IS-2
Joshbaumgartner · CC BY-SA 4.0
The IS-2 (ИС-2, also written as JS-2) was a Soviet heavy tank, the second model in the IS series named for Joseph Stalin. It was built for and fought in World War II, and later served in other Soviet-aligned nations.
The KV-1 heavy tank drew criticism from its crews for poor mobility and a gun no larger than the T-34 medium tank’s, while costing much more without offering better combat performance. Moscow ordered some KV-1 lines to switch to T-34 production, threatening the closure of the SKB-2 design bureau under Kotin. In 1942, the KV-1S partially addressed this by using thinner armor to become lighter and faster, matching the T-34’s mobility but losing its armor advantage. KV-1S production ended in April 1943, gradually replaced by the SU-152.
After capturing a German Tiger tank in January 1943, the decision was made to develop a new heavy tank, codenamed Object 237. Before it was ready, heavy fighting in summer 1943 required an immediate response. Dukhov’s team created the stopgap KV-85, mounting the 85 mm D-5T gun (from the SU-85) on a KV-1S hull. The KV-85 used an Object 237 turret, requiring a modified hull with a larger turret ring and fillets. The radio operator’s position became an ammunition rack, and the hull machine gun was fixed on the driver’s side for him to operate. Between September and October 1943, 130 KV-85s were built before lines shifted to the IS series. Like the KV-1S, the KV-85 was quickly outclassed by the IS tanks.
The Object 237 prototype, derived from the canceled KV-13, entered production as the IS-85 heavy tank. First deliveries came in October 1943, and production ended in January 1944. It was renamed IS-1 after the IS-122 appeared, which was later called IS-2 for security.
By 1943, the T-34 could mount an 85 mm gun, matching the KV-85’s firepower. Efforts to up-gun the IS-85 began in late 1943. Two candidates were the D-25 122 mm gun (ballistically identical to the A-19) and the D-10 100 mm gun (derived from a naval dual-purpose gun). The D-10 had better armor penetration but a less effective high-explosive round, and it was a new weapon in short supply, while the A-19 and its ammunition had excess production capacity. Compared to the older 76.2 mm F-34, the D-25 delivered 5.37 times the muzzle energy.
After testing both guns on the IS-122, the D-25 was chosen. It used separate shell and powder charges, giving a lower rate of fire than single-piece ammunition—a serious drawback in tank duels. Soviet tests showed the D-25 could penetrate a Panther’s front armor at 2,500 m, while the D-10 could do so at 1,500 m, so the D-25 was considered adequate. First IS-122s with this gun were delivered in December 1943.
A German Wa Pruef 1 report from 5 October 1944 estimated that the A-19 gun could not penetrate a Panther’s upper glacis at any range, could penetrate the lower glacis at 100 m, the mantlet at 500 m, and the front turret at 1,500 m. The Panther’s side armor could be penetrated at 3,500 m. Tests with captured Tiger I tanks at Kubinka showed the D-25T could penetrate the Tiger’s turret at 1,000–1,500 m and the front hull weld joints at 500–600 m. In 1944, the only armor-piercing round was the BR-471; an improved BR-471B was developed in spring 1945 but only became available in quantity after the war.
The same German report estimated that at 30 degrees obliquity, a Tiger I could defeat the IS-2 model 1943’s driver’s front plate and nose at 100–300 m, while the IS-2’s 122 mm gun could penetrate the Tiger’s front armor at 500–1,500 m. A Panther had to close to 600 m to guarantee penetration of the IS-2’s frontal armor (its 75 mm gun could penetrate the mantlet at 400 m, front turret at 800 m, and driver’s plate at 600 m), while the IS-2 could penetrate the Panther at 1,000 m. However, by summer 1944, a German shortage of manganese forced them to use high-carbon steel alloyed with nickel, making armor brittle, especially at welds. This improved the performance of the IS-2’s 122 mm AP shells against the Panther, and front-line reports described cases where...
- field
- Armored fighting vehicle
- nationality
- Soviet
- production_start
- December 1943
- crew
- Not specified in article
Quick Facts
- Origin
- Soviet Union
- Is Ranged
- Yes
- Service
- 1944–1970s
- Used By
- See Operators
- Wars
- World War II, Korean War
- Designer
- Zhozef Kotin / Nikolay Dukhov
- Number
- 3,854 (all models)
- Spec Label
- IS-2 Model 1944Zaloga · Grandsen · 1984 · p=176
- Length
- 9.90 m
- Height
- 2.73 m
- Design Date
- 1943
- Manufacturer
- Kirov Factory, UZTM
Facts from the source article.
Lore & Background
The IS-2, initially designated the IS-122, was developed following late 1943 efforts to improve the armament of the earlier IS-85. The selected main gun was the D-25, a 122 mm weapon ballistically identical to the A-19 field gun. This weapon used separate shells and powder charges, which slowed the rate of fire compared to tanks using single-piece ammunition. However, Soviet tests showed the D-25 could penetrate the front armor of a German Panther tank at 2,500 meters, while a competing 100 mm gun could only do so at 1,500 meters. The first IS-122s were delivered in December 1943. The tank was slightly lighter and faster than the heaviest KV model from 1942, while featuring thicker front armor and a much-improved turret design. Its hull design, a staple of the IS series, eliminated the hull machine-gunner and radio operator, with the driver operating a fixed hull machine gun. The IS-2’s 122 mm gun delivered over five times the muzzle energy of the older 76.2 mm F-34 gun. Against a captured Tiger I, the D-25 could penetrate the turret from 1,000 to 1,500 meters and the front hull weld joints at 500 to 600 meters. A German report estimated the IS-2’s frontal armor could be defeated by a Tiger I only at very close ranges of 100 to 300 meters, while the IS-2 could penetrate the Tiger’s front armor from 500 to 1,500 meters.
Reader's Guide
The IS-2's significance lies in its role as a Soviet heavy tank during World War II, providing a heavily armed and armored vehicle that could engage German heavy tanks. The tank's armor was primarily cast, reducing production costs but sometimes resulting in brittle armor due to lower-quality alloys. The IS-2 saw service in other Soviet allied countries after the war, extending its legacy beyond World War II. Its development reflected the Soviet response to German heavy tanks like the Tiger and Panther, and it remained in service for years after the conflict.
Did You Know?
- The D-25 gun delivered 5.37 times the muzzle energy of the older F-34 76.2 mm tank gun.
- The IS-2 carried only 28 rounds of ammunition, typically 20 high explosive and 8 armor-piercing.
From KV-1 to IS-2: A Lineage of Compromise
The IS-2 did not emerge fully formed; it was the endpoint of a long, troubled chain of Soviet heavy-tank development. The original KV-1 drew complaints from its own crews over sluggish mobility and a main gun that lagged behind the T-34's, and Moscow's decision to divert KV-1 assembly lines to T-34 output nearly ended the heavy-tank program altogether. The lighter, faster KV-1S offered a partial fix but sacrificed the thick armor that had defined the series, and it was phased out by April 1943.
Choosing the 122: Firepower and Its Trade-offs
By late 1943 the IS-85's 85 mm gun had lost its edge, especially after the same caliber was fitted to the T-34. The D-25 won partly on industrial pragmatism—the Soviet base had surplus A-19 production capacity while the D-10 was in short supply. The cost was a separate shell-and-charge loading cycle that depressed rate of fire, a real disadvantage in tank-versus-tank duels. The first IS-122s carrying this gun reached units in December 1943.
Steel Against Steel: The IS-2 in Tank Duels
Steven Zaloga observed that below 1,000 m the IS-2 and Tiger I could each destroy the other, with crew skill and tactical situation ultimately deciding the outcome.
Production Rhythm and Postwar Service
The IS-2's production history mirrors the urgency of Soviet wartime industry. As the second tank in the series bearing Joseph Stalin's name, the IS-2 carried both a political and a technical legacy. Beyond the Soviet Union, the tank continued to serve in allied countries well after the war.
Common Misconceptions (Editorial)
A common misconception is that the IS-2 used single-piece ammunition like many contemporary tanks, but its D-25 gun used separate shell and powder charges, which resulted in a lower rate of fire. Another misconception is that the IS-2 was the first in its series, but it was actually the second IS tank, following the IS-1 (IS-85); some IS-1s were even rearmed as IS-2s before leaving the factory.
Why It Matters (Editorial)
The IS-2 endures as a symbol of Soviet industrial and military resilience during World War II, representing the shift toward heavier firepower and armor that defined late-war armored engagements. Its development and deployment highlight the urgent wartime need to counter German heavy tanks, and its continued service in allied countries after the war underscores its lasting impact on Cold War-era armored doctrine.
Gallery
Frequently Asked Questions
What is the IS-2?
The IS-2 is a Soviet heavy tank that was the second vehicle in the IS series. It was built during World War II and is widely recognized for its large-caliber main gun and heavy armor.
What does the 'IS' in IS-2 stand for?
The designation honors Joseph Stalin, the Soviet leader who gave his name to the entire family of IS-series heavy tanks.
When did IS-2 production begin?
Factory output started in December 1943, just in time for the tank to see frontline action in the war's final years. After 1945, surplus units were transferred to several Soviet-allied nations for continued service.
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