Monday 30 August 2021

Evolution and Revolution

March 29th, 1945, was an important date for Soviet tank building. The IS-3 tank, the result of a deep modernization of the IS-2 launched in April of 1944, was accepted into service on that day. The IS-3 had a complex fate. The army did not initially want to mass produce it, although the decision to do so later proved correct. The IS-3 was the last Soviet tank to be accepted into service during the Great Patriotic War. It did not reach the battlefield, but it worked flawlessly on the ideological front. The appearance of IS-3 tanks at the Victory Parade in Berlin was a true shock for the Western Allies, and this tank remained the gold standard for a modern fighting vehicle for seven years.

Two in one

The drama around the development of a modernization for the IS-2 tank rivals a soap opera. Initially the factory #100 design bureau was working on this project, but it was abandoned halfway through and the bureau began working on its own tank, the IS-6. The Chelyabinsk Kirov Factory SKB design bureau decided to work on their own modernization and even built a prototype. Nevertheless, the work started from scratch in the fall of 1944. The project was initially called "experimental prototype 701-A" and later "Kirovets-1". The lead designer on this project was N.L. Dukhov with M.F. Balzhi as the lead engineer. The project was meant as an intermediate step between the IS-2 and Object 701. The tank would use IS-2 components but receive radically improved protection designed using the experience of the Object 701, hence the index "701-A".

NKTP order #729ss issued on December 16th, 1944. This was the starting point for the development of an improved Kirovets-1.

The new tank took its first steps on November 25th, 1944. Experience from building the Object 701 was indeed used, especially when it came to the hull. The turret was different. It had a new squashed shape. The turret was developed by Balzhi himself. Legend has it that he got his inspiration from a soapbox. The tank was sent to the NIBT Proving Grounds in December of 1944 where it went through mobility and penetration trials. The tank passed 500 km trials but failed warranty trials due to the cooling fan breaking at 810 km. Testers noted that the production IS-2 was no more reliable. Penetration trials showed that the resilience of the armour increased radically. The front was immune to the 88 mm Pak 43 at any distance. The turret and hull had their weak points, but the commission gave a positive verdict overall. Interestingly enough, the commission report named the tank IS-3. This soon became the tank's main index. The factory gave it the blueprint index 703 and designation Object 703.

Cutaway drawing of the improved Kirovets-1. Only the first prototypes looked like this, the final production tanks were different.

ChKZ was not alone for long. Factory #100's specialists woke up in the fall of 1944. In parallel with the IS-6 they developed a modernized IS-2 tank called IS-2U. As with the IS-6 G.N. Moskvin was the lead designer and V.I. Tarotko was responsible for the hull. It was Tarotko who came up with the IS-2U's signature feature, the V-shaped upper front hull nicknamed "pike nose". This not only improved the tank's protection but allowed the driver's hatch to be moved to the top of his compartment. Correspondence referred to this solution as the "two-sloped nose".

The IS-2U was never built, but the design received acclaim from the GBTU and NKTP. Malyshev and Fedorenko sent a letter to Stalin on December 27th, 1944, informing him that they decided to unite the two projects. The front hull and commander's fire control features of the IS-2U were combined with the Kirovets-1. That resulted in a thoroughly modernized IS tank that was impenetrable to the German 88 mm Pak 43 at about the same mass. The same front plate design was planned for the IS-6. Interestingly enough, the IS-6 prototype was sent to Moscow in late 1944 where it became the Kirovets-1's direct competitor. Its appearance in Moscow didn't help. The results of trials with the disintegrating running gear and excessive mass compared to its competitor were already known.

The second improved prototype of the Kirovets-1 at the NIBT Proving Grounds, March 1945.

The letter to Stalin was merely stating a fact, rather than asking for permission. Malyshev signed NKTP order #729ss to begin development on December 16th. This order renamed "experimental prototype 701-A" to "Kirovets-1". The order required the Kirov factory to deliver 10 tanks with some radical improvements by January 25th. The requirements included complete immunity to the 88 mm Pak 43 of the front and upper sides at all ranges. The same was true for the front and sides of the turret. A mechanical gun rammer and fume extractor were listed among potential future improvements. Installation of the 122 mm D-30 gun would also be explored in the future.

These deadlines were unrealistic from the start. In addition to other work Kirov factory's SKB was occupied with, the list of desired improvements kept growing. The number of required changes rose to 20 by January 19th (although it decreased to 16 items later). This led to mayhem at the Kirov factory, as 52 groups of blueprints were finished and 34 were delivered to production by January 13th. This all led to delays at factory #200, which was delivering the hulls. By January 23rd it only completed one hull and began working on the second.

Factory #200 was expected to deliver five hulls and five turrets. The hulls were expected by January 15th and the turrets by January 18th. This proved impossible in practice as the last blueprints arrived on January 10-12th. As a result only one hull was delivered with two more being assembled, four turrets were cast but not delivered. ChKZ was also expected to send documentation for an improved turret. Blueprints for the improved hull arrived only on January 27th. UZTM also produced two hulls and two turrets. One hull arrived at ChKZ by the end of the month. The factory reported the receipt of three hulls by February 6th: one produced at ChKZ, one from factory #200, one from UZTM.

This tank had a factory #200 hull and UZTM turret.

Assembly of the first two Kirovets-1 prototypes began on February 3rd, 1945. These were only the chassis, as no turrets had arrived from factory #200. The hull was weighed before assembly. At 16,985 kg it was lighter than the IS-2 hulls from factory #200 (18,185 kg) and UZTM (17,851 kg). Assembly of a new tank with the UZTM hull began on February 6th, and the fourth one with a UZTM hull began assembly on February 9th. On February 9th two turrets arrived from UZTM. The Kirovets-1 turret weighed 7470 kg, the IS-2 turret weighed 6795 kg. 8 tanks and 4 turrets were in various stages of assembly by February 15th. The first prototype (serial number 2) with its brand new turret went on a test run on the following day.

The tank was lighter than the IS-2 due to a lighter hull and other changes.

Even though the initial tank served as the basis for the improved Kirovets-1, these tanks had many differences. Factory #100 and NII-48's experience played a big role, and not only when it came to improved protection of the hull. The new front plate reduced the tank's mass compared not only to the initial Kirovets-1, but also the IS-2, bringing it down to 45,870 kg. To compare, the initial Kirovets-1 prototype weighed 47,500 kg. The hull was 10 cm lower, but its length increased to 6900 mm due to the "pike nose". The thickness of the front plates was reduced to 110 mm, but their effectiveness remained the same. The upper sides were 90 mm thick, but sloped at almost 60 degrees. This was about equal to the resistance of the welded straightened upper hull of the IS-2 tank.

The thickness of the turret varied from 120 to 210 mm. Its shape was improved compared to the initial Kirovets-1. Like the initial tank, the new Kirovets-1 had a 520 hp V-11 engine. Fuel tanks in the fighting compartment were removed. The ammunition capacity was decreased to 28 rounds for the D-25 gun, but a DShKM AA machine gun was added. Since the shape of the IS-3's hatches was different than the IS-2's, the mount was installed on a special circular base that was shifted back during travel.

The tank's main feature, the "pike nose", was inherited from the IS-2U.

One of the significant advantages of the "pike nose" was the driver's hatch. It not only made it easier for the driver to enter the tank, but improved his visibility during travel. However, there were many complaints made regarding the driver's compartment at the first factory trials that took place on February 16th. The machine gun magazine and main gun ammunition racks to the left and right of the driver cramped his workspace. When driving in his upper position, the carrier for the observation device impeded his access to the gearbox lever. The hatch was small for use in winter clothing. There were also complaints about the seat. Testers also found issues with the fighting compartment and also found that the engine was hard to remove in field conditions.

The DShK machine gun mount can be seen from the back.

Tanks #1 and #3 were accepted by February 21st. Tank #2 went through a factory breaking in run and was sent to Moscow on February 20th. The tank was photographed first, but the photos were not good, so tank #3 was photographed instead. After driving for 40 km it went through some further improvements and was cleared for 1000 km trials.

The first stage of the trials showed that the oil radiator is not protected by anything. It was hit with foreign objects (small stones) and damaged three times. A protective mesh was introduced. Factory trials showed that the tank had an average movement speed of 31.5 kph on a cobblestone road. Various defects were discovered and the water temperature was near critical. The tank had to be repaired several times, and so tank #4 also went through the 1000 km circuit. This tank also had to be repaired. By March 19th tank #3 had travelled for 1026 km with an average speed of 26.3 kph on a dirt road. Trials continued until March 29th, by which point it had driven for 1922 km. A whole collection of defects was discovered that had to be corrected on existing tanks as well as future ones.

The engine deck was reworked to offer improved protection from air attack. Trials showed that this was still not enough and it was later changed.

The decision to urgently launch factory trials was timely. The NIBT Proving Grounds only received tank #2 on March 16th, even though it was sent on February 20th. As of March 19th it was still undergoing gunnery trials and had not started mobility trials. Those only began after March 20th. A top speed of 40 kph and average speed of 32.5 kph were obtained on March 23rd. On the next day the tank drove on a badly beaten dirt road with an average speed of 17.1 kph. 27 days were spent on trials in all, over which the tank drove for 1016 km (258 on a paved highway, 439 on a dirt road, 159 off-road, and 160 over the course of special trials), fired 110 rounds from its main gun and 910 rounds from the DShK AA machine gun.

Diagram of the armour of the second IS-3 prototype. The production tank was slightly different,

The trials showed that the average speed on a highway was 31.3 kph, 17.2 kph on a dirt road, and 16.6 kph off-road. Such a small difference between dirt roads and no roads was due to the roads' poor condition. This can also be seen in fuel economy trials. The tank burned 230 L per 100 km of highway driving, 390 L driving on dirt roads, and 460 L per 100 km off-road. The cruising range was also similar: 200, 120, and 100 km respectively. The engine temperature was high, a fact observed both during proving grounds and factory trials. The list of defects on tank #2 was similar to those discovered on tank #3. The difference was that tank #3 had already driven 1922 km by March 29th and the NIBT Proving Grounds only finished trials of their tank in April.

The tank during trials at the NIBT Proving Grounds. One of the main issues was overheating, a defect that ChKZ fought with until the middle of the summer of 1945.

The full range of gunnery trials was not performed at the factory, which is a part of the reason why the NIBT Proving Grounds began with shooting. The gun showed precision similar to calculations. The average rate of fire was 2-2.25 RPM. The location of ammunition was different from the IS-2. Since the turret had no bustle, the ammunition was located along its perimeter. The biggest problem was the location of some of the propellant casings next to the driver, which not only impeded him by making his workspace cramped, but were also hard to reach for the loader. Luckily, there were only a few of these inconvenient casings. Trials of the gun were quite successful, but the DShK was not so. Since there was no rest, precision was unsatisfactory. Several complaints were made about its mount which had to be corrected before the tank was put into production.

The third IS-3 prototype. This was the tank that went through factory trials, as a result of which the tank was accepted into service.

There were many complaints about the fighting compartment. The crew's seats were uncomfortable and the absence of a "classical" commander's cupola reduced visibility. There were issues with the observation devices in the turret, including the TSh-17 gun sight. The fighting compartment had a problem with fumes, as the ventilation fan could not deal with extraction fast enough at peak RPM. The commander's fire controls were deemed a good idea in theory, but executed poorly.

Vision diagram of the experimental IS-3 batch. Several changes were made as a result of its trials.

The armour protection was judged highly, but with a caveat. Preliminary tests of the turret showed that the quality of the casting was low, since cracks were found. The report frames this rather diplomatically, but in reality the turret cracked into pieces. Direct hits also caused the ammunition rack welds to crack. Cracking of the welding seams of the spaced side plates during mobility trials was also a warning bell, but it was not looked into at the time. The root cause was insufficient rigidity of the floor and sides of the tank. This later became one of the main defects during the tank's service.

An UZTM turret during trials. It turned out that the 70L steel was too brittle. Surface cracks found before the trials made the situation even worse.

A long list of desired improvements was composed: 15 items for the hull and turret, 10 for the armament, 15 for the fighting compartment, 4 for the driver's compartment, 5 for the engine, 9 for the cooling system, 10 for the transmission and running gear, 6 for the electric system and communications, and 4 for the tools stored in the tank. The tank was recommended for service after these issues were corrected. In practice, the decision had already been made weeks before the trials ended. A letter signed by Beria, Malyshev, Biryukov, and Korobkov was sent to Stalin on March 20th, 1945. The letter proposed accepting the "Marshal Stalin" heavy tank into service. On March 29th Stalin signed GKO decree #7950, accepting the tank into service as the IS-3. The decree required the delivery of 25 tanks in April, 100 in May, and 250 in June.

The only right choice

As strange as it sounds, the IS-3 could have not been accepted for service at all. Work on another tank, the Object 701, was going on in parallel. The GBTU considered this a higher priority project and a favourite for replacing the IS-2. The Armoured and Mechanized Forces Council of the Red Army wanted to petition Beria to accept the Object 701 into service in February of 1945, but Malyshev spoke out against the idea, saying that the tank needed more testing. Time was ticking, and the IS-3 was accepted into service while the trials were taking place. ChKZ also insisted on production of the Object 701, but Malyshev managed to defend the position of the IS-3 as the Red Army's next heavy tank.

The hulls and turrets were tested at the NIBT Proving Grounds in April of 1945. The hulls were produced at factory #200 and UZTM.

There was a number of reasons for this. The IS-3 partially reused components and assemblies from the IS-2, so putting it into production was not difficult. The Object 701 was a different story. Production had to be retooled, which meant that output would drop. All of the Kirovets-1's issues paled in comparison to those of the Object 701. Malyshev's intuition was proven right much later, when the IS-3 was removed from production. The People's Commissar of Tank Production clearly knew what he was talking about.

Result of firing the 122 mm D-25T gun at the front of the tank. As you can see, the front plate welds held.

The situation with IS-3 production by early April was far from ideal. Nearly all tanks produced at ChKZ were only accepted conditionally. They had to be improved, and the list of improvements was large. This situation did not prevent the subcontractors for preparing for large scale hull production. For instance UZTM cast 32 turrets and delivered 7 (out of an order of 24) in March of 1942. In April UZTM delivered 38 hulls and 25 turrets. Factory #200 delivered 25 sets of hulls and turrets in April. At the same time, warning bells were ringing. As mentioned above, a turret tested at the NIBT Proving Grounds on April 12-16th cracked after 29 hits. The armour the turret was cast from was deemed to be brittle.

The hull could be penetrated at an angle of 320 and 40 degrees at a range of 900 meters or closer. The driver's compartment roof was also a weak spot.

There was no delay in continuing the trials. From April 11th to May 8th, 1945, hulls from factory #200 and UZTM were tested. These trials are described from opposite sides in Soviet literature: some claim they were a complete success, others that they were an abject failure. There are some nuances to both evaluations. For one, hulls from two factories were tested with different results. Secondly, these hulls and turrets were produced to the same requirements as the first five hulls and turrets, but the required resistance was increased since then.

The upper side of a factory #200 tank after it was hit with an 88 mm shell. The side of the IS-3 tank was about as tough as the front of an IS-2.

The most important question that is often raised is the toughness of the front plate. The tank was shot at with 122 mm AP shells. The shells could not penetrate the front of the hull at 0 degrees at a range of 200 meters. One shot hit directly at the welding seam joining the two plates, which held up under fire. Penetration could be achieved at 40 and 320 degrees from a range of 900 meters or less. An 88 mm shell could penetrate the lower rear from 300 meters. The German shell could not penetrate the upper side even at 200 meters.

An UZTM hull after penetration trials. These photos gave rise to the myth about the bad front hull welds.

Where did the photos of a smashed up IS-3 hull come from? The answer is simple: this is an UZTM hull. The quality of welding on this hull in particular was judged to be unsatisfactory. A higher quality was required of UZTM. Nevertheless, the trials showed the most important thing: the front of the IS-3 could not be penetrated by the 88 mm Pak 43 at any distance, although the driver's hatch was a weak point. The NIBT Proving Grounds still noted that the IS-3's hull was weaker than the Object 701, hence the desire to accept the Object 701 into service.

May production IS-3 tank at the NIBT Proving Grounds. The first production IS-3 tanks looked like this.

The turret was worse off. It was cast from 70L steel like the IS-2, the problem was that it had a variable thickness which had an effect on its properties. Cracks were found in the UZTM turret even before the start of trials. Their results were mentioned above. The factory was barred from putting anything else into production without the involvement of NII-48. The institute was also ordered to urgently pick a new type of cast armour.

In summary, the reports that are so often discussed were based on the results of trials of test hulls and turrets. They were distinct from the hulls and turrets that went into mass production. The first tank that was meaningfully different from the first eight prototypes was assembled in March. The ninth tank had a new driver's hatch that was 60 mm wider, the mounting of the gearbox on its pedestal changed, the engine deck grilles were improved, a new engine compartment bulkhead was installed, etc. That wasn't all. The first production tank had a 30 mm thick driver's compartment roof, a radio in a new location, an improved loader's periscope and gun sight, new commander's hatch, protection for the turret ventilation fan, improved driver's workspace. More than 10 various improvements were made starting with the first production tank.

Mass production IS-3s were different from the prototypes from the very beginning. New changes were being introduced every month.

A new type of steel named 66LM was introduced as a result of joint work with NII-48. It was introduced at UZTM in May of 1945. All 109 turrets produced by the factory that month were made from the new steel. Improvements were also underway at factory #200. Special attention was paid to the quality of the welding. Factory #200 also noted cracks in the front of turrets in April of 1945. That month factory #200 introduced a new type of steel called 73L. 24 turrets out of 34 cast in April were made from this type of steel. A new finishing process was introduced on April 26th, which was applied to 11 turrets. 73L steel was not used for long. The NKTP decided that factory #200 will be producing turrets from 66LM steel on April 26th, 1945. As a result of stricter quality requirements, factory #200 delivered only 56 hulls out of 90 in May of 1945. As you can see, by May of 1945 the IS-3 already had a different hull and turret than those tested in April.

Engine deck of the production IS-3 tank. It was more resilient to attack from the air.

While subcontractors worked to increase quality of their products, ChKZ was rapidly preparing for production of the new tank. Improvements to the design were tested on tank #9 (serial number 703-67009). Overheating was one of the most pressing issues. The tank's top speed was limited to deal with this. The factory only began working on the April quota on April 20th, but even these tanks were only accepted conditionally. ChKZ reported that they were subjected to bench trials in the SB-2 workshop and only accepted in May of 1945. 35 defects were discovered during quality control of the first tank. At the same time, it was clear why Malyshev insisted on accepting the IS-3 and not the Object 701 into service. It would have taken several months to swap production over and the first prototypes would be even buggier. The IS-3s remained at the factory due to persistent cooling system troubles. Work on finding a way out of this situation continued in parallel. The experimental Object 704 was pulled into this work, as it turned out that while the IS-3 ran 15-20 degrees hotter than the IS-2, the Object 704 operated at the same temperature as the IS-2 and ISU-152. Work continued.

The IS-3 went through the biggest changes in July of 1945. 26 changes were made that month. They were introduced gradually, so the tanks changed throughout the month.

The new tank was more complex, and therefore more expensive. An IS-3 produced in Q2 of 1945 cost 310,000 rubles while an IS-2 cost 250,000 rubles. This high price was the least of the tank's problems. As traditional with ChKZ, delivery of May's tanks began towards the end of the month. Not a single one had been delivered by May 21st. The 100 unit quota for May was met on June 1st. Of these, one tank (serial number 703-18073) was sent to the NIBT Proving Grounds. The biggest delay was caused by the factory working on design issues. The cooling system remained the biggest problem. An improved design was due on June 10th.

The turret fan was also an issue. Various improvements were constantly being made, 7 items were completed in May alone. They included a new smokescreen belt rack, new ventilation fan, and a bar that made removing the upper fuel tanks easier. The full list of changes planned for the IS-3 was truly enormous: 177 items. June brought more issues. Only 140 tanks out of 250 were delivered by July 1st, with a promise to make up the difference by July 6th. There were many reasons for these delays, including breaking of fuel tanks on 75 tanks, issues with hulls, missing components (particularly turret races, water radiators, and front gearbox struts). Not a single tank submitted for factory trials passed them. There were positive notes: 207 tanks were shipped in June, and they were finally reaching their end users. A dozen more improvements were made to the design.

The cooling system issues were finally resolved in July. Thanks to changing the way the external fuel tanks were mounted it was finally possible to fully rotate the turret without having to remove them.

Work to resolve the issue with the cooling system continued. The solution was finally implemented on July 11th, 1945. The vehicles built in July had the most changes, some of which were not even described. These "hidden" changes include protruding upper front plates that acted as splash protection for the turret ring. The slope of the splash protection around the sides of the turret ring also changed. The driver's hatch lid received a bump stop. These changes were applied to tank 703-11500, which was tested at the NIBT Proving Grounds. In practice the list of changes made in July was longer. The configuration of the external fuel tanks also changed. Now the tank could turn its turret a full 360 degrees with them installed, although they still got in the way of the gun and would have to be removed in combat conditions. On July 20th, starting with tank 703-11530, the infantry buzzer plug was removed. Hardpoints for four spare tracks on the upper front plates were introduced on July 26th, starting with tank 703-11571. The saw was moved to the left side on July 28th. 26 changes were introduced in July in total. Some of these changes had a significant impact on the look of the tank.

Spare track links were carried on the front starting in July.

The aforementioned changes coincided with a production drama. Out of 250 tanks due in July only 181 were delivered by August 1st, with the promise of delivering the rest by August 4th. The reasons were the same: production defects and issues with subcontractors. There was another problem. Since the Great Patriotic War was over, workers and foremen began to leave ChKZ en masse and head to their pre-war occupations. This had a direct impact on production volumes. Issues with the V-11 engines overheating cropped up. The situation in August was the same. 195 tanks were delivered out of 250 with the promise of delivering the rest by September 5th. The quality of tanks continued to rise. 15 changes were made in August, including externally visible ones. For instance, a new convoy light was introduced starting with August 20th. Tools were moved to boxes along the sides. Handrails were added to the rear of the tank instead of lifting eyes.

Hardpoints for a heater were introduced soon after the spare tracks were.

A similar situation took place in September. The reduction of the quota from 250 to 230 tanks did not help much, as only 160 tanks were delivered by October 1st. The factory reported 12 changes in total, but at least a few were missed in the report. At the very least, the antenna port changed. It was installed at a tilt before September, and as of September it was straight. Three hatches were added to the V-11 engines to change injectors, thanks to which it was not necessary to remove the engine casing. The cost of the tank kept decreasing. In July-September of 1945 it cost 295,000 rubles.

The new antenna port was one of the changes introduced in September.

The end of the war meant that production volumes gradually decreased and factories were "demobilized" (for instance, UZTM). One must note that there was never much of a difference between UZTM and factory #200 turrets. UZTM turrets traditionally did not have casting numbers and the choke of the casting mold was different. UZTM stopped producing turrets in October. After 29 turrets in the backlog were used up, only factory #200 turrets were used to build IS-3 tanks. IS-2 turrets were built in parallel with IS-3 turrets in Chelyabinsk, as some of them had cracked and needed replacements. Production volumes gradually dropped. 200 units each were delivered in October and November. The situation with delays continued, as in reality by December 1st only 125 tanks had been delivered. Reinforced return rollers and a more rigid hull were introduced in December. 200 tanks were delivered that month as planned, plus 75 left over from November. In total 1705 IS-3 tanks were produced in 1945 (not counting the prototypes).

The V-11 engine changed. Three hatches for changing injectors were added sometime by September of 1945, thanks to which it was no longer necessary to remove the casing every time. A similar change was introduced for the V-2.

Production volumes drastically dropped in 1946. The quota was now 100 tanks per month. This was caused not only by the end of the war, but also organization of S-80 tractor production, which the bloodied USSR badly needed. The quota for February was raised to 120 tanks, which the factory managed. The factory delivered 130 tanks the following month, and this was the last increase in IS-3 production. The GBTU managed to push through the acceptance of the Object 701 tank into service. It was accepted into service with the Soviet Army under the index IS-4 on April 29th, 1946. This coincided with a radical drop in IS-3 production. 60 were delivered in April of 1946, 90 in May. 75 tanks were delivered in June out of 100, and even these were initially delivered with no turrets since they were late. Production was supposed to end in June, but 25 tanks were delivered in July due to delays. In total 2305 IS-3 tanks were built, 600 in 1946. The factory began to prepare for IS-4 production. Here one needs to refer to a quote from a ChKZ report covering the first five months of 1946. It speaks volumes about the situation.
"Preparations for producing the new IS-4 tank are going very slowly, as the factory is moving over to tractor production and the attention of factory management is focused on mastering and producing the tractors. Tanks are secondary in priority and little time is dedicated to them."
IS-3 tanks built in 1946 on a May 1st parade in Red Square.

It turned out that ChKZ did not manage to set up IS-4 production in 1946, and even in 1947 only 50 tanks were built. As for the IS-3, work on improving the tank stopped in 1946. The only big change was the addition of toolboxes behind the spaced sides of the tank.

Battle on the psychological front

One often hears claims that the IS-3 made it to the front lines for the Battle of Berlin with some German tank ace testimony offered as proof. These fantasies should be dialled back. There is no way the IS-3 could be used in the Great Patriotic War. Production vehicles were built only starting in late April and the prototypes would not be sent to the front lines, especially after the results of trials. The tank overheated and its turret was too brittle. The IS-3 shared the T-44's fate. 

The first IS-3s were issued in the summer of 1945.

The first IS-3s were issued to end users in June of 1945. The factory was still struggling with overheating (it was overcome only in July), and so the new tanks were only used for training. They could not achieve their top speed due to overheating. 100% battle ready tanks started arriving only in towards the end of the summer. This was the cost for such a rapid start of production of the IS-3. It's hard to blame the GBTU and NKTP. No one knew how long the war would last for and the IS-2's armour was not satisfactory. The IS-3 was reliable enough to survive one offensive operation, which was enough in wartime.

Tanks of the 2nd Guards Tank Army on parade in Berlin, September 7th, 1945. 52 of these tanks made an impression on the Western Allies.

Despite these growing pains, the tank was still chosen to carry the proverbial banner of Soviet tank forces at the Victory Parade on September 7th, 1945. For this purpose, units armed with the new tanks were transferred to Berlin. Tankers of the 2nd Guards Tank Army were chosen to take part in the parade. The IS-3s were in the back of the column, but not a single breakdown was observed. The tanks worked perfectly. These new heavy tanks were a real shock for the Western Allies. The IS-2 was already beyond anything they had to offer, and here there were new heavy tanks that looked like they arrived from the future. One can say that the IS-3 kicked off the Cold War. The IS-3 remained the golden standard of a modern tank for Western nations for 7 years. How could they know the drama that unfolded while the tank was going into production? The fact that production ended in 1946 and the IS-4 was produced instead also remained a secret.

Recalls took place starting in 1947, primarily due to the engine bed.

The IS-3 was in a curious situation. The tank routinely took part in parades, and not just in Moscow. However, many of them were sent not to army units, but to warehouses. This was one of the reasons why usage of the tank proved so difficult. The IS-2's use in battle generated lots of information that was collected by the GBTU, NKTP, and ChKZ. This information was used to make improvements to the design. Due to reduced usage of tanks the amount of information also dropped radically. ChKZ and the Ministry of Transport Machinebuilding that replaced the People's Commissariat of Tank Production in 1946 were left in the dark.

Recalls did not stop the IS-3 from remaining a constant participant in parades.

The alarm bells started ringing in 1947. The first issue was a defect in the engine bed. As of April 10th, 1947, 50 out of 315 tanks in the Soviet occupational forces in Germany had to have their engine bed reinforced. This was just the start. The recalls grew and so did requirements for refurbishment. The question of modernization was raised by 1948. This modernization began taking place in 1951, but this is a whole different story. One can only add that the IS-3 never fought in its initial form. The tanks that were sent to Budapest in 1956 already went through the UKN (resolution of design defects) program. Nevertheless, three tanks survived in their original form: two of them in Poland and one in the Czech Republic.


  1. I just chanced by this article in Forbes, by David Axe. Enjoy!!

    Though I think the article got one thing wrong, the 90-mm Israeli rounds also failed against the frontal armor of the IS-3.


    In June 2014, in the early weeks of the war between Russia and Ukraine, separatists in eastern Ukraine were desperate for heavy weaponry.
    Rebels in Kostiantynivka, a city in Donetsk Oblast, eyed a 68-year-old Soviet-made IS-3 heavy tank resting atop a concrete slab. The tank was part of a monument commemorating the liberation of Kostiantynivka from
    German occupiers in 1943.

    They popped open the hood, tinkered with the engine, fueled up the thing and turned the ignition. Incredibly, the 51-ton vehicle actually worked. What’s more, it apparently worked in combat. “Good Soviet engineering is still able to serve today, and will serve in fight against [the] Kiev junta,” a separatist videographer crowed.

    To be clear, the Donetsk IS-3’s 122-millimeter cannon didn’t work. But the tank still could move, its 200-millimeter-thick armor still could deflect enemy fire and it still could mount machine guns.

    That the IS-3 functioned at all after more than six decades prompted
    James Warford, a retired U.S. Army major and former tanker, to celebrate the IS-3’s design. “Performance assessments of the tank incorrectly judged it as a failure,” Warford wrote in the winter 2019 edition of Armor, the U.S. Army’s official tank magazine.

    In combat, the results were unspectacular. Soviet IS-3s took part in the 1956 invasion of Hungary. Local forces lobbing Molotov cocktails managed to destroy several of the tanks.

    Those few losses tarnished the IS-3’s reputation. “For many observers, the dramatic photos of destroyed IS-3s, including a well-known photo published in Life magazine showing a number of coffins in the street alongside a destroyed IS-3 after a battle, provide all the information needed,” Warford wrote.

    In the eyes of critics, the IS-3 fared no better in its next war.

    The Soviet Union provided scores of IS-3s to Egypt. During the 1967 Six-Day War, the lumbering Egyptian tanks rolled into battle against Israel’s nimbler M-48s. In fighting around Rafah, the Israeli tanks destroyed several IS-3s with 90-millimeter cannon fire. Inexperienced Egyptian crews abandoned some other IS-3s.

    The ‘67 debacle worsened the IS-3’s reputation. But that’s unfair, according to Warford. After all, the IS-3s at Rafah destroyed several M-48s. And it’s not the fault of the tanks that some frightened crews abandoned them at the first sound of gunfire.

    “This desperate action had nothing to do with the capabilities of their tanks,” Warford wrote. “It was in fact all about poor training, low skill-level and lack of motivation in those Egyptian tank units.”

    After the war, the Israelis tested their own weaponry on some of the IS-3s they captured. “During this testing, captured Egyptian IS-3Ms were repeatedly fired on and hit by 105-millimeter armor-piercing discarding sabot ammunition without the tank’s frontal armor being penetrated,” Warford wrote.

    The tests underscored the basic soundness of the IS-3 design. So what if the IS-3’s purported failure actually was the result of bad press and panicky crews? It’s important to accurately assess the enemy’s technology—and project how well it might work in the hands of skilled and confident operators, Warford stressed.

    “Eliminating confusion like that surrounding the IS-3 must be a priority in today’s military environment,” he wrote. “As the world situation changes and continues to remind us of the Cold War years, success on the battlefield may depend on getting it right.”

    As for the Donetsk IS-3, it fought only briefly on June 30, 2014, Warford explained. The Ukrainian army captured the tank intact, demilitarized it and put it on display near the National Military History Museum in Kiev.

    1. Not only did 90mm rounds fail, there are photos showing some test firings the israelis did that showed the frontal armor largely resisting the early type 105mm APDS.

      105mm APDS testing - only one actual success.