Saturday 7 December 2019

Kotin's Bobtail

In early 1943 the Red Army Main Armoured Vehicle Directorate (GBTU) and People's Commissariat of Tank Production (NKTP) agreed that the age of the KV-1S is coming to an end. Instead, the IS-1 (233), a further development of the KV-13, was to be produced in Chelyabinsk. This tank had the same firepower, but was more mobile and better protected. However, the experimental IS-1 was too unrefined and suffered from assembly issues. In addition, trials of the German Tiger tank showed that the Red Army was in need of a tank with an 85 mm gun. This was how the KV-85 was created, the last mass produced tank in the KV family.

A fast alternative to the IS

At first, the idea of modernizing the KV-1S was not discussed. According to the GKO decree "On production of IS tanks and SPGs at the Kirov factory", production of the KV-1S ceased in June of 1943. The ChKZ would switch to the SU-152 exclusively, producing 200 of them in June and 100 in July. This factory would also build the SU-122 (an SPG with the A-19 122 mm gun). Production stopped in July, and ChKZ was expected to produce 50 IS-1 and 50 ISU-152/122.

This proposal was declined. Instead, degree #3289 "On improving armament of tanks and SPGs" was signed instead. According to this decree, two prototypes each of IS-1 and KV-1S tanks with 85 mm guns would enter state trials on July 1st, 1943. Work on the 85 mm tank gun began in March of 1943 and showed that significant changes to the tanks were required.

D-5T-85 gun in the IS-1 turret.

The design of an 85 mm gun with the ballistics of the 52-K AA gun was a competition. The Central Artillery Design Bureau (TsAKB) was working on such a gun in Kaliningrad (modern day Korolyov). Their project was aimed at changing as little as possible in the chassis to speed up production. The turret was altered to improve crew conditions.

Factory #9 workers in Sverdlovsk took a different approach. Their design had radically different changes to both tanks, including the IS-1. It was clear during the development of the D-7 (later D-5T-85) gun that it would not fit into the existing IS-1 turret due to the small turret ring diameter. The first draft of the D-5T-85 called for a 1700 mm turret ring, towards May of 1943 it was clear that the turret ring must be even bigger, 1800 mm wide. This meant that the IS-1 chassis would have to be radically changed, but the Chelyabinsk factory was ready for this. The IS-1 would be changed anyway, and there was no point in building two different turrets for one gun.

The same gun from above. The compact design and wider turret ring meant that the crew conditions were better than in the KV-1S.

The first steps towards this tank with the index 239 were taken in mid-May of 1943. Starting with July this tank was called Object 239. The draft was ready by May 22nd. The lead engineer on this project was M.F. Balzhi. In addition to widening the turret ring many other alterations were made. The radio operator was removed from the hull, and the radio migrated to the turret. The fuel tanks were moved to the front of the hull. Calculations showed that the mass of the tank would grow to 46.5 tons. Deputy People's Commissar of Tank Production and Chief Designer at ChKZ Zhosef Kotin was in favour of this development, but in no hurry to announce it. Nevertheless, the NKTP insisted on production of a prototype. The second production KV-1S with serial number 15002 was chosen for conversion. The due date was set at June 25th.

By mid-June blueprints of the "1st variant with installation of the IS turret" were sent into production. At the time the F-85 (aka S-31) gun was selected due to delays with D-5T-85 development. The attitude towards this project is described in the following paragraph from the report on experimental work.
"It is worth mentioning that both the Kirov factory and factory #100 prioritized the modernization of the KV-1S behind the work on of the IS-2. Attention will be given to the aforementioned work after the IS-3 components and assemblies are complete, which has the highest priority at the moment."
Object 239, Chelyabinsk, late July 1943.

In reality the factory did not manage to meet the deadline not only for the Object 239, but also for the Object 237, or IS-3. The senior military representative placed the blame for this on the Kirov factory, which distanced itself from this work. Not a single turret was built for any of the tanks. As for the chassis, the first Object 237 was finished by June 30th.

In parallel, factory #200 finished the conversion of the KV-1S 15002 hull. The alterations were not too great. The radio operator's space was removed, as the driver's compartment was redesigned. The MG ball mount port was welded over, and the MG itself was moved to a fixed mount to the right of the driver. Bulges were added to the sides, and deflectors were added to protect the turret ring. Finally, the roof above the driver changed. Since the turret was enlarged, he no longer had a hatch, and had to climb out of the turret. To compensate, he received two MK-IV observation devices, which improved his vision. 

The welded over machine gun port is visible, as are the new observation devices above the driver's station.

By July 11th the factory had installed the running gear, fuel tanks, engine, and controls in the Object 239 hull. The turret was still not finished. In addition to the delays introduced by the Kirov factory, there was one single D-5T-85 gun built at the time. It was intended for installation into the Object 237 turret, which was completely assembled on July 8th. The newer tank still lacked a turret as of July 20th. The factory didn't wait for it to arrive, having completed the chassis and tested it over a 40 km run. Interestingly enough, the first D-5T-85 gun built still ended up in the Object 239 by the end of July.

All the changes increased the tank's mass to 46 tons.

The turrets of the Objects 237 and 239 were identical, which makes the mass difference all the more interesting. Object 237 weighed a little over 43.2 tons, Object 239 weighed almost 46 tons. However, it had its advantages. First of all, it had an impressive ammunition capacity: 70 rounds, compared to the Object 237's 59 and Object 238's (KV-1S with a stock turret and S-31 gun) 55. Secondly, as good as the IS-1 was, its production would take time, and the Red Army needed a tank that could fight Tigers now. The Battle of Kursk had just ended and only confirmed the low effectiveness of 76 mm guns against the newest German tanks.

The same tank from the rear.

Brief trials showed that the increase in mass had an effect on the tank's mobility. The average speed on a highway dropped to 16.4 kph, and off-road to 15.48 kph. The fuel expenditure increased to 409 L per 100 km. However, the chassis was not yet overloaded. The temperature of water in the cooling system did not go over 85 degrees, and the temperature of oil remained under 78 degrees. A slight decrease in mobility was not critical.

Changes to the hull were minor, which allowed the tank to replace the KV-1S in production.

The commission concluded the following:
"The commission considers it possible to recommend the KV-85 tank (KV-1S tank with partially altered hull and IS turret) for production instead of the KV-1S until IS tank production begins."

The final approval of the Object 239 was made after trials at the Gorohovets scientific research artillery proving grounds (ANIOP) conducted between August 21st and August 24th, 1943. It was clear that the D-5T surpasses the S-31 even before the firing began. The recoil length was only 240-300 mm, and the recoil brake was much easier to service. The turret of Object 237 was much more comfortable for the crew to work in, which improved the rate of fire. The Object 239 could fire at up to 10-13 RPM, which was twice as much as the Object 238.

Trials of the Object 239 at the Gorohovets ANIOP, late August 1943.

Trials at the Gorohovets ANIOP were more of an assurance than anything else. Stalin signed GKO decree #3891ss "On production of the KV tank with an 85 mm gun (KV-85)" on August 8th, 1943. This document confirmed that the Object 239 was selected. Production of the first 25 tanks was awaited in August. The advantages of the D-5 were demonstrated during the August trials of the SU-85 prototypes. Even though the D-5S-85 installed in the SU-85-II had a number of minor drawbacks, it was preferable to the design submitted by the TsAKB.

Object 239 after penetration trials, November 1943.

Trials of the Object 239 were not complete yet. First, the tank was submitted for reliability trials. In November of 1943 the tank was submitted for trials that changed its look. During trials of the PT8-15 sight, accepted into service as the TSh-15, the tank was hit by 76 mm proof and armour piercing shells fired from the ZIS-5 gun. The object of the trial was to determine the robustness of the system. The sight withstood being shot at from 300 meters, but the tank took some damage: the driver's hatch was knocked out and the commander's cupola was damaged. More trials awaited this tank, but those are best saved for another article.

Three months of worry

On August 12th the quota established by GKO degree #3891ss was reduced to 22 tanks. Even this small amount of tanks was not easy to produce. The factory had to wrap up KV-1S production, and, more importantly, produce 325 T-34 tanks, not including the SU-152, which had a higher priority than the KV-85. By August 26th no tanks had been delivered. The delivery was greatly expedited, and 16 tanks were accepted on August 31st. These bursts in productivity came at a cost. On August 31st a letter was sent to the GABTU from the senior military representative at ChKZ. He complained that a number of mistakes were made during the preparation of blueprints, which caused a dozen defects. Fuel tanks were modified by hand to be installed,  as were racks for electrical equipment. Instead of new Multicyclone filters the old Vortox were used. There were big problems with sights. Factory #9 also introduced issues, not having supplied counterweights. The tanks that were already accepted had to be redone. As a result, the first 5 tanks were delivered only by September 9th. In September ChKZ delivered 47 tanks, including the 22 built in August. 

Production KV-85, NIIBT, summer 1944.

Problems with the first production batch were mostly caused by subcontractors. Factory #200 began to ship hulls and turrets only on August 23rd. Factory #9 delivered the first 3 guns on August 28th, 17 on August 30th, and the last two in the morning of August 31st. There were other issues in addition to the counterweights that meant that more work had to be done on the guns. The situation repeated itself in September. As of September 19th only 6 tanks were delivered, 13 by September 24th. The factory had to once again rush to deliver the remaining tanks in the last days of the month. ChKZ made a delivery of 63 tanks, although not without issues. Problems with the aiming mechanisms were discovered. 
The tank was somewhat different technically from its prototype.

The poor situation with technical documentation earned the involvement of the NKTP and GBTU. On October 6th, 1943, a resolution was passed on the approval of technical documentation for the KV-85. The GBTU did not accept a number of blueprint groups, including the fuel tank racks, turret traverse mechanism, and the intercom. A number of blueprints were accepted provisionally, such as the fuel system, air filter, hull, D-5T gun and coaxial machine gun mount, electric trigger, and sight mount. 20 of these groups were identified, of which some had to do with the Object 237 that was supposed to replace the KV-85 as of November 1943. ChKZ didn't fully agree with the changes requested by the GBTU, but the design of the tank was slowly improved.

Due to the brief production run KV-85 tanks were nearly identical.

The plan for October was the same as for September: 63 tanks. Continued issues with subcontractors resulted in the same problems as faced in August and September. The first 3 tanks were delivered only on October 10th, 7 by the 17th, and only 20 KV-85 tanks by October 22nd. 56 were ready by October 56, the rest were rushed to completion. 67 KV-85 tanks were shipped in October, the remaining 34 were shipped in early November.

By then ChKZ had put the IS-85 into production. The first tank of this type was delivered on November 5th. This was also a temporary measure, as soon the IS-122 (IS-2) with a 122 mm D-25T gun replaced it.

The KV-85 was not fondly remembered. N.F. Shashmurin called this tank а "bobtail" in his memoirs, implying that its time was short. In his opinion, Kotin pushed it through as the simplest development of the KV-1S tank. Of course, memoirs should be approached critically, especially considering the complex relationship between Kotin and Shashmurin, but Nikolai Fedorovich's words are confirmed by some documents. The dramatic situation with the tank's production confirmed that Kotin's opinion regarding this modernization as the simplest solution was incorrect. Even a more or less ready chassis did not prevent issues with the transition from the KV-1S to the KV-85. 148 tanks produced over 3 months cost the factory staff a lot of worry.

Limited success

Major deliveries of the KV-85 began starting with late September of 1943. On September 23rd a train was sent to Kosterevo with reinforcements for the 27th Guards Tank Regiment. The tanks were sponsored by workers from Chuvashia and were a part of the "Chuvashian Kolkhoz Worker" tank column. The KV-85 was also shipped to the 7th, 14th, 28th, 30th, and 34th Guards Tank Regiments. The structure of these tanks was the same as for regiments equipped with the KV-1S. The TO&E authorized 21 tanks per regiment. This allotment remained until the end of the war. In early 1944 regiments armed with heavy tanks were renamed to Guards Heavy Tank Regiments.

This KV-85 in winter camo shows signs of active use. Winter 1944. 

The study of new tanks went at different rates. It was simplest for units that had already used the KV-1S, as the difference between the two was slight. However, some units were used to different tanks. For instance, the 34th Guards heavy Tank Regiment where 21 tanks were shipped on October 22nd, 1943, previously fought using Churchill IV tanks. Tankers of this unit had issues with the long gun barrel hitting trees. This regiment was the first to use the KV-85 tank in battle.

As it often happens, the first results were a mixed success. On November 20th, 1943, the 28th Army of the 4th Ukrainian Front was reinforced with the 34th Guards Heavy Tank Regiment and 40th Heavy SPG Regiment (with SU-152 SPGs). By 08:00 the regiments were prepared to fight. At 09:40 both regiments were given the order support the 9th Rifle Corps in its attack to break though the enemy's defenses, capture Malaya Lepetikha, and establish a crossing across the Dnieper. 20 KV-85 and 9 SU-152 took part in the attack. The SU-152 broke away from its infantry and ran into Ferdinand tank destroyers from the 653rd Tank Destroyer Battalion. The KV-85 attacked at the same time, but without infantry support their attack was also ineffective. The 40th regiment lost 6 SU-152s knocked out and 1 burned, the 34th regiment had 9 KV-85 tanks knocked out and left in enemy hands.

This tank was knocked out in late 1943.

The battle continued on the next day, and the Ferdinands counterattacked at 13:20. The SU-152 took their revenge, destroying 2 Ferdinands and 3 tanks. By the morning of November 22nd the 34th regiment had 9 battle ready KV-85s, the 40th regiment had 5 SU-152s, and 7 by the 25th. By the end of November 29th the regiment had 8 functional KV-85 tanks left. In this time the regiment destroyed up to 300 enemy soliders and officers, 2 anti-tank guns, 3 tanks, and 2 tank destroyers. Complete losses included 12 KV-85, 8 more were evacuated for repairs. 16 tankers died, 32 were missing, and 16 were wounded.

The SU-152 were more effective. Their unit claimed up to 250 infantrymen, 2 tanks, 9 SPGs, 18 anti-tank guns, 8 field guns, and 10 mortars. 4 SU-152 were lost irreparably, 6 were knocked out, but later repaired. 8 SPG crewmen were killed, 16 were wounded.

Considering the enemy of the new tank, the losses were not so horrible. Keep in mind that claims were exaggerated on both sides, and that a knocked out and burned out tank are two different things. The Germans like to recall only the battles of November 26-27th, claiming that 54 Soviet tanks were destroyed. Of them, 21 were claimed by the crew of Franz Kretschmer. However, the Iron Cross holder should have been more conservative. On November 26th the armoured forces of the 28th Army lost 8 tanks, of them only 5 were burned out, and on the 27th 25 in all. No matter how the losses are tallied, the number 54 cannot be obtained.

Captured KV-85 from the 34th Guards Tank Regiment, late November 1943. The tank was used by the 653rd Tank Destroyer Battalion.

The KV-85 faced Tigers too. The 7th Guards Tank Regiment received KV-85 tanks on October 28th, 1943. After restructuring in Tula, the regiment was sent to join the 60th Army of the 1st Ukrainian Front. The regiment went into battle on November 23rd, several days after the 34th regiment. The tankers took part in a defensive operation in the Kiev direction. On December 9th the bloodied regiment was transferred to the 38th Army. 9 KV-85 tanks remained by the end of January.

Their finest hour took place on January 28th, 1944. On that day, at 16:35, a group of 35 German tanks supported by infantry moved out towards the Telman sovkhoz farm. Soviet intelligence showed that the 1st SS Division was taking part in this attack. 60 men were defending the farm with 2 KV-85 tanks and 2 SU-122 SPGs in support commanded by Senior Lieutenant I.L. Podust. By Soviet data, the Germans lost 5 Tigers, 2 PzIVs, 3 PzIIIs, 7 APCs, and 6 anti-tank guns as a result of three failed attacks. After the enemy surrounded the farm, Podust evacuated the defenders. For this battle he received the Order of the Red Banner.

The most effective crew was commanded by Lieutenant S.I. Kuleshov, who destroyed 2 Tigers and one PzIV. When the Germans attempted to get close, the tank crushed about 15 of them with its tracks, the rest ran off. His reward was the Order of the Patriotic War 2nd Class. Another Tiger was claimed by the SU-122 crew commanded by Guards Lieutenant V.F. Mikheev.

KV-85 in Crimea, 1452nd SPG Regiment, May 1944.

The end of 1943 and early 1944 was the peak of the KV-85's career. The small amount of tanks produced and heavy losses meant that these tanks were a big rarity by the summer of 1944. For instance, in the spring of 1944, 11 KV-85 tanks remained in the 1452nd SPG Regiment, which took part in the liberation of Crimea. Individual tanks were seen in various units in the summer and fall of 1944, but these were the last bursts of activity. Not a single mass production tank survives to this day, but the Object 239 is on display in Avtovo, St Petersburg. However, it was "improved" by welding on a bow MG before it was installed.


  1. Two questions:

    1) The articles I had read about the KV-85 said that "fillets" were necessary to install on the KV-1S chassis to fit the IS-1 turret, and I wasn't sure what a "fillet" was. Does this:

    "Bulges were added to the sides, and deflectors were added to protect the turret ring".

    Refer to that?

    2) Is this sentence:

    "The study of new tanks went at different rates. It was simplest for units that had already used the KV-85, as the difference between the two was slight."

    A misprint? Should it say "it was simplest for units that had already used the KV-1S"...?

    Also--as and afterthought---the KV-1S also sauntered on in service as late as 1945, I believe. I wonder if there was any consideration given to seeing if one could have fit T-34/85 turrets to KV-1S tanks, as a field modification. That was probably not worthwhile to do it with new T-34/85 turrets straight from the factory--these would be more useful on new T-34s---but using any T-34/85 turrets could have been cannibalized from T-34 tanks with irreparable chassis damage but the turret still functional? It would have made these old KV-1S tanks into something like ersatz "KV-85s" and increased their usefulness if it was possible.

    1. Oops, silly mistake, it would indeed be easy to master the KV-85 if you are already experienced with it ;)

      As for #1, yes, that is what I am referring to. Compare the sides of the hull to the KV-1S. There is a welded on bulge on each side to accommodate the larger turret ring.

      It was certainly possible to modernize older tanks like that, but as far as I know this was rarely done except by front line workshops that had no other choice. Considering that T-34s with 1941-1942 production low turrets remained in service throughout the war and even after it, a more radical modernization such as replacing a turret with a different tank's turret would have been unlikely.

      Interestingly enough, I've seen a model of what you are referring to, as Tamiya makes a T-34-85 and KV-1 in 1:16th scale, at least one person combined the turret of one and hull of the other to make a "KV-85", unaware that neither the hull nor turret were correct.

    2. Actually, what you refer to in the Tamiya model was exactly what I mis-learned decades ago. Back then tank books by respected authors showed pictures of IS-2 model 1943s and called them "IS-1s" and gave us mythical classifications such as T-34a, T-34b, and T-34c tanks. Those same books said that the KV-85 was a combination of a "KV-1b" (essentially the uparmored 1942 version of the KV-1) and a T-34/85 turret, and that they made no fewer than 4300 of them to boot!! They had many of the metrics wrong as well.

      The reason I made this suggestion is that despite the folklore of the books of that era, the Soviets were not callous towards the fate of their tankers and infantrymen--in fact, quite the contrary. The Soviets were both undergoing a manpower squeeze and moreover, were--in a friend's words--"fighting war increasingly like Western powers did, as a 'rich man's way of fighting'---poor countries are forced to 'burn bodies' while rich countries substitute 'burning' munitions and hardware to spare bodies, like the West". I would have thought there would be concern for risking tankers in an increasingly obsolete tank (in terms of firepower and armor) like the KV-1, and putting a T-34/85 turret improves both the tank's firepower and armor protection, which would save lives.

      To drive this point home, the same friend (whose house is a veritable library of military books) had a book on the Soviet order of battle that I can't seem to find on Amazon or anywhere, which noted in its preface how the Soviets were reacting to the manpower squeeze, disbanding units starting in 1944, to free up manpower for training and other purposes, and how things like how IS-2 crews had three times better a survival rate than T-34 crews.

  2. "the KV-1S 15002 hull. The alterations were not too great." Then why does the drawing of the lower hull of the KV-1S show the armor as 60mm and the drawing of a KV-85 lower hull show the armor as 75mm? BTW, a captured KV-85 lower hull was 60mm.

    1. 15002 was modified to build the Object 239 prototype, the production tank often incorporated further changes. That said, increased protection was not the goal of this project, so I don't know why it would be boosted to 75 mm. Perhaps it's one of those cases where someone made a mistake in their drawings and it propagated into other publications.