Object 701-0, the first IS-4 Prototype!

Would you like to see the Object 701-0 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 the first Prototype of my favourite Heavy Tank. This is the IS-4 Prototype, Object 701-0!

A close up photo taken of the Object 701-0 while being tested in a field

Quick note:

The name Object 701-0 is more an English version of the original name of the tank. The actual name is Объект 701 № 0.
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 701-0 seems to be more widely used. And me having to constandly say Number 0, or No 0 might get a bit confusing. So I’m using Object 701-0 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 begins in July of 1943 when work began on the creation of a new Heavy Tank. This tank was meant to be built for the final stages of the Second World War, and the post-war period after that.

The first thing to be made of the new heavy tank was a wooden model. It was given the name Tank “K”. The model has 1944 IS-2 like hull and a narrow turret with a thick mantlet.

The wooden model of Tank “K”

The design was worked on more and eventually recieved an official Object number, this being Object 701. On the 10th of December 1943 the initial draft design of the tank was ready, and it would end up being approved in March of 1944 and the technical design blueprints were submitted.

The design was planned to be around 55-56 tons, a crew of four, an Diesel engine of 800-850 hp and a max speed of 40km/h on the road.

Armour would have been 120-160mm on the front of the hull, 150-160 on the sides and 120mm on the rear. Almost all the armour plates would be mounted on angles to futher increase the armour protection even more.
The turret would have been completely cast with an armour thickness of 150mm all around.

At last, armaments would have been a 122mm main gun, a 7.62mm DT machine gun paired with the main gun, and a 12.7mm DShK on the turret roof.

A wooden model of the Object 701.

The Kirov plant was given permission to built two prototypes of this tank in the shortest time possible. Later this was increased by two more hulls and turrets that could be used for live firing trials.
The first tank made, given the name Object 701-0 (Объект 701 № 0), was ready in April of 1944. From the 10th of April till the 24th the tank was put through trials and it drove a total distance of 1230km during that time.

The tank had 120-160mm of frontal armour (More details in the “Specifications” section), and was armed with a 122mm S-34-II gun, together with a 7.62mm DT.

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.

Futhermore the Object 701-0 was fitted with a planetary transmission that had six forward gears, and three reverse gears. And it seems to have done quite well.

Sadly this is it ends for the Object 701-0. After it came the Object 701-1 and 701-2, which would both continue to do more driving tests. With these two prototypes more issues regarding the engine and transmission arose. But as far as the Object 701-0 was concerned there is no specific note detailing these issues. I assume the tank was scrapped for parts quite early on and testing continued with the next prototypes.



I would love to see this, or any other, IS-4 Prototype ingame. They look really cool with that different turret and these Prototypes are the only tanks ever fitted with the S-34-II gun, so it’s the only way we can see that gun ingame!

This tank (The Object 701-0) is not the most unique of all the IS-4 Prototypes, but this one being the first one ever made does make it rather special. Also the tank has some very subtle differences in armour layout then the other IS-4 Prototypes, most make it easier to kill but hey it’s more unique that way! :P

I think this tank would make for a cool event 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 701-0 <|> 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
170mm <|> 250mm
170mm 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 20° <|> 160mm at 45°
Upper Sides
160mm at 21° <|> 160mm at 30°
Lower Sides
160mm at 0° <|> 160mm at 0°
Rear plate above the Transmission
120mm at 38° <|> 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 701-0.
*** = 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 701-0

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: 170mm at various angles
    • Sides: 170mm at 20°
    • Rear: 160mm at 30°
    • Roof: 30mm

  • Hull:
    • Frontal Upper Glacis: 120mm at 61°
    • Frontal Lower Glacis: 160mm at 20° + spare track links
    • Upper Sides: 160mm at 21°
    • Lower Sides: 160mm at 0°
    • Rear plate above the Transmission: 120mm at 38°
    • Rear Upper Glacis: 120mm at 32°
    • Rear Lower Glacis: 120mm at 30°
    • Engine Deck: 30mm
    • Bottom: 30mm

A side profile of the Object 701-0

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
  • 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, 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-II gun: