KV-13 (1943), Tiger's least known victim.

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KV-13 improved
KV-13 (1943), IS-1 or 233 (note that “object” was still not used). In the ChKZ courtyard, March 1943.

This is the improved model from my previous suggestion of the original KV-13. And the direct predecessor to the IS-1. Though the name IS-1 was already in use for the previous model. It became more prominent during testing of this vehicle. However, to not confuse it with the production IS-1, I propose that it be called KV-13 (1943). But I will often refer to it as the improved KV-13 in this suggestion.

Much like the KV-13 (1942), it would be a heavily armoured vehicle with an anemic gun (F-34) and can be compared to other heavy tanks such as the M4A3E2. Though it would trade some of the armour for better mobility. Compared to the KV-13 (1942) this improved model would gain both turret armour (100mm vs 85mm) and side hull armour (100/90mm vs 85/75mm), as well a new crew member, at the cost of mobility. Though it would still be very fast at 16.2hp/t. Much like the KV-13 (1942), I doubt this vehicle fits the tech tree. But there’s plenty of ways it could come to the game.

Developmental history

See history

The vehicle’s history goes as far back as that of the original KV-13, obviously. The design was a successor to the KV-1. But unlike the earlier attempts at a successor, which focused solely on creating bigger and heavier variants of the KV-1. Most of which were known under the name KV-3 (or even KV-4) at various points, these were the T-150, T-220, T-221, T-222 and T-223. The KV-13 was the first design to focus on the issues plaguing the production KV-1. Which, mainly, was its weight.

T-150. The first attempt at a beefier KV-1.

T-220. Enlarged KV-1 in order to fit an 85mm gun.

T-223. Never built, but essentially the T-220, but with a 107mm gun.

Originally work started on decreasing the weight of the in production KV-1 through various compromises. This became the KV-1S. During development of the KV-1S the efforts were split into also creating an entirely new vehicle. This was the KV-13. The KV-13 was slightly smaller, weighed significantly less, but still squeezed in more armour in the design than the KV-1.

KV-1S September 42
Early KV-1S in September 1942.

Several of the developments of the time were shared between the KV-1S and KV-13. In both directions. While the KV-1S decreased the KV-1’s weight from 48 to 42 tonnes, the requirement for the KV-13 was far less at only 30 tonnes. Matching the T-34 at the time. A draft of the project was ready in May, 1942. But work on the vehicle stalled as the manufacturing plants were ordered to focus on KV-1 and KV-1S production, as well as an entirely new production line of T-34 at ChKZ. Thus a prototype wasn’t built until September. Even then it was done without authorisation.

KV-13 September 42
KV-13 (1942) in September 1942.

The fact that the vehicle tore itself apart during its maiden voyage in late September certainly didn’t change the minds of the higher ups. Even though several of its issues were worked on until the end of the year, it still didn’t meet some of the requirements that had been set. Such as a four man crew. The KV-13 had only a two man turret and a driver. Though a three man turret had already been designed. It was just never incorporated.

KV-13 3 man turret
KV-13 with three man turret designed in July 1942.

Work on the improved model officially started in November. Lessons from the first model obviously inspired the second. But as the KV-1S had also hit the frontline by this point, experience and criticism from the troops were also accounted for. The majority of improvements came to the automotive parts and engine compartment, and the three man turret was incorporated, but the armour was also slightly increased. Along with a host of smaller improvements for the crew. This all lead to it increasing in weight, now at just over 37 tonnes. Around 5 tonnes more than the original KV-13. Unlike the first KV-13, the improved model was not equipped with the 76.2mm ZiS-5 from the KV-1 and KV-1S, it was armed with the 76.2mm F-34 from the T-34. Why this was the case is not explained in any of my sources. Even the scale model was depicted with the ZiS-5. However if you know the history of the ZiS-5, it was essentially a development of the F-34 that copied all parts of the F-34… the biggest difference is the mantlet.

Object 233 model
Improved KV-13 scale model, December 1942. Notice the ZiS-5 gun mantlet.

The draft was done by December, but work on the prototype was stalled until late January, due to other priorities. This time it was caused by the KV-14, the early name for the SU-152. As its prototype had to be completed by the end of January. The improved KV-13 prototype wasn’t completed until March, 1943. At this point the KV-13 name disappeared, and was entirely replaced by “IS-1”. The tank suffered som issues. But it was far from the automotive failure the original KV-13 (1942) was. Still improvements were ordered to be made, and a trial batch of ten vehicles was even planned.

IS-1 inspection
The improved KV-13 prototype being inspected.

This plan would not come to fruition, as already in January, two Tiger Ausf.E tanks had been captured and sent to Kubinka, where trials showed the ZiS-5 and F-34 guns to be unable to penetrate its front armour at any range. Even its side armour could resist them. Urgently a better gun was requested in the new tank, which was formalised in May. The gun chosen was the 85mm 52-K anti-aircraft gun. But it was not like gun development had stood still this entire time, after all, the Tiger had been encountered on the eastern front already in August 1942. And in October, 1942, Factory No.92 had started work on an 85mm anti tank gun. The ZiS-25, which borrowed the majority of its parts from the ZiS-5. The ZiS-25 wasn’t perfect, and by May the requirements for the gun had been increased. As such the ZiS-25 simply served as the basis for yet another gun, the S-31.

A turret was designed that could mount the S-31. And fitted on both the KV-1S and improved KV-13. Although attempts were simultaneously also made to simply fit it into both of their regular turrets. But it was quickly realised either solution would be sub optimal. The turrets (and turret rings) were too small. Work on up-gunning the KV-1S continued which would result in both the object 238 and later object 239 (KV-85), but the improved KV-13 was instead ordered to be redesigned from scratch. One could almost wonder if the project had been cursed. But fear not, as the new redesign with increased turret ring and 85mm gun would become the famous (though short lived) IS-1 (object 237).

KV-13 85mm S-31
Blueprint of the new turret mounting the 85mm S-31 on the improved KV-13 chassis.

Object 238
Object 238. The S-31 stuffed into the turret of the KV-1S. This tank was built in summer 1943.

Already back in December 1942, another proposal had been made to equip the improved KV-13 with a 122mm howitzer, mirroring the KV-9 project which had met its demise in late 1942. This variant of the improved KV-13 received the index 234, and by Experimental Plant No.100 it got named IS-2.

IS-1 and IS-2 1943
The 234 (IS-2) and 233 (IS-1) next to eachother in March 1943.

Even though it shares both gun caliber and name with the IS-2. The two are completely unrelated other than how the improved KV-13 got reworked into the IS-1, which itself got reworked into the IS-2 (production). A common misconception of the 234 (IS-2) is that it used the turret of the KV-9. That is false. But its turret design was obviously heavily inspired by its predecessor. Attempts were also made to fit the 122mm D-12 howitzer into the turret of the improved KV-13, but this never materialised.

IS-2 improved turret
Blueprints of the 122mm D-12 fitted in the 233 turret.


Crew: 4


  • 76.2mm F-34* (See footnotes) (Ammo: 85)
    Elevation: -5/+25
    Sights: PT4-7 (2.5x Zoom, 26° FOV)
  • 7.62mm DT x3 (Ammo: 1920)


  • Weight (total): 37 160kg
  • Length (total): Unknown (Source needed)
  • Length (hull): Unknown (Source needed)
  • Width (total): Unknown (Source needed)
  • Height (total): Unknown (Source needed)
  • Turret ring: 1560mm


  • Engine: V-2K-13 (600hp) (16.2hp/t)
  • Transmission: Planetary
    forward gears: 8
  • Top speed: 55km/h


See armour

KV-13 1943 armour


  • Front: (Cast)
    Upper: 120mm at 30°
    Middle: 60mm at 72°
    Lower: 100mm at 40°
  • Sides: (Rolled)
    Shoulders: 100mm
    Upper: 100mm at 15°
    Lower: 90mm at 0°
  • Rear: (Rolled)
    Upper: 60mm at 49°* (See footnotes)
    Lower: 60mm at 40°
  • Floor: (Rolled)
    Front: 30mm
    Rear: 20mm
  • Roof: (Rolled)
    Rear: 20mm

Turret: (Cast)

  • Front: 100mm
  • Sides: 100mm at 15°
  • Rear: 100mm at 30°
  • Roof: (Rolled)
    Front: 30mm at 85°
    Rear: 30mm at 90°


See footnotes
  1. One source claim it uses an F-34M cannon. I don’t know what would make the F-34M different from the F-34. Either way it certainly wouldn’t perform different in game.

  2. Regarding the rear armour plate angle. I can only make out 49 degrees on the diagram in source 12, but I remember another source stating 45 degrees. I’ll just leave it as being unclear what angle the rear upper plate was mounted at for now.

Other images

See images

Object 233 side
Side profile of KV-13 (1943).

Object 233 Rear
Rear of KV-13 (1943).

Object 233 blueprint
KV-13 (1943) blueprint from December 1942.


  1. https://dzen.ru/a/X_94ZP2nolPThdf2?sid=103043105549737345

  2. Tank Archives: Less Armour, More Mobility

  3. Tank Archives: Unlucky KV

  4. https://dzen.ru/a/X226CzqjnkOqxz6d?sid=343455091904197401

  5. Tank Archives: Second to Last Step

  6. Tank Archives: IS, First Series

  7. Tank Archives: IS #1 and #2

  8. Tank Archives: SU-152: From Assault Gun to Tank Destroyer

  9. Tank Archives: Howitzer KV

  10. Tank Archives: The First Coming of the IS-2

  11. Tank Archives: Failed Modernization of the KV-1S

    1. A. G. Solyankin, M. V. Pavlov, I. V. Pavlov, I. G. Zheltov (2005) Отечественные бронированные машины. XX век. 1941–1945. (Eng. Domestic Armored Vehicles. XX Century. 1941–1945). Exprint.
1 Like

Very nice post. Well Done.

Where would it sit in the tech tree? What BR?

1 Like

I don’t think it’s quite suited for the tree as there’s already plenty heavy tanks where it would be placed, not to mention unfriendly to users. Though not unsurprisingly the poll leans towards the tree.

I think 5.0 would be the best spot for it, it’s miles faster than the KV-1 ZiS-5 and with more armour to boot, though with bigger turret weakspots. If too powerful there, 5.3 would be an option.

I get your point. It is possible that if Gaijin doubled up on tanks, then it might give players a different path to take or maybe even more options at a certain BR . For example, without Premiums I only have one Russian tank at 3.3. The T34 the others are 3.0 or 3.7.

I’d love to see the KV-13, but I honestly have no clue what BR it would even fit in. It’s basically a better armored and faster IS-1 with a 76mm gun. It’d club low tiers pretty hard, but unless it has APCR its not going to be able to do anything against Tigers.