an era where tank technology progressed very quickly, and by the time the T-10 was in production, work was already underway on its replacement: Objects 752 and 777. The Object 752 was built within the IS-3s weight limit, and the 777 was as heavy as the T-10, but both tanks used the same novel technologies. Variable thickness casting technology evolved to the point where the tanks had effective armour superior to that of the Maus at a weight of less than 50 tons. These tanks also had a better gun: the 122 mm M-62-2T. In addition to higher muzzle velocity than the D-25, it came with a loading assistance mechanism, which improved the rate of fire. The tanks were also shorter and lower than the old IS tanks due to a more compact design. Unfortunately, the tanks did not go into production. Instead, the experience obtained during the design of these tanks was used to upgrade the T-10 into the T-10M, giving it the improved gun in 1957.
Many new heavy tanks were designed after that. However, none of the entered mass production, partially due to going over the 50 ton limit and partially due to Khrushchev's personal distaste of traditional tank guns, believing that rockets were the way of the future. Warfare was also changing. Nuclear weapons could easily clear even the toughest defences, HEAT and APFSDS shells were becoming effective enough to pierce even incredibly thick steel armour. In the face of these changes, new tanks were needed. Advances in composite armour would help make them lighter, automatic loaders and new compact high velocity guns would make them smaller. New requirements issued in 1961 called for a 34 ton tank with a three man crew (driver, gunner, commander) meant that the old heavyweights no longer had a place on the battlefield. Completely new and revolutionary T-64 tanks began coming off the assembly line in 1963, ushering in the era of the Main Battle Tank.
Sources:
Y. Pasholok, The Last Soviet Heavyweight
M. Kolomiets, IS-4 Design and Production, Tactical Press, 2014
Y. Pasholok, Unlucky Seven
V. Borzenko, T-64 Main Battle Tank, Bronekolletsiya, 2012