Type Heavy tank Designer Zh. Kotin, N. Dukhov | Place of origin Soviet Union | |
 | ||
Used by Soviet Union, China, Cuba, Czechoslovakia, DPRK, Egypt, Poland Wars World War II
Hungarian Revolution of 1956
Six Day War
Warsaw Pact invasion of Czechoslovakia
War in Donbass Designed 1943 (IS-2)
1944 (IS-3)
1944–45 (IS-4) | ||
The IS Tank (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. The heavy tank was designed with thick armor to counter German 88 mm guns and carried a main gun capable of defeating 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 went into service in April 1944 and was used as a spearhead by the Red Army in the final stage of the Battle of Berlin.
Contents
KV-85 and IS-85/IS-1
The KV-1 was criticized by its crews for its poor mobility and the lack of a gun heavier than the T-34 medium tank. It was much more expensive than the T-34, without having greater combat performance. Moscow ordered some KV-1 assembly lines to shift to T-34 production, leading to fears that KV-1 production would be halted and the SKB-2 design bureau, led by Kotin, closed. In 1942, this problem was partially addressed by the KV-1S tank, which had thinner armor than the original, making it lighter and faster. It was competitive with the T-34 but at the cost of no longer having the heavier armor. Production of the KV-1S was gradually replaced by the SU-152 and ended in April 1943.
The capture of a German Tiger tank in January 1943 led to a decision to develop a new heavy tank, which was given the codename Object 237. Before Object 237 had time to mature, intense tank fighting in the summer of 1943 demanded a response. Dukhov's team was instructed to create a stopgap KV tank, the KV-85, which was armed with the 52-K-derivative gun of the SU-85, the 85 mm D-5T, that proved capable of penetrating the Tiger I from 500 m (550 yd). The KV-85 was created by mounting an Object 237 turret on a KV-1S hull. To accommodate the Object 237 turret, the KV-1S hull was modified, increasing the diameter of the turret ring with fillets on the sides of the hull. The radio operator was replaced with an ammunition rack for the larger 85 mm ammunition. The hull MG was then moved to the opposite side of the driver and fixed in place to be operated by the driver. There was a short production run of 148 KV-85 tanks that were sent to the front beginning in September 1943. Production ended by December.
The Object 237 prototype, a version of the cancelled KV-13, was accepted for production as the IS-85 heavy tank. First deliveries were made in October 1943, and the tanks went immediately into service. Production ended in January 1944. Its designation was simplified to IS-1 after the introduction of the IS-122, later renamed as IS-2 for security purposes.
Gun
By 1943 engineers had succeeded in mounting the 85 mm gun to the T-34-85, making the IS-85 superfluous. Efforts to up-gun the IS-85 began in late 1943. Two candidate weapons were the D-25 122 mm tank gun, ballistic characteristics of which were identical to the A-19 122 mm gun, and the D-10 100 mm gun, based on a naval dual-purpose gun. The D-10 had been designed for anti-tank fire and had better armor penetration than the A-19, 185 mm compared to 160 mm but the smaller calibre meant it had a less useful high explosive round. Also, the D-10 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 F-34 76.2 mm tank gun, the D-25 delivered 5.37 times the muzzle energy, while it had similar accuracy to that of the 88 mm L/71 gun mounted on the Tiger Ausf B.
After testing both guns on the IS-122 and IS-100 respectively, the former was selected as the main armament of the new tank, because of its availability and the effect of its large high-explosive shell against German fortifications. The D-25 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. Soviet proving-ground tests claimed that the D-25 could penetrate the front armor of the German Panther tank at 2,500 metres (2,700 yd) while the D-10 could do so at a maximum range of 1,500 metres (1,600 yd). It was therefore considered an adequate anti-tank gun.
A Wa Pruef 1 Report dated 5 October 1944 has data on the penetration ranges of the 122 mm A-19 gun against a Panther tank angled at 30 degrees; this estimated that the A-19 gun was unable to penetrate the glacis plate of the Panther from any distance, could penetrate the lower glacis plate of the hull from 100 metres (110 yd), could penetrate the mantlet from 500 metres (550 yd) and could penetrate the front turret from 1,500 metres (1,600 yd). The Panther's 40–50 millimetres (1.6–2.0 in) thick side armor would have been exposed and vulnerable at such angle; the sides at 30 degrees are penetrable from over 3,500 metres (3,800 yd) according to the same Wa Pruef 1 report. Testing with captured Tiger Ausf Bs in Kubinka claimed that the 122 mm D-25T was capable of penetrating the Tiger Ausf B's turret from 1,000–1,500 metres (1,100–1,600 yd) and the weld joint or edges of the front hull plates at ranges of 500–600 metres (550–660 yd). In 1944 the BR-471 was the sole armour-piercing round available. An improved version, the BR-471B (БР-471Б) was developed in early 1945, but was available in quantity only after World War II ended.
The large 122 mm HE shell was its main asset, proving highly useful and destructive as an infantry-killer. In extremis the IS-2 engaged enemy heavy armour with OF-471 (ОФ-471) high explosive projectiles. These shells had a mass of 25 kg, a muzzle velocity of 800 m/s, and were equipped with a 3.8 kg TNT charge. Mechanical shock and explosion was often enough to knock out enemy heavy tanks without any armour penetration.
The most recognizable disadvantage of the D-25T gun was its slow rate of fire due the massive size and weight of the shells; only one to one and a half rounds per minute could be fired, initially. After some modernizations and the additional semi-automatic drop breech over the previously manual screw breech, the rate of fire increased to 2–3 rounds per minute. According to Steven Zaloga, the increase amounted to 3–4 rounds per minute. Another limitation imposed by the size of its ammunition in a relatively small vehicle was the ammunition stowage; only 28 rounds could be carried inside the tank, with a complement of 20 HE rounds and 8 AP rounds the norm.
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. It was slightly lighter and faster than the heaviest KV model 1942 tank, with thicker front armor and a much-improved turret design. The tank could carry thicker armor than the KV series, while remaining lighter, due to the better layout of the armor envelope. The KV's armor was less well-shaped and featured heavy armor even on the rear, while the IS series concentrated its armor at the front. The IS-2 was slightly lighter than the Panther, much lighter than the Tiger I and Tiger II and had a lower silhouette than both. Western observers tended to criticize Soviet tanks for their lack of finish and crude construction. The Soviets argued 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 anti-aircraft machine guns and had narrow mantlets. According to Steven Zaloga, the IS-2 and Tiger I could knock each other out in normal combat distances below 1,000 m (1,100 yd). At any range, the performance of each tank against each other was dependent on the crew and combat situation.
In late 1944, the stepped hull front was replaced with an improved single casting of 120 mm thickness angled at 60 degrees. This new nose lacked the opening driver's visor. It is sometimes incorrectly referred to as the IS-2m, but that designation actually refers to a much later modernization program from the 1950s. Other minor upgrades included the addition of a travel lock on the hull rear, wider mantlet and, on very late models, an anti-aircraft machine gun.
In the mid-1950s, the remaining IS-2 tanks (mostly model 1944 variants) were upgraded to the IS-2M standard, 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 two tanks known as IS-3: Object 244 was an IS-2 rearmed with the long-barrelled 85mm cannon (D-5T-85-BM) and developed by LKZ (in Leningrad), which was never series-produced for service use.
Object 703 was developed in late 1944 by ChTZ (in Chelyabinsk) and left the factory shop in May 1945. This tank had an improved armour layout, and a semi-hemispherical cast turret (resembling an upturned soup bowl) which became the hallmark of post-war Soviet tanks. While this low, hemispherical turret improved protection, it also significantly diminished the headroom, especially for the loader. The low turret also limited the maximum depression of the main gun, since the gun breech had little room inside the turret to elevate, and this limited the extent to which the IS-3 could take advantage of hull-down positions compared to higher Western tanks. The IS-3's pointed prow earned it the nickname Shchuka (Pike) by its crews. It weighed slightly less and stood 30 centimetres (12 in) 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 first public demonstration of the IS-3 came on 7 September 1945 during the Allied victory parade on Charlottenburger Straße in Berlin, with the heavily reinforced 71st Guards Heavy Tank Regiment of the 2nd Guards Tank Army. 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 two tanks known as IS-4: Objekt 245 and Objekt 703. Objekt 245 was an IS-2 rearmed with a long 100mm D-10T cannon. The other IS-4 was a new vehicle projected by LKZ in parallel with the IS-3 known as Objekt 703 by the same design and development bureau. For the latter, the IS-2 hull was lengthened, with an extra set of road wheels added and an improved engine. Both hull and turret armor were increased. Several alternative armaments were explored in paper studies but ultimately the IS-2's original 122 mm 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 Objekt 703'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
There existed two different IS-6s: the Object 253 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, and development was discontinued. The alternative Objekt 252 shared the same hull and turret as the Object 253, but used a different suspension with no return rollers, and a conventional mechanical transmission. The design was deemed to offer no significant advantages over the IS-2, and the IS-6 project was halted.
IS-7
The IS-7 heavy tank was developed in 1948. Weighing 68 tonnes, thickly armoured and armed with a 130mm S-70 long-barrelled gun, it was the largest and heaviest member of the IS family. The armour was engineered in a similar fashion to the IS-3, with a pike nose on the upper glacis. When shot at frontally, the extreme angle that the pike nose presents results in a much higher likelihood of a ricochet. Thus, the armour protection could be enhanced without having to use excessive amounts of materials. However, if the pike nose was shot at a sideways angle, it would not have a relative thickness high enough to ricochet the shell. In spite of its weight, it was easy to drive due to numerous hydraulic assists. The loaders noted that the IS-7 was comfortable and that the autoloader was easy to use. It was also able to achieve a top speed of 60 km/h thanks to a 1050-horsepower engine giving it a power to weight ratio of 15.4 hp/tonne, a ratio superior to most contemporary medium tanks. Its armour was not only immune to the Jagdtiger's 12.8 cm Pak 44 but was even proof to its own 130mm. Due to the reasons unknown, most likely because of the considerable issues arising from its mass (bridges, rail transport - no Soviet/Russian tank accepted into service afterwards exceeded 55 t), the tank never reached the production lines.
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.
The T-10M is the final iteration of this type. It featured a longer gun barrel than previous models with 5-baffle muzzle brake and 14.5mm machine gun. 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 the elite Guards 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.
According to German tactical instructions, a Panther had to close to 600 m (660 yd) to guarantee penetration of the IS-2's frontal armor, while the IS-2 could penetrate the Panther at ranges of 1,000 m (1,100 yd). The hull armor of the Soviet IS-2 model 1943 would be defeated by Tiger I between 100 and 300 m (0.062 and 0.186 mi) at the driver's front plate and nose., while the IS-2's 122 mm gun could penetrate the Tiger's front armor from between 500 and 1,500 m (0.31 and 0.93 mi).
The IS-2 tank first action was in February 1944 at Korsun-Shevchenkivskyi, Ukraine. A single unit of 10 IS-2s from the 72nd Regiment engaged and claimed to have destroyed no less than 41 German tank and SPGs (including many of Tiger I), three AFVs and 10 anti-tank gun in several engagements between April and May 1944, claiming the loss of eight IS-2 tanks.
The 78th Tank Regiment, in the Battle of Debrecen (October 1944), destroyed 6 Tigers, 30 Panthers, 10 Panzer IV tanks, 1 Ferdinand, 24 self-propelled guns, 109 guns, 38 armored personnel carriers, 60 machine-gun points, 2 warehouses with ammunition and 12 aircraft at the airport. The losses of the regiment during this period: two IS-2 was destroyed, and 16 more was damaged.
In the Vistula-Oder offensive, The 72nd Tank Regiment was also successful. From January 14 to January 31, 1945, they destroyed 19 enemy tanks, 41 guns, 15 machine-gun points, 10 mortars and 12 dugouts, without any Soviet losses.
During the defense of the Narevsky bridgehead (January 15, 1945), the crew of the one IS-2 tank (30th Guards heavy tank brigade) under the command of Lieutenant Ivan Ivanovich Khitsenko (Иван Иванович Хиценко) entered the battle with 10 Tiger I tanks. They destroyed 5 enemy tanks, before themself had been killed by enemy fire
The IS-2 proved to have surprisingly good anti-tank capabilities due to the D-25T's extremely heavy HE projectiles. Standard doctrine for purpose-built anti-tank guns of the period universally relied on small, dense solid projectiles propelled to high velocities, optimized for punching through armor. However, the 122mm HE shell would easily blow off the driver sprocket and tread of the heaviest German tank. Between 12 and 13 August 1944 (when the Tiger II was first used on the Eastern Front), up to six Tiger II were lost in Baranów Sandomierski to fire of Soviet IS-2 tanks, which opened fire HE shell at ranges from 700 to 1.000 meters, without any Soviet losses.
Performed on captured Tiger Ausf-B tanks in Kubinka in 1944 showed that the IS-2 was able to destroy them at any range with a fair degree of reliability. Tiger Ausf-B front armor plate cannot be penetrated by 122mm AP shell, but heavily damaged by 122mm armor piercing/high explosive shells, the result is the damage of the tank's mechanical components. Even when 122mm shells did not penetrate the armour, there was often a large amount of spalling from the inside of the plates, which killed the crewmen, damaged the transmission and rendered the tank inoperable.
By the 1950s, the emergence of the main battle tank concept—combining medium-tank mobility with the firepower and armor of the heavy tank—had rendered heavy tanks obsolete. 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 modernized as IS-3M models. The Egyptian Army acquired about 100 IS-3M tanks 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 armor, 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 armor of the IS-3s at normal battle ranges. There were a number of engagements between the M48A2 Pattons of the IDF 7th Armored 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 90 mm 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 favor of the Type 59, a copy of the Soviet T-54A.
Models
Operators
Surviving vehicles
There are several surviving IS series tanks, with examples found at the following: