Object 701-5, the last 122mm S-34-II armed IS-4 Prototype

Would you like to see the Object 701-5 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 another IS-4 Prototype! This is the Object 701-4!

The Object 701-5 parked on a snowy road

Quick note:

The name Object 701-5 is more an English version of the original name of the tank. The actual name is Объект 701 № 5.
As you can see in Russian the Prototypes are given a number, and this one is Number 5. But on the English side of the internet the 701-5 seems to be more widely used. And me having to constandly say Number 5, or No 5 might get a bit confusing. So I’m using Object 701-5 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 sixth 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 701-5) kind of started out at the Object 701-1. In a way tho. When the Object 701-1 was done being used for tests, she was taken apart and re-build into the Object 701-5. A hard factory reset if you will.

Object 701-5 in travel position

Just like the previous Prototype (The Object 701-4) this tank had all the most recent Armour Upgrades, and was armed with the 122mm S-34-II gun.

The 122mm S-34-II was an experimental gun based on the 100mm S-34 gun. It was made as replacement for the D-25T. The S-34-II had a few big improvements compared to the D-25T:

  • The gun was more rigid and allowed for more accurate fire.
  • The lack of a muzzle brake reduced the size of the smoke comming out of the gun when firing, and also made it safer for infantry to be standing next to the gun when firing.
  • The gun was fitted with a projectile rammer which increased the rate of fire.
  • A device was fitted that would blow air through the gun after it had fired, which reduced gas contamination inside of a tank turret.

So with all those improvements, why was the gun not used on any other tanks? Well that is because this gun required the gunner to be on the right of the gun, and the loader on the left. And on all other tanks with the D-25T it was the other way around. So this would have required a redesign for any tank that wanted to use this gun. And in the end it was cheaper to use the D-25T instead of redesigning all tanks with 122mm guns fitted.

On November the 29th, 1944, the tank was prepared to be shipped out to Kubinka where she would be going through the usual Prototype Tank tests. And on the 16th of December she arrived. The next day the tests began and would be finished on the 24th of January.

The tank succesfully passed the 1000km driving tests. It drove a total of 1051km, 405 of which were done on an asphalt road, and 623 on a rough track with obscacles. She did all this while being fully loaded with ammunition, a full set of tools and spare parts, just as if she was going to war.
During one of the tests on an asphalt road she reached a top speed of 41,14km/h.

But just like any Prototype being tested, not everything can go well. The tank also experienced some issues regarding the turbo charger for the V12 engine, which was due to an error by the driver.
Futhermore there were some small oil leaks, small breakdowns regarding the brakes and transmission gears, but in the end nothing that couldn’t be fixed on the spot. Unlike the previous Prototype (The Object 701-4) who decided to blow out it’s own transmission and get stuck in a field!

Object 701-5 driving up a hill

The final fate of this tank is not really known, but considering it’s not currently sitting at the Kubinka Tank Museum, I think it’s safe to say she was scrapped. Most likley to re-use some of it’s more expensive parts. Or maybe even it’s hull was used for any of the future built IS-4’s, who knows.



I would love to see this, or any other, IS-4 Prototype ingame. This specific one is very well documented and we got tons of photos of her, so it’s a perfect pick to add to the game.

This one being almost like the IS-4M we have ingame (Armour wise that is) makes me think of it as a good techtree or premium vehicle. 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 701-5 <|> IS-4Minnmm

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

Main armament
122mm S-34-II <|> 122mm D-25T
Vertical guidance
-3° to +19° <|> -3° to +19°
Rate of fire (Rounds per minute)
2,3 - 4 <|> 2,2 - 3

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

Turret armour
~400mm <|> ~400mm
200mm <|> 250mm
200mm at 20° <|> 200mm at 35°
200mm at 30° <|> 170mm at 35°
30 - 45mm <|> 30 - 50mm

Hull armour
Frontal Upper Glacis
140mm 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
100mm at 37° <|> 100mm at 37°
Rear Upper Glacis
120mm at 32° <|> 100mm at 32°
Rear Lower Glacis
120mm at 40° <|> 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 701-5.



General outlines of the Object 701-5

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: 122mm S-34-II gun
    • Vertical guidance: -3° to +19°
    • Rate of fire: Around 3-4 rounds per minute
    • Ammunition storage: 30 rounds
    • Ammunition types: Most likely the same as the D-25T, just not the post war BR-471D round.
  • Secondairy armament: 7.62mm DT machine gun


  • Turret:
    • Mantlet: 400mm effective armour when hitting it above the barrel
    • Front: 200mm at various angles
    • Sides: 200mm at 20°
    • Rear: 200mm at 30°
    • Roof: 45mm

  • Hull:
    • Frontal Upper Glacis: 140mm 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: 100mm at 37°
    • Rear Upper Glacis: 120mm at 32°
    • Rear Lower Glacis: 120mm at 30°
    • Engine Deck: 30mm
    • Bottom: 28mm

** = It’s possible that the armour was thinner at 140mm thick at the rear around the transmission. Something like this is mentioned in a source but is not very clear about it.

Ammunition layout of the Object 701-5

Extra blueprints:


Top view of the turret layout

Detailed drawing showing the visibility ports on the tank

Detailed drawing showing the visibility ports on the tank*

Side photo of the Object 701-5 parked on a snowy road

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, this one is armed with a 100mm gun!
  • 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
  • Object 701-6, this is the pre-production IS-4.

More photos




Primary source:

Secondairy sources:

Extra sources:

S-34-II gun: