Object 701-2, the 100mm armed IS-4 Prototype

Would you like to see the Object 701-2 ingame?
  • Yes.
  • No.
0 voters
How would you like to see it added ingame?
  • As a researchable vehicle.
  • As a premium vehicle.
  • As an event vehicle.
  • As a squadron vehicle.
  • I said ‘No’ in the first question.
0 voters

Hello everyone! Today I’m going to suggest a very unique IS-4 Prototype! This is the Object 701-2!

The Object 701-2 parked on the side of a road, note the 100mm gun with the muzzle brake

Quick note:

The name Object 701-2 is more an English version of the original name of the tank. The actual name is Объект 701 № 2.
As you can see in Russian the Prototypes are given a number, and this one is Number 0. But on the English side of the internet the 701-2 seems to be more widely used. And me having to constandly say Number 2, or No 2 might get a bit confusing. So I’m using Object 701-2 to be as clear as possible.

And incase you are wondering, there are seven total IS-4 Prototypes! From the Object 701-0 up to the Object 701-6!

With that out of the way, let’s continue!



The story of this tank began in 1944, she was the third IS-4 Prototype made. If you want to read more about the origins of the IS-4 Prototypes then check out my post on the first Prototype:

This tank (The Object 701-2) was made by the Kirov plant in the summer of 1944. This tank served as a test platform for futher testing of the Object 701, the biggest change that was tested on this prototype was the use of a 100mm gun instead of a 122mm one.

Compared to the previous two IS-4 Prototypes this one had some slight changes in the armour layout. Mostly some of the plates on the hull were more angled. We’re talking going from an angle of 20°, to 30°. Not a huge change but still something nonetheless.

A photo of the rear of the Object 701-2

The tank went out for testing on the 8th of July 1944. She managed to drive 492km over the course of her being tested. The average speed achieved by the tank during this time was 20,8 km/h. This was not the maximum possible speed, but just the speed the tank could get up to in normal situations.

Compared to the previous prototype (The Object 701-1), she did not go through as much driving trials. Instead the tank was used for firing trials for the 100mm gun, and later for live firing trials.

To explain the live firing trials bit I’ll first have to explain a little bit about the prototype that was build after this one. The Object 701-3.
The Object 701-3 was build to the same design as the Object 701-2, but it was given different side armour. Instead of the 160mm of side armour at a 30° angle, the Object 701-3 had 120mm at a 50° angle.
And so both the Object 701-2 and Object 701-3 were to be used for live firing trials to see what results the different side armour layouts had.

For this purpose the Object 701-2 had her turret removed, and her hull would be fired upon by various guns. Both captured German guns and Soviet guns.

Two photos of the hull after the firing trials

The results of the firing trials showed that the 160mm plate at an angle of 30° (What was fitted to the Object 701-2) proved to be superior against armour piercing shells. And the 120mm plate at an angle of 50° (What was fitted to the Object 701-3) was superior to sub-caliber shells.

After the tests were done the tank was taken apart, and it’s parts re-used for the last IS-4 Prototype, the Object 701-6.



I would love to see this, or any other, IS-4 Prototype ingame. This one being armed with a 100mm gun, on a heavily armoured late WW2 hull…that is just amazing! The high fire-rate combined with a russian heavy tank is something we don’t have a lot of ingame.

I think this tank would make for an amazing techtree vehicle, being put in a folder with the IS-4M maybe. But let me know what you think in the poll above!

To wrap things up let’s compare this one to the ingame IS-4M:

Object 701-2 <|> IS-4Minnmm

4** <|> 4**
750hp V12 <|> 750hp V12
Suspension Type
Torsion bar <|> Torsion bar

Main armament
100mm S-34-I*** <|> 122mm D-25T***
Vertical guidance
-3° to +19° <|> -3° to +19°
Rate of fire (Rounds per minute)
2,5 - 8 <|> 2,2 - 3

Secondairy armament
mmmi7.62mm DT <|> 2 x 12.7mm DShK

Turret armour
~400mm <|> ~400mm
160mm <|> 250mm
160mm at 20° <|> 200mm at 35°
160mm at 30° <|> 170mm at 35°
30 - 30mm <|> 30 - 50mm

Hull armour
Frontal Upper Glacis
120mm at 61° <|> 140mm at 61°
Frontal Lower Glacis
160mm at 45° <|> 160mm at 45°
Upper Sides
160mm at 30° <|> 160mm at 30°
Lower Sides
160mm at 0° <|> 160mm at 0°
Rear plate above the Transmission
120mm at 37° <|> 100mm at 37°
Rear Upper Glacis
120mm at 32° <|> 100mm at 32°
Rear Lower Glacis
120mm at 30°**** <|> 100mm at 40°****
Engine Deck
30mm <|> 30mm
30mm <|> 30mm

** = On the IS-4M the gunner and commander sit to the left of the gun and the loader to the right. This is swapped on the Object 701-2.
*** = Both guns have different benefits and downsides. It just depends on what you prefer, firerate or caliber.
**** = These two armour layouts both amount to almost the same effective thickness, but a plate at a higher angle has a higher chance to ricochet an incomming shot.



Armour layout of the Object 701-2, the bottom left drawing is the Object 701-2, bottom right is the Object 701-3

Basic stats:

  • Crew: 4 (Commander, Driver, Gunner, Loader)
  • Powerplant: 750hp V12
  • Suspension Type: Torsion bar
  • Turret traverse while targeting: 7,5 degrees/second
  • Maximum possible turret traverse: 15 degrees/second


  • Main armament: 100mm S-34-I gun
    • Vertical guidance: -3° to +19°
    • Rate of fire: Around 5-8 rounds per minute
    • Ammunition storage: 41 rounds
    • Ammunition types: APHEBC and HE. Same as the Object 248 ingame
  • Secondairy armament: 7.62mm DT machine gun


  • Turret:
    • Mantlet: 400mm effective armour when hitting it above the barrel
    • Front: 160mm at various angles
    • Sides: 160mm at 20°
    • Rear: 160mm at 30°
    • Roof: 30mm

  • Hull:
    • Frontal Upper Glacis: 120mm at 61°
    • Frontal Lower Glacis: 160mm at 45° + spare track links
    • Upper Sides: 160mm at 30°
    • Lower Sides: 160mm at 0°
    • Rear plate above the Transmission: 120mm at 37°
    • Rear Upper Glacis: 120mm at 32°
    • Rear Lower Glacis: 120mm at 30°
    • Engine Deck: 30mm
    • Bottom: 30mm

Another blueprint of the armour layout of the Object 701-2

A side profile of the Object 701-2, with the turret facing backwards

That is all for now! Hope you enjoyed reading about this unique prototype.

Make sure to leave a vote in the poll above!

Also be sure to check out all the other IS-4 Prototypes I’ve suggested:

  • Object 701-0, this is the first IS-4 prototype.
  • Object 701-1, this one has a 50mm mortar added.
  • Object 701-2
  • Object 701-3, this was used for firing trials. (This thread is not a suggestion, but just a normal post)
  • Object 701-4, this was one of the last IS-4 prototypes
  • Object 701-5, this is the last IS-4 prototypes with the S-34-II gun.
  • Object 701-6, this is the pre-production IS-4.



Primary source:

Secondairy sources:

Extra sources:

S-34-I gun:



With much less armor, especially in front, will this be much lighter than IS-4?

When you look at the armour side by side, the Prototype IS-4’s are not that much lighter then the Production IS-4. But in the end, yes they are a little bit lighter.