Friday 17 September 2021

IS-4 Green Light

"State Committee of Defense Decree #5583ss
Moscow, Kremlin
April 8th, 1944

On production of experimental prototypes of a new heavy tank at the Kirov factory of the NKTP

The State Committee of Defense decrees that:

  1. The NKTP is permitted to produce two prototypes of a new heavy tank and one hull at the Kirov factory in April of 1944 and conduct trials of the tanks and penetration trials of the hull jointly with the GBTU.
  2. Approve the attached tactical-technical requirements.
  3. The People's Commissar of Tank Production (comrade Malyshev) and director of the Kirov factory (comrade Kotin) must focus on further improvement of the design and production quality of IS tanks and SPGs.
    Complete the necessary work for improving IS tank armour protection, transmission, and running gear within three months, using the experience of developing new heavy tanks to modernize IS tanks.
Chairman of the State Committee of Defense, I. Stalin

Attachment to decree #5583ss issued on April 8th, 1944
Tactical-technical characteristics of the Kirov factory heavy tank
  1. Type of tank: fully tracked
  2. Weight: 55-56 tons
  3. Crew: 4
  4. Dimensions:
    1. Hull length: 6520 mm
    2. Full length (barrel forward): 9700 mm
    3. Full length (barrel backwards): 8400 mm
    4. Width: 3220 mm
    5. Height: 2445 mm
    6. Clearance: 450 mm
  5. Armour:
    1. Upper front: 120 mm at 61 degrees
    2. Lower front: 160 mm at 29 degrees
    3. Lower side: 160 mm
    4. Side under the turret: 160 mm at 22 degrees
    5. Upper rear: 120 mm at 38 degrees
    6. Middle rear: 120 mm at 32 degrees
    7. Lower rear: 120 mm at 39 degrees
    8. Cast turret: 160 mm
  6. Armament:
    1. 122 mm cannon
    2. 7.62 mm DT machine gun
    3. 12.7 mm DShK machine gun
    4. 50 mm breech-loaded mortar
  7. Firing angles:
    1. Cannon and DT machine gun:
      1. 360 degrees horizontal
      2. +20 to -4 vertical
    2. DShK:
      1. 360 degrees horizontal
      2. Mounted for AA fire"


  1. I thought the IS-4 had 200 mm of cast turret armor all the way around (250 mm for the gun mantlet). I also recall 140 mm @ 61 degrees for the upper glacis, instead of 120 mm.

    But 160 mm @ 29 degrees for the lower plate, and side? 120 mm for the hull rear? That's a beast!

    1. These are the specifications for the first two prototype object 701's, which differed in several aspects to the final product.