Iosif Stalin IS-2

By 1943 the Soviet KV series of heavy tanks had run out of road. The KV-1 had been a brutal shock to the Germans in 1941, but it was slow, mechanically troublesome and, crucially, armed with the same 76 mm gun as the far cheaper T-34 — it offered little extra firepower for all its bulk. The appearance of the German Tiger made the need for a genuinely more powerful Soviet heavy tank urgent.

The answer was a new family of heavies named for Iosif Stalin. The first, the IS-1, mounted an 85 mm gun, but Soviet designers quickly went much further. Reasoning that a heavy tank's real job was to break through fortified lines and destroy enemy heavy tanks and strongpoints, they fitted the largest gun the turret could take — a tank version of the formidable 122 mm field gun — and so created the IS-2.

The IS-2's defining feature was its enormous 122 mm D-25T gun. Its armour-piercing shell was so heavy and fast that it could defeat the frontal armour of a Tiger or Panther, and its huge high-explosive round was devastating against bunkers, buildings, guns and infantry — exactly the targets a breakthrough tank was meant to destroy. No other tank of the war carried so large a gun in a fully rotating turret.

Just as impressive was how much protection the Soviets packed into so compact a vehicle. At around 46 tonnes — far lighter than a Tiger, let alone a King Tiger — the IS-2 carried very thick, well-sloped armour, and later production reworked the hull front into a clean sloped 'stepped' nose that made it extremely hard to penetrate. It was a masterclass in efficient design: heavy-tank firepower and protection on a chassis that remained reasonably mobile and, by Soviet standards, buildable in quantity.

The great compromise lay in the gun's ammunition. The 122 mm rounds were large and heavy, loaded in two separate pieces, which made for a slow rate of fire and meant only around 28 rounds could be carried. In a fast-moving tank-versus-tank duel this was a real weakness — but for its intended role of methodical, hard-hitting breakthrough work, it was a price worth paying.

The IS-2 was refined steadily in production, the most important change being the move from the early stepped 'broken nose' hull to the cleaner cast sloped glacis of the IS-2 model 1944, which improved both protection and manufacturability. Improvements to the gun mount, optics and engine deck followed as the design matured.

The IS chassis also became the basis for a powerful family of vehicles. It led to the even more heavily armoured IS-3, which arrived right at the war's end and stunned Western observers with its rounded 'pike' nose, and to a series of massive assault guns and tank destroyers — the ISU-122 and ISU-152 — that mounted heavy guns in a fixed casemate and earned the nickname Zveroboy, the 'beast-killer', for their effect on German armour.

The IS-2 reached the front in early 1944 and was organised into elite independent heavy tank regiments, often given Guards status, that were attached to spearhead the great Soviet offensives. Its job was to lead the assault on the most heavily defended sectors — smashing fortifications, demolishing strongpoints and dealing with German heavy tanks so that the lighter T-34s could pour through the gap.

The weapon that made this possible was its enormous 122 mm D-25T gun. Its shell was so heavy it had to be loaded in two pieces, slowing the rate of fire to a handful of rounds a minute — but a single hit could tear the turret off a Tiger or bring down a building whole. The IS-2 was not a duellist; it was a battering ram, and the Red Army built it to break in.

In that role it excelled. From the breakthroughs of 1944 across Belorussia and into Poland, through the bitter fighting in the cities of central Europe, the IS-2’s gun proved ideal for the close, brutal work of urban and fortified combat. In the battle for Berlin in 1945, IS-2 regiments blasted their way through the German capital street by street, their 122 mm shells collapsing the buildings from which the defenders fought.

Against German heavy tanks the picture was more mixed — the slow-firing gun put a premium on the first shot — but the IS-2 could and did destroy Tigers and Panthers, and it utterly outmatched the lighter German tanks it usually met. Tough, hard-hitting and available in real numbers — some 3,800 built by war’s end — it became the armoured fist of the Red Army’s final drive into the Reich.

The IS-2 was the finest heavy tank the Soviet Union fielded in the war and, in many respects, a more rational design than its German rivals. Where the Tiger II chased invulnerability at the cost of mobility and numbers, the IS-2 struck a far better balance — enough armour, a shattering gun, and a weight and cost that allowed nearly 3,850 to be built and sent to the front in time to matter.

It was not a tank for winning long-range duels; its slow, two-piece ammunition saw to that. But as a breakthrough weapon — the role it was actually designed for — it was superb, and it played a leading part in the Red Army's advance from the 1944 offensives all the way to the streets of Berlin. The IS-2 stands as the Soviet answer to the German heavies: less fearsome in a single duel, but far more effective in the war that was actually fought.

• Steven J. Zaloga & Jim Kinnear, IS-2 Heavy Tank 1944–73 (Osprey, New Vanguard).
• Maxim Kolomiets, IS: The Complete History of the Stalin Heavy Tanks.
• Mikhail Baryatinskiy, IS-2 Heavy Tank (Ian Allan).