IS-2 Heavy Tank

 IS-2 Heavy Tank

IS-2 tanks in Vyborg 1944

 

Striving to create a new heavy tank that would retain the best features of the KV tanks, but would be lighter in weight and easier to manufacture, the Special Design Bureau No. 2 (SKB-2) at the Chelyabinsk Kirov Plant started intensive design and construction work from March 1942 . The result was over a dozen designs for tanks and other vehicles, the most important being the KV-1s, KV-8, KW-85 and KW-13.

Experimental tank IS-85 later re-designated as IS-1 Plant 100 Chelyabinsk, July 1943

 

 In the fall of 1942, the head of SKB-2 Ż. Kotin started designing a new heavy tank. From the KV-13 tank, a fairly carefully profiled hull made of cast elements, a new efficient and rarely failing drivetrain, an effective engine cooling system and a modernized chassis were taken over. The tank was named Josif Stalin (abbreviated as IS) and from the beginning it was designed in two versions with different armament. A vehicle armed with a 76.2 mm cannon received the factory designation "IS-1 model 1 tank, Object 2331S", and with a 122 mm howitzer - "IS-2 model 2 tank, Object 2341S".

IS-2 in Poznan February 1945

 

At the same time, in April 1943, further prototypes of IS tanks were prepared, but armed with 85 mm guns. Shortly after the tests at the training ground in Gorokhovets on August 7, 1943, the State Defense Committee adopted a heavy IS tank armed with an 85 mm D-5T cannon. It received the designation IS-1. From October 1943 to January 1944, 107 tanks of this type were produced. Test firing of 85 mm cannons at a captured PzKpfw tank. VI "Tiger" and the conclusions of the Battle of Kursk showed the limited effectiveness of guns of this caliber. Therefore, on September 4, 1943, the State Defense Committee ordered the installation of more powerful cannons in IS heavy tanks, but there was no suitable gun at that time. After a series of theoretical calculations, Z. Kotin and F. Petrov came to the conclusion that the IS tank should be armed with a 122 mm gun. 

IS-2 and Germany 1945

 

Before such a gun existed in the form of a prototype, on October 31, 1943, Stalin and the State Defense Committee decided to adopt the IS tank with a 122 mm cannon. F. Petrov's team built the first experimental copy of the 122 mm D-25T gun only two weeks later (November 12, 1943). The prototype of the tank with the new cannon, called IS-122 (Object 240), was completed at the end of November 1943. The results of the test firings were satisfactory, although it should be noted right away that the gun was not a miracle of technology. In terms of armor penetration, it was comparable to the German 88 mm Pak 43 gun, with much better ballistics and firing more modern ammunition. From December 1943 to December 1945, 4,392 IS-2 heavy tanks were produced (in April 1944, IS tanks with a 122 mm gun were designated as such).

Destroyed IS-2 of the 6th Independent Guards Heavy Tank Regiment, Romania May 1944

The hull of the IS-1 tank was welded from cast and rolled armor plates. The armor thickness of the front part of the hull was: bottom plate 100 mm, top plate 60 mm, turret base 120 mm, sides 90 mm, rear 60 mm, top plate and bottom 20-30 mm. In the front part of the hull, on the right side, there was a stationary 7.62 mm DT machine gun, operated by a loader, in the longitudinal axis of the tank. The combat weight of the tank was 44 tons

The tower was cast. It had a streamlined shape and all edges were rounded. The thickness of the turret armor was variable. In the front part it was 100 mm, sides 90 mm, rear 60 mm, ceiling 30 mm.

In the front part of the hull, in the driver's compartment, in the center was the driver-mechanic. It observed the terrain through a large observation slit in the small forward hatch and two observation periscopes. To its left and right were the two main fuel tanks. Access to the control compartment was possible only through hatches in the turret.

A column of IS2 tanks 1945

The IS-1 tank was powered by a 12-cylinder water-cooled W-2-IS (W-2-10) 520 hp (382.2 kW) diesel engine at 2,000 rpm. The total capacity of the fuel tanks was 520 dm³. Four additional tanks, carried on special handles on the sides of the rear part of the hull, contained 300 dm³ of fuel.
The landing gear consisted of 10 double steel road wheels, a pair of idler wheels at the front and a pair of drive wheels at the rear. The road wheels were independently suspended on torsion bars. The upper part of the track was supported by three double rollers. The track width was 650 mm. The IS-2 tank retains all the basic structural elements and equipment of the IS-1 tank, with the exception of the turret with armament and the chassis (12 road wheels). Of course, some changes were made in the course of production, modernizing the hull structure and replacing some instruments with newer ones. The IS-2 tank had a slightly modernized turret in comparison to the IS-1, in which the 122 mm D-25T gun was placed. Some of the tanks were mounted on a special base, mounted on the commander's turret, wkm DSZK wz. 1938 cal. 12.7mm. It was to be used mainly for combating air targets. The ammunition supply for the gun was only 28 rounds, for the DT-2331 machine gun, and for the DSZK-250 machine gun. The gunner had a 10T-17 telescopic sight and a PT4-17 periscope sight. The latter was replaced in the spring of 1944 by the MKIV rotary periscope. In turn, the commander received the TPK-1 observation device. Subsequently, the 10T-17 sight was replaced sight TSZ-17. 

The IS-2 tank turned out to be exceptionally long-lived. In the years 1944-1947, projects of a dozen or so heavy tanks were created in the USSR, which were to replace the IS-2. However, these tanks were too complicated, expensive to produce and expensive to operate, so the war veteran was never replaced. The IS-2 tank was constantly modernized. The IS-2M tank, with significantly improved combat and technical characteristics, remained in service with the Soviet Army until the 1980s. It was officially withdrawn from service by order of the Minister of Defense of the Russian Federation only in 1995.

On the chassis of the IS heavy tank, huge numbers were produced (in the period 1944 - September 1945, a total of as many as 4,635 copies, and until the end of production in 1947 - 6,102 copies.