Monday 14 October 2019

ISU-122S Acceptance

"State Committee of Defense Decree #6430ss

August 22nd, 1944
Moscow, Kremlin

On the acceptance of the ISU-122S SPG with the 122 mm D-25S gun into service and into production 

The State Committee of Defense decrees that:
  1. The ISU-122S SPG with a 122 mm D-25S gun designed by factory #9 in accordance with the tactical technical characteristics in attachment #1 is accepted into service.
  2. The People's Commissariat of Tank Production (comrade Malyshev) and People's Commissariat of Armament (comrade Ustinov) must correct the defects discovered both in the gun and in the SPG during trials and produce a pilot batch of 25 units before September 1st 1944. Produce the required blueprints by the same date.
  3. The GABTU (comrade Fedorenko), GAU (comrade Yakovlev), People's Commissariat of Armament (comrade Ustinov) and People's Commissariat of Tank Production (comrade Malyshev) must put one of the pilot ISU-122S SPGs with a 122 mm D-25S gun through mobility and gunnery trials.
  4. Install the TSh ball socket sight on the ISU-122S SPG with the D-25S gun.
    To fire indirectly install the same panoramic sight and carrier as used on the SPG with the D-10S gun.
    The NKV and NKTP must develop the installation of a mechanical sight coupled with the PG panoramic sight by August 30th.
  5. The NKTP (comrade Malyshev) and Kirov factory (comrade Zaltsmann) must prepare for production of the ISU-122S SPG with a D-25S gun with the aim of producing 25 vehicles in August, counting towards the overall count of SPGs delivered.
  6. The NKTP (comrade Malyshev) and Kirov factory (comrade Zaltsmann) must produce 250 IS tanks and 250 ISU-152/ISU-122 SPGs per month starting in August of 1944.
  7. The NKV (comrade Ustinov) and factory #9 (comrade Gonor) must begin producing 122 mm D-25S guns and deliver 50 D-25S guns in August of 1944.
  8. The NKV (comrade Ustinov) and factory #9 (comrade Gonor) must produce no fewer than 50 122 mm D-25S guns monthly.
  9. The GAU (comrade Yakovlev) and and NKV (comrade Ustinov) must provide the NKTP with TSh sights according to the schedule of production of the ISU-122S with D-25S gun.
  10. The NKTP (comrade Malyshev) and Uralmash factory (comrade Muzrukov) must produce 100 sets of all parts of the D-25S that differ from the D-25T, as well as frame mounts, by August 27th.
    After that, deliver sufficient parts for the D-25S to factory #9 for 50 guns per month, counting towards the D-25 gun quota.
    50 frames for the D-25S must be delivered per month, 50% of which should be mechanically finished. Reduce the quota for D-10S gun frame mounts by 25 per month.
  11. The People's Commissariat of Foreign Trade (comrade Mikoyan) must deliver the imported tools outlined in attachment #2 to the Kirov factory (Chelyabinsk) and Uralmash factory in the 3rd and 4th quarter, counting towards the government decrees for providing imported equipment.
  12. The Chief of the Main Directorate of Hydrolysis Industry (comrade Chuyenkov) must provide to the NKTP 100 extra tons of sulphite lye. The NKPS (comrade Arutyunov) must provide the transportation.
Chairman of the Committee of Defense, I. Stalin"


  1. Does this mean that by late 1944 German tank forces were less of a threat to Russia than reinforced positions. As such a cheap large well armored assault gun was more handy than a more costly tank of the same size but a reduced rate of fire due to it's cramped interior.

    1. If nothing else the ISU-122 had a gun better suited for tankbusting than the -152 mind you (flatter trajectory, faster reloading, etc.), and came to being largely because the production of ISU hulls exceeded that of 152 mm gun-howitzers to put into them.

      IIRC this thing didnt really have major RoF issues either; the fighting compartement had been designed with the much bulkier 152 mm in mind so they could throw a second loader into the spare volume which also meant the old screw breech, which had quickly proven too slow and cumbersome to operate in the IS turret, could be used without gutting the firing rate. Good thing too since replacing those with the sliding-block version in the heavy tanks had created a surplus of idle AFV-model 122 mm guns...

      Waste not want not.

    2. Perhaps that was what it was about. Plenty of idle big guns needing a home. Back when I was 18 a friend and I tried to give his old Buick a tune up and we forgot to save the firing order. After a while we got everybody involved and we all failed. Turns out the engine was not standard Buick . After several dealers we found a guy who explained that Buick that year had 20 spare tractor engines and just dropped them in cars. But he gave us the correct firing order.

  2. The 122mm D-25S was 46 calibers in length and had a higher muzzle velocity as opposed to the 122mm D-25T.

    1. This comment has been removed by the author.

    2. Actually, I would of said yes a few days ago but I just got ahold of some 1946 primary documents and it has the D-25T with a V0 of 795 m/s and the D-25C (which is S) as 781 m/s. I have to find out why are reversed from other sources.