I believe that this system, which has greater mobility and fire maneuverability than the B-4 howitzer, can be successfully employed against concrete bunkers using direct fire.
The backwards movement of the howitzer can be eliminated by placing wooden blocks under the tracks.
I propose ordering a batch (several dozens) of these auxiliary-powered howitzers to be manufactured in August of this year. A production run of that size would be entirely realistic.{12}
The letter forwarded a draft State Defense Committee decree “on the manufacture of a batch of B4-S51 auxiliary-powered 203 mm howitzers” that would clear the way for production of the S-51 in the event of a positive decision. The name of the person meant to sign the decree was not indicated, but Stalin usually put his own signature on decisions of that type.
1. Accept the B4-S51 203 mm auxiliary-powered howitzer developed by the Central Artillery Design Bureau of the People’s Commissariat of Arms with the traversing mechanism of the B-4 203 mm field howitzer model 1931 mounted on a KV-1S tank chassis for service with the Red Army.
2. The People’s Commissariat of the Tank Industry (Comrade Malyshev) and the Main Tank Repair Directorate of the Red Army (Comrade Sosenkov) shall deliver 50 reconditioned KV-1S tanks minus turrets and with running gear, engines (with no more than 10% of their operating hours used), transmissions, and complete field SPT&A kits in good working order to the People’s Commissariat of Arms by the following deadlines:
By August 10: 25
By August 25: 25
3. The People’s Commissariat of Arms (Comrade Ustinov) shall, by August 10 of this year, manufacture adapters and mounting parts using drawings produced by TsAKB and organize production engineering for the B4-S51 203 mm howitzers by the following deadlines:
By August 20: 20 auxiliary-powered howitzers
By August 30: 30 auxiliary-powered howitzers
4. During production, eliminate flaws with the 203 mm howitzer installation identified during proving-ground tests by requiring TsAKB (Comrade Grabin) to make the necessary changes to the drawings and submit them to the Red Army’s GAU for approval by August 1 of this year.{13}
However, the decree was never signed. The repair plants were unable to provide the required number of repaired KV-1S chassis. Furthermore, chassis of that type were being used to manufacture recovery vehicles, which were urgently needed by armor units. In addition, the management of the Self-Propelled Artillery Office had a large number of questions about the S-51, as did Malyshev. Malyshev (People’s Commissar of the Tank Industry), Ustinov (People’s Commissar of Arms), Fedorenko (Main Armor Directorate), and Yakovlev (Main Artillery Directorate) came together for a meeting in late July 1944. Malyshev and Fedorenko were strongly opposed to manufacturing the S-51. Their argument was that the SP gun was obviously overloaded and could not sustain long-term use.
Meanwhile, TsAKB continued working on heavy SP guns. In the summer of 1944, the design bureau built the S-59—an SP gun armed with the BR-2 152 mm heavy gun. To make it, TsAKB used a repaired KV-1S with hull serial number 30164 and engine number 309512 that had been provided by Repair Plant No. 1 on October 29, 1943. Few modifications were made because the same components were used for both the BR-2 and the B-4. According to the documentation, the S-59 was accepted for proving-ground tests in late August 1944.
However, the tests performed on the S-59 were largely academic because the KV-1S chassis had been rejected. The logical solution, which was settled on in late June 1944, was to replace the KV-1 chassis with an IS. Also, on July 29 the Leningrad branch of TsAKB proposed mounting the BR-17 210 mm gun or the BR-18 305 mm howitzer on a T-34 tandem tank chassis. This project was developed as an alternative solution. According to documentation, People’s Commissar of Arms Ustinov proposed drawing up an operational requirement for that vehicle, but it did not advance beyond the conceptual design stage.
On August 14, the chairman of the GAU’s Artillery Committee approved an operational requirement “for a 203 mm auxiliary-powered howitzer and a 152 mm auxiliary-powered gun based on the IS heavy tank.” The chassis replacement was not the only modification made to the future SP gun’s design. It was proposed that the vehicle be equipped with a turret-mounted DShK machine gun (with 1000 rounds of ammunition) for self-defense, and that it also have two DP machine guns (with 2520 rounds), four PPSh submachine guns (with 4000 rounds), and 25 F-1 hand grenades. The crew size was increased to 10, and the basic load from 12 to 15 rounds for the B-4, or 25 rounds for the BR-2.
On September 22, GAU chief Marshal of Artillery Yakovlev wrote a memorandum for Beria. In the memo, he suggested that consideration be given to producing a modified version of the SP gun that would thereafter be based on the IS tank chassis. The report also clarifies some details regarding the revised project:
In my letter No. 623605ss of July 27 to you I reported on the issue of manufacturing a batch of 203 mm self-propelled howitzers developed by the TsAKB of the People’s Commissariat of Arms (Comrade Grabin).
As your response to my report instructed, I have discussed the matter in a joint meeting with the People’s Commissariat of Arms, the People’s Commissariat of the Tank Industry, and the Main Armor Directorate.
We decided that it would not make sense to mount a 203 mm howitzer on the KV tank chassis, given that there are insufficient numbers available and that doing so would overload it. We would be better advised to mount this howitzer on the IS tank chassis, which is currently in production.
Based on that decision, GAU has issued the People’s Commissariat of Arms and the People’s Commissariat of the Tank Industry an operational requirement for a 203 mm auxiliary-powered howitzer on an IS tank chassis, and the People’s Commissariats have issued appropriate orders to TsAKB and Factory No. 100 concerning project development.
The Main Armor Directorate has no requirement for this type of weapon for the armored forces and has expressed no interest in developing a 203 mm auxiliary-powered howitzer. On the contrary, it believes that it would be inadvisable to use an armored chassis for this purpose.
The People’s Commissariat of the Tank Industry is of the same opinion.
That opinion is hindering development of this weapon despite the formal order from the People’s Commissariat of the Tank Industry to Factory No. 100 to undertake the project.
The GAU fully agrees that armor as strong as that on the IS tank is unnecessary for an auxiliary-powered gun and, in proposing that the IS be used, is thinking of the opportunity it offers to rapidly acquire a weapon of this type based on a system currently in mass production.
GAU believes that there is an urgent need for 203 mm auxiliary-powered howitzers at this stage of Red Army combat operations.{14}
