Monday 31 May 2021

IS-2 Front Line Impressions

The appearance of the heavy IS-2 tank was an unpleasant surprise for the Wehrmacht. The Germans could no longer rely on the qualitative supremacy that Tigers and Panthers enjoyed in 1943. The first battles with Soviet vehicles showed that the time of "big cats" was at an end.

For example, when the Germans tried to break through to the encircled Festung at Tarnopol, it was the 11th Guards Heavy Tank Regiment armed with IS tanks that played a key role in deflecting the German counterattack. Soviet tanks could fire at a range of 1200-1500 meters from their skillfully chosen positions, and expert snipers could hit even further.

"The resilience of the IS-2's armour allows it to combat enemy heavy tanks openly at a range of 1000 meters. Losses were only taken when fighting heavy tanks in ambush at a range of 300-400 meters. There were no losses from Faustpatrone, but minor damage was experienced (to road wheels, suspension arms, tracks, etc).

IS-2 tanks painted in winter camouflage loaded on a train.

The IS tanks had a good debut at other parts of the front as well. These successes left Soviet commanders with an overinflated opinion of the tank's capabilities. In a way the official name of IS tank regiments, "Heavy Guards Breakthrough Tank Regiment", contributed to this reputation. Meanwhile, the Germans worked out how to fight these tanks before too long.
"Since the IS-122 has a long point-blank shot range, high muzzle velocity, but low mobility, low rate of fire, and low ammunition capacity, it is impossible to use them for breakthroughs in forested and swampy terrain. Enemy tanks located in ambushes allow them to close in and shoot them at close range before our crews can discover them. In practice there were also other examples. The enemy places tanks in hull down positions, buries them in the ground and hides them. When an IS-122 crests the hill its gun and muzzle brake are seen first. The enemy aims at the muzzle brake and when the tank shows its turret they fire, hitting the gun mantlet and disabling the gun.

It is necessary to use IS-122 tanks in support of medium tanks. This way the full power of the D-25 gun is used and the crews are able to discover enemy tank ambushes when they fire at our medium tanks. The IS-122 can destroy them with precise fire from short stops.

It is senseless to use these tanks as a battering ram against even hurriedly prepared defenses in swampy and forested terrain without an escort of light and medium tanks. In pursuit, tank forces should be arranged in echelons and not stretched out in a line."

The desire of some commanders to "be strong everywhere"  also played a negative role. Having received their long-awaited tanks, they plucked the regiments apart to support as many of their units as possible.

"It is sensible to use the regiment as one unit without subordinating it to tank brigades or even tank battalions. Keep it for covering flanks and fighting enemy tanks. Rapid reassignment between brigades does not allow the staffs to learn to work together and build cohesion on the battlefield."

The reader must understand that anything can happen in war, especially a diverse spectrum of how commanders treat units that were assigned to them as reinforcement. Today they are here, tomorrow they will go somewhere else, and the objective will have to be carried out without any help. However, losses of temporarily assigned units were usually not met with as many repercussions.

 "It is necessary to use field artillery to attack targets designated by the tanks. For instance, on November 3rd, 1944, the commander of the 19th Tank Brigade was told where the enemy's anti-tank guns and tanks were located and asked to help our tanks move up with his assigned artillery. The commander refused to do this with the excuse that the roads are bad and that he has no shells."

IS-2 tanks and infantry on a narrow forest road. Karelia, vicinity of Vyborg, summer of 1944.

Another weakness of the IS-2 tank was the greater need for reconnaissance.
"It is impossible to use the tanks without reconnaissance, as the IS-122 is not very mobile and doesn't have enough time to locate enemy targets. It is necessary to have a reconnaissance section in the regiment within the HQ platoon subordinate directly to the chief of reconnaissance.

As a rule, infantry is not very well aware of the enemy in front of advancing units. Combined arms reconnaissance is few in number and cannot give information required for battle.

In tank units (heavy tank regiments and heavy SPG regiments) there is no reconnaissance at all, which leads to senseless personnel and materiel losses."

As you can see, the fact that cooperation between tanks and infantry existed does not mean that the tanks had the support and information they needed. It's not surprising that tank unit commanders turned into pack rats, insisting on keeping their own reconnaissance, their own motorized infantry, artillery that could match tank units in mobility, SPAAGs, and even organic fighter aircraft units! 

Heavy tanks were vulnerable at close range, which the Finns took advantage of. This IS-2 tank burned up in June of 1944 in the Tammisuo swamps near Vyborg when it was hit with a 75 mm Pak 40 gun.

Frequent reassignments and attempts to use the IS tanks as a panacea for any problem resulted in rapid wear of materiel. Not all commanders realized that off-road mobility and maneuverability may have been comparable to that of the T-34, but the reliability and cruising range were not. Growing pains were also discovered during intense usage of the new and often unrefined tanks.
"The maneuverability and off-road mobility of the ISU-122 and IS-122 is good for this type of vehicle. Combat experience shows that terrain suitable for the T-34 is also suitable for the ISU-122 and IS-122. Heavy SPGs and tanks are capable of traversing slopes and tilts prescribed by the tactical-technical specifications. On the march the IS-122 tanks are no worse than T-34 tanks.

The main defects include:

  1. The bolts holding the drive sprocket often weaken, oil leaks out, and the final drive bearings are destroyed.
  2.  Poor thermal hardening of the stamped tracks, sprocket crown, and drive sprocket. After 900-1000 km of driving the engine and other components are still suitable for service, but the tracks and sprocket need replacement.
  3. The servo mechanism is located under the engine and it's impossible to get to it to wash it and oil it. During usage the mechanism gets covered in dirt and the needle bearings of the servo arm jam. The main clutch then cannot be engaged and the tanks stop.
  4. The main clutch is not installed well. The driving drum band and fan turbine bolts weaken and are severed. 
  5. The instruments (manometer, aerothermometer, tachometer, etc) are attached on rigid mounts. When a shell strikes the armour the armour is not damaged, but the instruments are disabled.
  6. The gearbox is poorly centered. The gearbox casing causes cracks in the drive shaft bearings with vibration, the semi-rigid linkage bolts are torn.
Proposed improvements to improve assembly:

  1. Improve the drive sprocket mounting.
  2. Improve the thermal treatment of the stamped tracks. Better yet, use cast tracks, as those showed themselves well.
  3. Cover the servo mechanism with a casing and add an easily accessible oil conduit.
  4. Improve the gearbox centering and add more bolts to the semi-rigid linkage." 
A repair crew works on the "heart" of the IS-2 tank, the V-2IS engine.

Many of the complaints had to do with the crew's conditions. This was to be expected a no matter what the designers tried, the cost for a tank with thick sloped armour and a 122 mm gun was the placement of the crew. As with the ISU-152, the driver was the odd man out. His station was uncomfortable, hard to see from, and his job was physically demanding. Worst of all, he had a small chance of survival if he had to escape from a burning tank.
"The driver's job in heavy tanks and SPGs is uncomfortable due to the cramped driver's compartment and poor visibility through the vision port. If the IS-122 tank is hit and catches fire, the entire crew does not have time to exit through the sole hatch. The driver usually dies.

The periscopes are placed too high and not on the same level as the vision port. On the latest tanks the vision port has a large dead zone on off-road terrain, which makes driving difficult. 

On the IS-122:

  1. Having just one hatch makes exiting the tank difficult.
  2. It is difficult to access components for adjustment, especially the servo mechanism.
  3. It is difficult to rotate the turret by hand.
  4. The separate propellant round is hard to load." 

None of these issues overrode the fact that the IS-2 tank was one of the best if not the best among contemporary heavy tanks from the moment of its creation until the end of the war. It was very effective when used properly. It took time for designers to react to complaints about the design and improve it, but command reacted immediately to improper usage.

Commanders during reconnaissance standing near an IS-2 tank in a European city, winter-spring of 1945.

For instance, a memo titled "Directions on using IS-122 tank regiments and ISU-152 SPG regiments" personally signed by Marshal G.K. Zhukov was circulated within the 1st Ukrainian Front in May of 1944. The memo listed the typical ways of using heavy vehicles and also examples of "unskilled use of the IS and ISU that led to senseless losses of these vehicles". This brief document was accompanied by a more thorough "Direction on the use of IS-122 tank regiments and ISU-152 SPG regiments in combat" composed by the Commander of Armoured and Motorized Forces of the 1st Ukrainian Front, Lieutenant General of the Tank Forces N.A. Novikov, which began with the following words:
"The use of IS-122 tank regiments and ISU-152 SPG regiments in tank and mechanized formations has a significant effect in combat, which is confirmed by the usage of these regiments within the 1st Ukrainian Front."

As further experience of the 1st Ukrainian and other Fronts showed, the "significant effect in combat" was retained until the very end of the war.

Original article by Andrey Ulanov.


  1. I though there was an exit hatch for the driver on the bottom of IS-2..? (Ạlthough if the fuel tanks he's sitting between get hit, catch on fire, and leak, the ground underneath the tank will be ablaze too, eliminating that as an exit).

    Excellent article. It makes sense the greatest vulnerability of the IS-2 was its low rate of fire (hence, surround it with things that do fire faster). This tank is better employed in longer-range overwatching roles where its armor offers excellent protection than being the spearhead of an attack. Conversely, the Germans best shot at dealing with this tank would be to engage it at very close "can't miss" ranges where their superior rate of fire should be decisive. This would even true for King Tigers, despite the misinformed protests of Wehrmacht fanboys.

    Oh, and I see the reference against "penny packeting" these assets. Tanks in mass actually protect each other much better, they're much more likely to be lost if used in ones and twos and threes. It's also not surprising that commanders turned into "pack rats"; in fact, while the US Army was supposedly based on achieving a flexible "combat mission" assembly of assets for any given situation, in actual practice US divisions too turned into "pack rat" collections which included so-called "independent" units like TD and tank and artillery battalions that more-or-less stayed permanently attached to the division.

    1. There was an evacuation hatch, but you had to unlock 4 latches to open it. If your tank is on fire, you probably don't have the time for that.