High powered SPGs came up again in late 1939. While storming the Mannerheim Line, the Red Army needed an SPG with a high caliber gun and at least light anti-shell armour. In the middle of December of 1939, the Kirov factory and factory #185 design bureaus received an order from the Military Council of the North-West Front to develop engineering tanks with anti-shell armour. Factory #185 started two projects at once. Work began on an SPG based on the T-100. Additionally, it was decided to equip the SU-14 with armour. You would assume that the already made SPG was the faster solution, but no, work only competed on March 20th, a week after the end of the Winter War. The creation of an SPG on the T-100 chassis was not fast either, resulting in a vehicle named T-100Y, armed with a 130 mm B-13 naval gun.
The Kirov factory took a different route. In January of 1940, a prototype of the KV heavy tank (serial number U-0) arrived from the front. According to orders from the Military Council of the North-West Front, the first 4 tanks, including U-0, were to be equipped with 152 mm howitzers to defeat pillboxes. An enlarged turret was rapidly developed as a result. Work on the enlarged turret was done by SKB-3, headed by N.V. Kurin. Initially, the 152 mm model 1909/30 howitzer was planned, indexed L-21. In metal, the assault KV was equipped with a shortened M-10 (indexed MT-1). By February 10th, the new U-0 passed gunnery trials, and by February 17th, U-0 and U-1 were sent back to the front. "KV with large turret" tanks first saw battle on February 22nd. By March 3rd, there were 4 tanks of this type on the front lines.
Due to the results of the Winter War, it was decided that the "bunker buster" theme would be continued. During the spring and summer of 1940, the Kirov factory and factory #185 continued designing heavy SPGs on the T-100 and SMK chassis. However, the final fate of these vehicles was decided by the end of June. Based on the results of trials, it was clear that neither tank will be mass produced, since the KV was more protected and weighed less. The "KV with a large turret" was an adequate interim solution for the bunker buster problem.
As mentioned above, the "KV with a large turret" was a temporary answer to the need for a heavy assault SPG. Kurin's tank was a hypertrophied support tank like the artillery BT-7 (frequently called BT-7A, but that index belongs to another tank). The vehicle on the KV chassis (indexed KV-2 in 1941) had the advantage of parts commonality with its base vehicle. However, it had many drawbacks. The chassis allowed for a limited power gun, while the military demanded that the Br-2 gun be used. Due to the limited size of the turret, loading the M-10T was no easy task. The presence of a rotating turret did not mean that the tank could shoot from any angle.
After the SMK and T-100 projects died, efforts were concentrated on the creation of a heavy tank that was a modernized KV. On July 17th, 1940, the Committee of Defense of the Council of People's Commissars issued decree #198ss on the creation of new vehicles on the KV chassis. According to the decree, the Kirov factory was to develop the following:
- Two experimental KV tanks (T-220) with 100 mm armour. One was to be armed with the F-30 85 mm gun, the other with the F-32 76 mm gun.
- Two experimental KV tanks with 90 mm armour. One was to be armed with the F-32 76 mm gun, the other with the F-30 85 mm gun.
- One experimental SPG with a Br-2 152 mm gun.
The KV with 90 mm of armour received the factory index "150" (GABTU correspondence used the index T-150). It differed from its base vehicle in its 76 mm F-32 gun and a commander's cupola. It was planned that this tank, under the index "KV-3" will replace the KV-1.
The "220" tank was more distinct from the KV-1. The tank had a longer hull; the amount of road wheels increased to 7 on each side. The T-220 had a new turret, which housed the 85 mm F-30 gun. The tank used an 850 hp V-2F (V-10) engine. It was completed on December 5th, 1940.
The technical requirements for the 152 mm SPG were finalized by the end of August of 1940.
The SPG that the Kirov factory was tasked with received the index of "212". The chief engineer for this project was T.N. Golburt. The 212 was reminiscent of the SU-14-1, especially when it came to the layout of the fighting compartment. The chassis was a reworked T-220 suspension, with an engine in the middle and drive wheels at the front. The front also housed the driver's compartment. The fighting compartment was in a large casemate at the rear of the hull. On one hand, this design increased the size of the SPG. On the other, it increased crew comfort. The rear position of the casemate also reduced the distance that the Br-2 stuck out past the vehicle's hull.
2 million roubles were issued to this project. 100,000 went into the development of the technical project, 25,000 to the design of a model, 300,000 on blueprints, 75,000 on blueprint edits, 1.1 million on the production of a prototype, 100,000 on trials, and then 300,000 on repairs. The cost of the armament was not included in this sum.
The first prototype was due on December 1st, 1940, but serious corrections had to be made due to faults found during the design process. According to a GABTU report on experimental works, some components for the 212 were produced by January of 1941. Also, the technical project was completed, and sent to the Izhor factory for the production of a hull. By then, 1.5 million roubles have been spent. Work was going slowly due to higher priority of the T-150 and T-220, as well as other problems.
The hull for the new SPG was received only on March 5th, 1941. According to reports, assembly was stalled due to a lack of ready components. By the spring of 1941, the 212 project was dropping in priority at the Kirov factory. The factory received an urgent order for a heavy tank that inherited the T-150's index of "KV-3". The project, indexed "223", was developed on the T-220 chassis, with a front plate thickened to 120 mm and a new turret for the 107 mm ZiS-6 gun. The mass was estimated at 68 tons. The design of this vehicle began after learning of a new German heavy tank. Due to this load, work on the 212 stalled starting in the second half of March of 1941. April and May reports on experimental work state "No changes" in the row titled "self-propelled gun on the KV chassis".
After Germany's attack on the USSR, designs were reconsidered. Work on some designs was accelerated. Others, either in the initial stages or not compatible with the realities of modern war, were cancelled. According to the most common version of this story, this was the fate of the 212, but it did not happen quite this way.
According to order #253ss of the People's Commissariat of Heavy Production, the KV-3 was transferred from the Kirov factory to the Chelyabinsk Tractor Factory (ChTZ). Engineers, technologists, and materials were sent to Chelyabinsk. One KV-3 made it to the front, another, without a turret or components, was sent to Chelyabinsk. In February of 1942, this KV-3 was assigned to the experimental OP-2 plant. As for the 212, until the start of August of 1941, it was still at the Kirov plant. Only then was it transferred to the Ural Factory of Heavy Machine Building (UZTM in Sverdlovsk, modern Ekaterinburg).
Meanwhile tank production had no time for the KV-3, nor a bunker buster on its chassis. The Kirov factory was evacuated to Chelyabinsk and renamed Kirov Factory in Chelyabinsk (ChKZ), and the Izhor factory that made KV armour was sent to Sverdlovsk. UZTM was renamed to Izhor factory, and only got its name back on January 4th, 1942. UZTM was also loaded with Ordzhonikidze factory #37 and Kalinin factory #8 setting on up its territory. Factory #75, which was producing the V-5 engine was moved to Chelyabinsk, and began working on the much more necessary V-2. The situation with 152 mm guns was no better. The last Br-2 was produced by Barricade factory #221 (Stalingrad, modern Volgograd) in 1940.
Bunker busters fell out of priority, but not for long. In November of 1941, work restarted on many prototypes referred to in the SNK report "On self-propelled artillery" from May 27th, 1941. Nearly all of these projects remained in the requirements stage until 1942, there was not even a possibility of a design. Most factories tasked with designing the SPG were either busy with setting up manufacturing in the buildings where they were evacuated to in the summer and fall, or loaded with more urgent requests. Nevertheless, the list of experimental works for 1942 once again included the KV-3, scheduled for completion on May 1st, 1942. The same was true for a "two-stroke 1200 hp diesel engine" (due on October 1st, 1942), "charging the V-2 engine to 1200 hp" (due on July 1st, 1942). In March of 1942, the topic of "152 mm SPG on the KV-3 chassis (bunker buster)" resurfaces. The KV was indicated as its chassis, and the oscillating part of the Br-2 its armament. Factory #100 was listed as responsible for the chassis. Factory #8 was responsible for the gun. 1.5 million roubles was issued for this project. A prototype was expected by July 1st, 1942. However, the KV-3 was dead and buried in spring of 1942, and different vehicles were considered candidates for a bunker buster chassis.
Read more about the Object 212 and other SPGs on the KV heavy tank chassis in the book "SU-152 and other KV-based SPGs", published by Tactical Press.
Article author: Y. Pasholok.
Original article available here.