IS tank family

The IS tank family  (IS in Cyrillic "ИС", meaning the Joseph Stalin or Iosif Stalin in Cyrillic "Ио́сиф Ста́лин") was a series of heavy tanks developed as a successor to the KV-series by the Soviet Union during World War II. It was named after Soviet leader Joseph Stalin.The heavy tank was designed with thick armour to counter the German 88 mm guns, and carried a main gun that was capable of defeating the German Tiger and Panther tanks. It was mainly a breakthrough tank, firing a heavy high-explosive shell that was useful against entrenchments and bunkers. The IS-2 was put into service in April 1944, and was used as a spearhead in the Battle of Berlin by the Red Army in the final stage of the war.

KV and IS-1
The KV series of Soviet heavy tanks was criticized by its crews for its poor mobility and lack of any heavier armament than the T-34 medium tank. In 1942 this problem was partially addressed by the lighter, faster KV-1S tank. The KV series were much more expensive than the T-34, without having greater combat performance; the heavy tank program was nearly cancelled by Stalin in 1943. However, the German employment of substantial numbers of Panther and Tiger tanks at the Battle of Kursk in 1943 changed Soviet priorities. In response, the Soviet tank industry created the stopgap KV-85, and embarked on the KV-13 design program to create a tank with more advanced armour layout and a more powerful main gun. The IS-85 (Object 237) prototype was initially accepted for production as the IS-1 heavy tank and first deliveries were made in October 1943. Production ended in January 1944.

Gun choice
Two candidate weapons were the A-19 122 mm gun and the BS-3 100 mm gun. The BS-3 had superior armour penetration (185 mm compared to 160 mm), but a less useful high explosive round. Also, the BS-3 was a relatively new weapon in short supply, while there was excess production capacity for the A-19 and its ammunition. Compared to the older 76.2 mm tank gun, the A-19 had very good armour penetration, similar to that of the effective 75 mm high velocity gun mounted on the German Panther, and delivered 3.5 times the kinetic energy of the older F-34.

After testing both BS-3 and A-19 guns, the latter was selected as the main armament of the new tank, primarily because of its ready availability and the effect of its large high-explosive shell when attacking German fortifications. The A-19 used a separate shell and powder charge, resulting in a lower rate of fire and reduced ammunition capacity, both serious disadvantages in tank-to-tank engagements. The gun was very powerful, and while its 122 mm armour-piercing shell had a lower muzzle velocity than similar late-issue German 75 mm and 88 mm guns, Soviet proving-ground tests established that the A-19 could penetrate the front armour of the German Panther tank, and it was therefore considered adequate in the anti-tank role.

German Army data on the penetration ranges of the 122 mm A-19 gun against the Panther tank showed it to be much less effective when the Panther stood at a side angle of 30 degrees to the incoming round: the A-19 gun was unable to penetrate the glacis plate of the Panther at any distance, and could only penetrate the bottom front plate of the hull at 100 m. It was the large HE shell the gun fired which was its main asset, proving highly useful and destructive in the anti-personnel role. The size of its gun continued to plague the IS-2, and the two-piece ammunition was difficult to handle and slow to reload (the rate of fire was only about two rounds per minute). Another limitation imposed by the size of its ammunition was the payload: only 28 rounds could be carried inside the tank.

Production
The IS-122 prototype replaced the IS-85, and began mass production as the IS-2. The 85 mm guns could be reserved for the new T-34-85 medium tank, and some of the IS-1s built were rearmed before leaving the factory, and issued as IS-2s.

The main production model was the IS-2, with the powerful A-19. It was slightly lighter and faster than the heaviest KV model 1942 tank, with thicker front armour and a much-improved turret design. The tank could carry thicker armour than the KV series, while remaining lighter, due to the better layout of the armour envelope. The KV's armour was less well-shaped and featured heavy armour even on the rear, while the IS series concentrated its armour at the front. The IS-2 weighed about the same as a German Panther and was lighter than the German heavy Tiger tank series, and was slightly lower than either.

Western observers tended to criticize Soviet tanks for their lack of finish and crude construction. The Soviets responded that it was warranted considering the need for wartime expediency and the typically short battlefield life of their tanks.

Early IS-2s can be identified by the 'stepped' front hull casting with its small, opening driver's visor. The early tanks lacked gun tube travel locks or antiaircraft machine guns, and had narrow mantlets.

Later improved IS-2s (model 1944) had a faster-loading version of the gun, the D25-T with a double-baffle muzzle brake and better fire-control. It also featured a simpler hull front without a 'step' in it (using a flat, sloping glacis armour plate). Some sources called it IS-2m, but it is distinct from the official Soviet designation IS-2M for a 1950s modernization. Other minor upgrades included the addition of a travel lock on the hull rear, wider mantlet, and, on very late models, an antiaircraft machine gun.

In the mid-1950s, the remaining IS-2 tanks (mostly model 1944 variants) were upgraded to keep them battle-worthy, producing the IS-2M, which introduced fittings such as external fuel tanks on the rear hull (the basic IS-2 had these only on the hull sides), stowage bins on both sides of the hull, and protective skirting along the top edges of the tracks.

IS-3


There are 2 tanks known as IS-3. IS-3 (Object 244) was an IS-2 rearmed with the long-barrelled 85mm cannon (D-5T-85-BM). It was developed by LKZ (in Leningrad) and was not taken in service. IS-3 (Object 703) was developed in late 1944 by ChTZ (in Chelyabinsk). This tank had an improved armour layout, and a hemispherical cast turret (resembling an overturned soup bowl) which became the hallmark of post-war Soviet tanks. While this low, hemispherical turret may have improved protection, it also significantly diminished the working headroom, especially for the loader (Soviet tanks in general are characterized by uncomfortably small interior space compared to Western tanks). The low turret also limited the maximum depression of the main gun, since the gun breech had little room inside the turret to pivot on its vertical axis. As a result, the IS-3 was less able to take advantage of hull-down positions than Western tanks. The IS-3's pointed prow earned it the nickname Shchuka (Pike) by its crews. It weighed slightly less and stood 30 cm lower than previous versions. Wartime production resulted in many mechanical problems and a hull weldline that had a tendency to crack open.

The IS-3 came too late to see action in World War II. The tank saw no action against the Germans, although one regiment was deployed against the Japanese in Manchuria.

Starting in 1960, the IS-3 was slightly modernized as the IS-3M, in a manner similar to the IS-2M.

IS-4
There are 2 different tanks known as IS-4. IS-4 (Object 245) was an IS-2 rearmed with a long 100mm D-10T cannon. It was projected by LKZ (in in parallel with IS-3 (Object 703) by the same design and development bureau, but was a heavier and better armoured vehicle. The hull was lengthened, with an extra set of road wheels added and an improved engine. Both the hull and turret was enhanced with increased armour. Several alternative armaments were explored in paper studies, although ultimately the IS-2's original 122mm gun was retained. An effort was also made to make use of technical data derived from study of the German wartime Panzer V Panther tank, which influenced the layout of the IS-4's engine cooling system. The tank was approved for mass production from 1947 to 1949 but due to disappointing speed and mobility only 250 were built. Most of these were transferred to the Russian Far East. In 1949, production was cancelled and later these tanks were removed from service.

IS-6
The IS-6 (Object 252) was an attempt to develop a practical electrical transmission system for heavy tanks. Similar systems had been tested previously in France and the United States and had been used with some success in the German Elefant/Ferdinand tank destroyer during World War II. The experimental transmission proved unreliable and was dangerously prone to overheating. Neither the transmission nor the IS-6 chassis itself were developed further.

IS-7
In 1948, the IS-7 heavy tank was developed. Weighing 68 metric tons, thickly armoured and armed with a 130 mm S-70 gun, it was the largest and heaviest tank ever tested by the USSR. Although it was in many ways an innovative design, it was never accepted for mass production due to its cumbersome size and the very impractical layout of its fighting compartment.

T-10
The IS-10 (also known as Objekt 730) was the final development of the KV and IS tank series. It was accepted into service in 1952 as the IS-10, but due to the political climate in the wake of Stalin's death in 1953, it was renamed T-10.

The biggest differences from its direct ancestor, the IS-3, were a longer hull, seven pairs of road wheels instead of six, a larger turret mounting a new gun with fume extractor, an improved diesel engine, and increased armour. General performance was similar, although the T-10 could carry more ammunition.

T-10s (like the earlier tanks they replaced) were deployed in independent tank regiments belonging to armies, and independent tank battalions belonging to divisions. These independent tank units could be attached to mechanized units, to support infantry operations and perform breakthroughs.

This was the last Soviet heavy tank to enter service. When the advanced T-64 MBT became available it replaced the T-10 in front line formations.

Operational history
The IS-2 tank first saw combat in early 1944. IS-2s were assigned to separate heavy tank regiments, normally of 21 tanks each. These regiments were used to reinforce the most important attack sectors during major offensive operations. Tactically, they were employed as breakthrough tanks. Their role was to support infantry in the assault, using their large guns to destroy bunkers, buildings, dug-in crew-served weapons, and other 'soft' targets. They were also capable of taking on any German AFVs if required. Once a breakthrough was achieved, lighter, more mobile T-34s would take over the exploitation.

The IS-3 first appeared to Western observers at the Allied Victory Parade in Berlin in September 1945. The IS-3 was an impressive development in the eyes of Western military observers, the British in particular, who responded with heavy tank designs of their own.

By the 1950s the emergence of the main battle tank concept&mdash;combining medium-tank mobility with the firepower and later armour of the heavy tank&mdash;had rendered heavy tanks obsolete in Soviet operational doctrine. In the late 1960s the remaining Soviet heavy tanks were transferred to Red Army reserve service and storage. The IS-2 Model 1944 remained in active service much longer in the armies of Cuba, China and North Korea. A regiment of Chinese IS-2s was available for use in the Korean War, but saw no service there. In response to border disputes between the Soviet Union and China, some Soviet IS-3s were dug in as fixed pillboxes along the Soviet-Chinese border. The IS-3 was used in the 1956 Soviet invasion of Hungary and the Prague Spring in 1968.

During the early 1950s all IS-3s were modernised as IS-3M models. The Egyptian Army acquired about 100 IS-3M tanks in all from the Soviet Union. During the Six Day War, a single regiment of IS-3M tanks was stationed with the Egyptian 7th Infantry Division at Rafah and the 125th Tank Brigade of the 6th Mechanized Division at Kuntilla was also equipped with about 60 IS-3M tanks. Israeli infantry and paratrooper units had considerable difficulty with the IS-3M when it was encountered due to its thick armour, which shrugged off hits from normal infantry anti-tank weapons such as the bazooka. Even the 90 mm AP shell fired by the main gun of the Israeli Defense Force (IDF) M48 Patton tanks could not penetrate the frontal armour of the IS-3s at normal battle ranges. There were a number of engagements between the M48A2 Pattons of the IDF 7th Armoured Brigade and IS-3s supporting Egyptian positions at Rafah in which several M48A2s were knocked out in the fighting. However, in one engagement between a battalion of IS-3s and 90MM-gun-armed M48A3's, 7 IS-3s were destroyed. The slow rate of fire, poor engine performance (the engine was not well suited to hot-climate operations), and rudimentary fire control of the IS-3s proved to be a significant handicap, and about 73 IS-3s were lost in the 1967 war. Most Egyptian IS-3 tanks were withdrawn from service, though at least one regiment of IS-3 tanks was retained in service as late as the 1973 October war. The IDF itself experimented with a few captured IS-3M tanks, but found them ill-suited to fast-moving desert tank warfare; those that were not scrapped were turned into stationary defensive pillbox emplacements in the Jordan River area.

After the Korean War, China attempted to reverse-engineer the IS-2/IS-3 as the Type 122 medium tank. The project was cancelled in favour of the Type 59, a copy of the Soviet T-54A.

Models

 * IS-85 (IS-1):1943 model armed with an 85 mm gun. When IS-2 production started, many were re-gunned with 122 mm guns before being issued.
 * IS-100:A prototype version armed with a 100 mm gun; it went into trials against the IS-122 which was armed with a 122 mm gun. Though the IS-100 was reported to have better anti-armour capabilities, the latter was chosen due to better all-around performance.
 * IS-122 (IS-2 model 1943):1943 model, armed with A-19 122 mm gun.
 * IS-2 model 1944 (sometimes "IS-2m"):1944 improvement with D25-T 122 mm gun, with faster-loading drop breech and new fire control, improved simpler hull front.
 * IS-2M: 1950s modernization of IS-2 tanks.
 * IS-3:1944 armour redesign, with new rounded turret, angular front hull casting, integrated stowage bins over the tracks. Internally similar to IS-2 model 1944, and produced concurrently. About 350 built during the war.
 * IS-3M: (1952) Modernized version of IS-3. Fitted with additional jettisonable external fuel tanks.
 * IS-4:1944 design, in competition against the IS-3. Longer hull and thicker armour than IS-2. About 250 were built, after the war.
 * IS-6:Prototype with an experimental electrical transmission. Chassis tested further with a conventional transmission after failure of the experimental system, but not deemed a significant enough improvement over existing heavy tank designs to warrant mass production.
 * IS-7:1946 prototype, only three built. The IS-7 model 1948 variant had a weight of 68 metric tons and it was armed with the 130 mm S-70 naval cannon (7020 mm long barrel) innovation is the incorporation of automatic loader can achieve up to 8 rounds per minute,stabilizers, infrared night scopes, 8 machine guns, armour from 220 to 300 mm thickness and 60 km/h roadspeed. Crew of five. The Slostin gun was to be installed as its AA armament.
 * IS-10: 1952 improvement with a longer hull, seven pairs of road wheels instead of six, a larger turret mounting a new gun with fume extractor, an improved diesel engine, and increased armour. Renamed T-10 as part of the Destalinisation of the Soviet Union in the 1950s.

Operators

 * 🇨🇳 China
 * People's Liberation Army: IS-2s operated during the Korean War and in concrete bunkers along the Sino-Soviet border.
 * 🇨🇺 Cuba
 * Cuban Army: 41 IS-2Ms delivered in 1960.
 * 🇪🇬 Egypt
 * Egyptian Army: Operated IS-3M from 1956-1967, some in use in 1973.
 * Nazi Germany
 * Wehrmacht: Captured one or two IS-2 in May 1945.
 * 🇮🇱 Israel
 * IDF: IS-3M, captured from Egypt in 1967.
 * 🇰🇵 North Korea
 * Korean People's Army: Small number of IS-2s; never deployed in combat in the Korean War.
 * 🇵🇱 Poland
 * Polish Land Forces: Approximately 71 IS-2s used in combat between 1944-1945. 180 IS-2s survived as of 1955, and remained in service until the 1960s; some later were converted to armoured recovery vehicles. Two IS-3s were bought in 1946 for trials only.
 * 🇷🇴 Romania
 * Romanian Land Forces: About 5 IS-3s.
 * South Ossetia
 * South Ossetian Army: Operated some IS-2s, IS-3s and T-10s until 1995.
 * USSR
 * Red Army: Heavy Breakthrough Tank from 1944-1945.
 * Soviet Army: Phased out of service in the early 1970s.

Surviving vehicles
There are several surviving IS series tanks, with examples found at the following:
 * IS-2
 * Os. Górali [standing tank], Kraków, Poland
 * Polish Army Museum, Warsaw, Poland
 * Museum of Arms in Fort Winiary, Poznań, Poland
 * Museum of Armoured Weapon in Training Center of Land Forces, Poznań, Poland (operational, see movie)
 * Tank Museum of the People's Liberation Army, Beijing, China.
 * Liberty Park, Overloon, The Netherlands.
 * Museum of the Great Patriotic War, Kiev, Ukraine
 * Kurzeme Fortress Museum, Zante, Latvia.
 * Diorama Battle of Kursk, in Belgorod, Russia.
 * IS-2M
 * Army Technical Museum, Lešany, Czech Republic (previously in Prague as a Monument to Soviet tank crews)
 * Imperial War Museum Duxford, England.
 * Kubinka Tank Museum, Russia.
 * Victory Park at Poklonnaya Gora, Moscow, Russia.
 * IS-3
 * IDF Armoured Corps Museum, Israel.
 * Museum of Armoured Arms, Training Center of Land Forces, Poznań, Poland (the only one still operational)
 * Army Technical Museum, Lešany, Czech Republic.
 * Polish Army Museum, Warsaw, Poland. (Fort Czerniaków branch of the Museum).
 * United States National Armor & Cavalry Museum, Fort Benning, Georgia, USA.
 * Victory Park in the northern part of Ulyanovsk, Russia.
 * Ulyanovskoe SVU, Ulyanovsk, Russia
 * Royal Museum of the Armed Forces and of Military History, Brussels, Belgium.
 * Military Glory Museum, Gomel, Belarus.
 * Diorama Battle of Kursk, in Belgorod, Russia.
 * IS-3M
 * Egyptian National Military Museum, Cairo Citadel, Egypt.
 * Military Vehicle Technology Foundation, California, USA.
 * IS-4
 * Kubinka Tank Museum, Russia.


 * IS-7
 * Kubinka Tank Museum, Russia.

Tanks of comparable role, performance and era

 * Tiger I : German Equivalent of IS-2
 * Tiger II : German Equivalent of IS-3
 * M26 Pershing : approximate US equivalent