IS tank family


The IS Tank was a series of heavy tanks developed as a successor to the KV-series by the Soviet Union during World War II. The IS acronym is the anglicized initialism of Joseph Stalin. The heavy tanks were designed with thick armor to counter German 88 mm guns and carried a main gun capable of defeating Panzer IV tanks. They were mainly designed as breakthrough tanks, 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. The IS-3 served on the Chinese-Soviet border, the Soviet invasion of Hungary, the Prague Spring and on both sides of the Six-Day War. The series eventually culminated in the T-10 heavy tank.

Design and production

Object 237 KV-85 IS-85/IS-1 and IS-2

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.

Object 703 IS-3

There are two tanks known as IS-3: Object 244 was an IS-2 rearmed with the long-barrelled 85 mm cannon and developed by the Leningrad Kirov Plant, which was never series-produced for service use.
The IS-3 known as Object 703 is a Soviet heavy tank developed in late 1944. Its semi-hemispherical cast turret, became the hallmark of post-war Soviet tanks. Its pike nose design was also mirrored by other tanks of the IS tank family such as the IS-7 and T-10 tank. Too late to see combat in World War II, the IS-3 participated in the Berlin Victory Parade of 1945, on the Chinese-Soviet border, the Soviet invasion of Hungary, the Prague Spring and the Six-Day War.

Object 701 IS-4

There are two tanks known as IS-4: Object 245 and Object 701. Object 245 was an IS-2 rearmed with a long 100 mm D-10T cannon.
The IS-4 known as the Object 701 was a Soviet heavy tank that started development in 1943 and began production in 1946. Derived from the IS-2 and part of the IS tank family the IS-4 featured a longer hull and increased armor. With the IS-3 already in production, and when sluggish mobility and decreased need for tanks became an issue, many were sent to the Russian Far East with some eventually becoming pillboxes along the Chinese border in the 1960s. Less than 250 were produced.

Object 705A IS-5

The IS-5, is merely one of the many designations given to what would ultimately become the T-10 tank.

Object 252/253 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 limited 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 Object 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, just the reload time was less, and the IS-6 project was halted.

Object 260 IS-7

The IS-7 heavy tank design began in Leningrad in 1945 by Nikolai Fedorovich Shashmurin and was developed in 1948. Weighing 68 tonnes, thickly armoured and armed with a 130 mm S-70 long-barrelled gun, it was the largest and heaviest member of the IS family.

Object 730 T-10

The IS-10 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 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 14.5 mm 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.

Comparisons

T-35T-100SMKKV-1
M1940		KV-1
M1941		KV-1
M1942		KV-1S
M1942		KV-85
M1943		IS-2
M1945 		IS-3
M1945
Crew11775555444
Weight 45585543454742.5464646.5
Main armament76.2 mm
M. 27/32		76.2 mm
L-11		76.2 mm
L-11		76.2 mm
F-32		76.2 mm
F-34		76.2 mm
ZiS-5		76.2 mm
ZiS-5		85 mm
D-5T		122 mm
D-25T		122 mm
D-25T
Ammunition100––111111114114702828
Secondary armament2×45 mm
5×7.62 mm		45 mm45 mm2×DT4×DT4×DT4×DT3×DT3×DT, DShK2×DT, DShK
Engine500 hp
M-17M gasoline		500 hp850 hp
AM-34		600 hp
V-2K diesel		600 hp
V-2		600 hp
V-2		600 hp
V-2		600 hp
V-2		600 hp
V-2		600 hp
V-2-IS
Fuel 910––600600600975975820520 + 270
Road speed 30353635352845403737
Road range 150–150335300250250250240150
Armor 11–3020–7020–6025–7530–9020–13030–8230–16030–16020–220

Combat history

The IS-2 saw combat late in World War II in small numbers, notably against Tiger I, Tiger II tanks and Elefant tank destroyers. The IS-3 saw service on the Chinese-Soviet border, the Soviet invasion of Hungary, the Prague Spring and on both sides of the Six-Day War. However the mobility and firepower of medium-tanks and the evolution of the main battle tank rendered heavy tanks obsolete.

Variants

;KV-85: A stopgap model built from a modified KV-1S hull mated to an Object 237's turret and armed with the 85 mm D-5T.
;IS-85 : 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-armor capabilities, the latter was chosen due to better all-around performance.
;IS-122 : 1943 model, armed with A-19 122 mm gun.
;IS-2 model 1944 :1944 improvement with D25-T 122 mm gun, with faster-loading drop breech and new fire control, and improved frontal hull armour using thinner armour with a more efficient shape.
;IS-2M: 1950s modernization of IS-2 tanks.
;IS-3:1944 armor 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: Modernized version of IS-3. Fitted with additional jettisonable external fuel tanks and improved hull welding.
;IS-4: 1944 design, in competition against the IS-3. Longer hull and thicker armor 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. The assisted loader can achieve up to 8 rounds per minute. Other equipment included stabilizers, infrared night scopes, and 8 machine guns. The hull armor was 150 mm placed at 50-52 degree angles. On the turret, the frontal thickness was 240–350 mm at an angle of 45-0 degrees. The IS-7 had a crew of five, with the driver in the hull, the commander and gunner in the front of the turret, with both loaders in the rear of the turret. A Slostin machine 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 armor. Renamed T-10 as part of the Destalinization of the Soviet Union in the 1950s.

Operators

; Novorossiyan rebels
There are several surviving IS series tanks, with examples found at the following:
; IS-2
; IS-2M
; IS-3
; IS-3M
; IS-4
; IS-7

Tanks of comparable role, performance and era