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Heavy Tanks

year	name	tons	gun	built
19_	IS Tank Series	..	mm
19_	Object 277	..	mm
19_	Object 278	..	mm
19_	Object 279	..	mm
19_	Object 432	..	mm
19_	Object 757	..	mm
19_	Object 770	..	mm

From the first to the last day of the war, Soviet heavy tanks terrified the enemy. On June 22, 1941 the best heavy tank in the world was the KV-1, and on May 9, 1945 - the IS-3 *. We see these tanks on pedestals, in museums and in cinema. Post-war heavy tanks are hardly known to the general reader. They were created in an atmosphere of utter secrecy, were not exported abroad, did not participate in local wars, and by the 1990s they had been completely forgotten.

What is a heavy tank? In NATO countries, a tank with a heavy gun of 120 mm caliber or more was considered heavy. In the USSR, tanks were classified by their combat weight, and combat vehicles weighing over 40 tons were considered heavy. Thus, according to our classification, such western medium tanks as, for example, M26, M46, M47, M60 (USA) or Centurion and Chieftain (England) should be classified as heavy tanks. The modern main NATO tanks have exceeded the 55-ton milestone: (M1A1 - 57.1 tons; Leopard-2A4 - 55.2 tons; Challenger - 62 tons).

In the immediate post-war years, the evolution of Soviet heavy tanks proceeded in a very different fashion from heavy tank development in NATO. In the US Army, production of the M-4A3 medium tank was halted, and the M-26 Pershing tank became the forerunner of future main battle tanks. Likewise in Britain, the Centurion tank continued in production as the main battle tank, and tanks like the Churchill infantry tank and Cromwell cruiser tank simply disappeared. In both cases, this was a reaction to the German Panther tank, which set the benchmark for late the Great Patriotic War tank development.

The Soviet Union maintained the medium tank/heavy tank distinction much later than any other major army, and this had significant impact of the nature of its main battle tank design. Current Russian main tanks such as the T-64, T-72, and T-80 have all evolved out of medium tank designs and have tended to be much lighter and smaller than their American and British counterparts, which evolved out of World War 2's definition of heavy tanks. At the conclusion of the Great Patriotic War, the Soviet Union had two heavy tanks in production, the IS-2M and the IS-3. Both shared a common powertrain and armament system; the principal difference was in the hull and turret castings with the IS-3 embodying the latest trends in Soviet design. As a result, the IS-3 replaced the IS-2M at the sole production facility at the Chelyabinsk Tractor Plant Number 100 (Tankograd) by late 1945.

No significant number of IS-3s were ready before the end of the war in Europe, and the IS-3 was first publicly displayed at a victory parade in Berlin on 7 September 1945. The hull and turret configuration of the IS-3 were enormously influential for their sleek simplicity. In the Soviet Union, the simple hemispherical shape was later adopted on subsequent Soviet medium tanks such as the T-54A and made was the standard until today's T-72B and T-80. In the West, the shape influenced designs such as the American M-48, German Leopard-1 and French AMX-30. Although influential overseas, the IS-3 had a troubled career in the post-war Soviet Army.

The IS-3 design had been pushed into production much too quickly. Large numbers of IS-3 tanks were sidelined with mechanical problems. The thick armor plates on the front of the hull proved worrisome as the welds tended to crack open after service use, probably from the vibration of rough cross-country travel and the shock of gun firing. From 1948 to 1952, a redesign effort was undertaken to correct the problems. This included strengthening the hull, improving the final drive and reinforcing the engine mounts. Production of the IS-3 at Chelyabinsk lasted until 1951 by which time about 1,800 had been manufactured.

Both Britain and the United States did build heavy tanks in the 1950s, namely the 120mm armed Conqueror and the M103. In both cases these were overreactions to the Soviet T-10 heavy tank, and only a few hundred of each type were built, compared with several thousand Soviet heavy tanks.

Troyanov began work to further evolve of the IS-2 design under the code name Obiekt 701. Several alternatives were proposed on paper, and three designs were presented to the Red underway in 1944, the design team under Army's GBTU tank directorate: the Obiekt 701-2, armed with the S-34 100mm gun, the Obiekt 701-5 with a different armor configuration, and the Obiekt 701-6 armed with the standard D-25T 122mm gun. The latter was accepted for further development.

There were three significant changes in the Obiekt 701-6 design: thicker armor, a lengthened hull, and an uprated engine. The armor basis for the hull was increased to 160 millimeter and the turret to 250 millimeter. The 750 horsepower V-12 engine used a revised cooling system influenced by the layout of German Panther tanks, with the radiators under a pair of circular fans. The design was accepted for quantity production as the IS-4 tank in 1947.

The IS-4 tank was mass-produced from 1947 to 1949. In total, about 200-250 were manufactured. After a short production run, IS-4 production was halted. Most of these tanks served in the Far East, including in Manchuria, where they were ready to strike at the American troops invading Korea. The main criticism was that the speed and the mobility of the vehicle were inadequate. In November 1950 after the outbreak of the Korean War, nearly all of the IS-4 regiments were shipped to the Far East. They were deployed to form the shock force for a tank army that Stalin was organizing to intervene in the Korean conflict. In spite of intense pressure from the Chinese, Stalin decided against intervening in Korea for fear it would result in the outbreak of a general war with the nuclear-armed American armed forces. The IS-4s remained in the region and in the late 1950s, they were modernized along the same lines as the IS-3M and kept in service into the 1960s.

There have been repeated reports that several superheavy tanks were under development in the Soviet Union in 1945, including a 150-ton tank. None of these designs appear to have progressed beyond paper studies, however, or they remain so secret that they still are not discussed today. Among these designs were reputed to be the Vladimir Lenin VL-1, fitted with a front mounted engine and rear mounted turret.

Due to the significant existing inventories of heavy tanks, both the IS-2M and IS-3 underwent modernization programs in the post-war years. In 1954, the IS-2s began to be rebuilt as the IS-2M. This program included an increase in the amount of main gun ammunition from 28 to 35 rounds, an improved driver's periscope, the improved V-54K-IS engine, a modernized engine cooling and oil flow system, new radios and intercoms. Externally, the IS-2M had stowage increased by adding tool bins on the front hull side; dust skirts were also added.

The parallel program for the IS-3M began in 1960 and included additional hull reinforcement, replacement of the DShK 12.7mm machine gun with the DShKM, addition of a TVN-2 night vision device for the driver, substitution of the V-54K-IS engine, incorporation of the Multitsiklon air filter system and many other small changes. New wheels were added from the T-10 heavy tank which, had improved ball-bearings. In addition, external stowage was improved and dust skirts were added over the suspension.

In the postwar Soviet Army, heavy tanks were deployed much like the World War 2 pattern. They were deployed in independent tank regiments (21 tanks) or independent heavy tanks brigades (65 tanks) under army control and could be allotted to provide long-range fire support for tank divisions. During the 1947 reorganization, a special heavy armored regiment was added to the tank and mechanized divisions, containing 44 to 46 heavy tanks and 21 of the related ISU-122 or ISU-152 assault guns.

This formation was added due to Soviet recognition that the standard Soviet tank regiments, still primarily equipped with the T-34-85, could not deal with the newer British or American tanks like the M-26 Pershing or the Centurion. This deployment pattern remained in effect until the major reorganizations of 1958 through 1959.