The More Turrets, the Merrier?

Right from the very beginning of the development of the tank concept, the idea that tanks could have multiple turrets to do multiple tasks at the same time was one that was very popular. Japan, Germany, the USA, and Poland all experimented with multi-turreted tanks, but none so much as the USSR and Great Britain. In the early 1930s, the UK produced the A1E1 Independent, Medium Mark III, Vickers 6 ton, and A.9 Cruiser multi-turreted tanks. The Soviet Union had produced the T-26 (a Vickers 6-ton copy), T-28 (based from the Medium Mark III), and the T-35A multi-turreted heavy tank, perhaps the most impressive multi-turreted vehicle to be manufactured in the Soviet Union.

The T-35A was, on paper, an impressive vehicle, but in reality, the vehicle was seriously flawed. It was too long, leading to major structural and mechanical problems, especially when turning, also being too tall and therefore dangerously overbalanced (during WWII, two T-35s would topple over due to the high center of gravity), and too many turrets which left the commander unable to adequately control the numerous crewmen and guns. It became clear that the T-35A was in desperate need of modernizing. T-35A chassis number 183-5 (the twenty-sixth T-35A manufactured) was taken to the testing grounds at Kubinka, near Moscow in 1936 and extensively trialed. After a year of these trials, it was decided that the T-35A was generally unfit for service. In the short term, the T-35A was moderately ‘updated’, but design bureaus were soon busily at work drawing up the Soviet Union’s new multi-turreted heavy tank.

Shaking up the Red Army

Dmitry Grigoryevich Pavlov was the Soviet commander in Spain during the Spanish Civil War during 1936 and 1937, and his experience fighting the Nationalist forces there had quickly seen him gain power within the Red Army. Eventually, in 1937, he found himself in charge of the ABTU (Armor and Automobile Management Bureau). Pavlov was very important in establishing the groundwork for a total overhaul of the Red Army’s tanks, some of which he had seen to perform poorly during the Spanish Civil War. While the main Soviet tank sent to Spain, the T-26, was highly regarded, it was often knocked out by light guns due to the thickness of its armor. The T-26’s armor plates were no thicker than 12 mm, almost no better than the tanks of World War One. This proved to be a major flaw with not only Soviet tanks but tanks all over the world.
In 1937, Resolution 94ss was passed. This was a general order from Pavlov for a total review of the entirety of Red Army stocks. Factory KhPZ 183 (Kharkov Locomotive and Tractor Works) was ordered to begin prototyping for a new multi-turreted heavy tank to replace the T-35A, and a new fast convertible tank to replace the BT-7. Despite this, KhPZ 183 found itself out of its depth developing two new tanks and was busily focusing on the BT tank replacements, the eventual A-20 and A-32, which led to the T-34.
Due to KhPZ 183’s inability to begin designing a new heavy tank, the project was partly handed over to Factory 185. After this, the Kirov Works was also invited to design a new multi-turreted heavy tank for the Red Army. On paper, three factories were now designing a multi-turreted heavy tank, these being KhPZ 183 (which had still technically had not pulled out of this race), Factory 185, and the Kirov Works.
By May 1939, Factory 185 had drawn up the T-100 heavy tank, and the Kirov Works had named their vehicle the SMK, after Sergey Mironovich Kirov, the short-lived chairmen of the CPSU (Communist Party of the Soviet Union) in 1934, who was assassinated not too long after. Much can be said on the death of Kirov, such as whether it was under the orders of Stalin himself, but nevertheless, after his death, Kirov became a much-celebrated figure in Soviet mythology. KhPZ 183’s project had not begun, and therefore at this stage, it became a two-horse race.

‘We are building a tank, not a department store!’

The SMK was originally designed with the T-35’s suspension, but this was deemed inadequate. Therefore, testing was conducted with a T-28 that had its suspension replaced by torsion bars. While not a total success, the potential was not lost on the engineers, and it was decided to implement this into the design.
There were now two tanks on the table, and both vehicles had a very similar internal layout. At first glance, the T-100 and SMK looked similar, but there were very different vehicles. The T-100 had coil spring suspension with rubber-tired road wheels, a different engine, turret shape and design, armor thickness, and even main armament in the shape of the L-10 76.2 mm gun.
Both the SMK and T-100 had three turrets. The SMK prototype originally had two small turrets, one forward and one behind a central pedestal. The main turret was perched upon this central pedestal. The smaller turrets had a 45 mm Model 1934 gun, capable of semi-automatic fire (the breach automatically locked when a shell was inserted, and the spent shell casing was automatically ejected once fired) when shooting armor-piercing projectiles, and quarter automatic fire (the breach automatically locked when a shell was inserted, but the spent shell casing had to be manually removed) when firing High Explosive projectiles. The main turret was equipped with an L-11 76.2 mm gun. The three guns were accompanied by coaxial 7.62 mm DT-29 machine guns, and the main turret had a rear ball mount that was given a 12.7 mm DShK machine gun.
The chassis of the original SMK prototype was octagonal, with a substantial overhang of the upper hull over the tracks and running gear, much like the earlier T-24 tank. The forward turret was placed off-center to the right, whereas the rear turret was off-center to the left, with a large armored radiator intake to the right of the rearmost turret.
The tank was powered by an 850 hp GAM-34T liquid-cooled diesel engine housed in the rear portion of the tank. The drive sprocket was also to the rear. The prototype, on paper, had eight road wheels and four return rollers.

Prototype drawings of the three turreted version of the SMK, with the top image featuring T-35 suspension, and the lower depicting torsion bar suspension. Interestingly, the torsion bar version still retains a track tensioning wheel between the idler and the first road wheel, something not seen on the prototype. Source: https://www.dieselpunks.org
On 9th December 1938, the two prototypes were presented to the ABTU, with wooden mock-ups of the two vehicles. Both prototypes were approved, but the design of both vehicles was requested to change, and the rearmost turret was to be removed from both tanks, reducing the turrets to two, one turret with a 76.2 mm weapon, and one with a 45 mm weapon. Some sources claim that Stalin himself requested this, and the mythology of the incident describes Stalin inspecting one of the two wooden mock-ups, and snapping off one of the sub turrets, exclaiming ‘We are trying to build a tank, not a department store!’ This is not verified anywhere and is highly apocryphal of Soviet doctrine at the time. As it was, the Kirov Works was well aware of the limitations of multi-turreted tanks and was already designing a single-turreted version of the SMK.

Prototypes

From this point, the prototype was approved for production. The tank was now to only have two turrets, instead of three, and due to the weight saved from this, the desired 70 mm thick glacis was able to be introduced into the design.
Now that the chassis was shorter, the prototype was given eight cast road wheels with internal shock absorbers and four rubber-rimmed return rollers. An adjustable front idler wheel was provided for the tank.
The frontal armor was 70 mm thick, and the sides and rear plates were 60 mm thick. The floor plate was 30 mm thick, and the hull and turret roofs were 20 mm thick. The hull no longer extended over the tracks, and therefore a fender was placed along the length of the chassis.

The SMK was an imposing tank, however, the design had some flaws, including a dangerously high and exposed turret ring, a flaw that was exploited during the combat trials in Finland. Source: TSAMO via Maxim Kolomiets
The hull was split into three compartments, not including the main turret. These were the forward fighting compartment, the central fighting compartment, and the engine/ transmission compartment. The crew consisted of seven men: driver, engineer/ radio operator, 45mm gunner, 45mm loader, main turret gunner, main turret loader, and, finally, a commander.
The main turret was given a P-40 anti-aircraft mount with a station for a DT-29 7.62 mm machine gun. The radio in the hull was a TK-71-3, standard in all Soviet heavy tanks. This radio had a rage of 15 km on the move, and 30 km when stopped.
The prototype entered the construction stage in spring 1939, but the design team at the Kirov Works was not happy with the outcome. Engineers knew that the tank was too heavy, limiting its combat capability. Due to the height and weight of the SMK, the vehicle was too cumbersome to be an effective fighting machine. Ultimately, the engineers knew that the multi-turreted tank concept was fundamentally flawed. Therefore, under their own initiative, they began working on a single-turreted version of the SMK.

A cutaway of the SMK prototype as produced. The turret displays features of the vehicle when it was deployed in Finland, the rear turret-mounted DsHK 12.7 mm gun has been replaced with a DT-29 7.62 mm machine gun. Source: vesna-info.ru

Kliment Voroshilov

The Kirov Works began to design a new single-turreted version of the SMK, and the tank they designed was similar to the SMK. Instead of two turrets, the smaller turret was removed from the design, and therefore there was no need for a turret pedestal. The turret ring was now flush with the hull roof plate. The new main turret was similar to that of the SMK, with an L-11 76.2 mm gun, but this prototype, named KV-U0, was given a coaxial 45 mm gun, so as not to reduce the firepower compared to the SMK. The engine of this prototype was a 500 hp V2 diesel that had been designed for the BT series. In this case, it was supercharged. The engine was also used in the T-34, known as the V-2-34, and the version used on the KV series was known as the V-2K. The V-2K was seriously strained when powering the KV-1, but it was completely overworked when powering the KV-2, with its much larger and heavier turret.
The new tank was named after Kliment Voroshilov, who at the time was a prominent figure in the Soviet Union, being one of the five Marshals of the Soviet Union. This new KV (Kliment Voroshilov) tank was submitted with the SMK for trials at Kubinka in the late summer of 1939.

Kubinka trials

The T-100, SMK, and KV tanks were all taken to the Kubinka training ground to conduct trials. The SMK had an advantage over the T-100, being three tonnes lighter than the T-100, and having better cross-country capabilities, but itself was at a disadvantage to the KV tank, the surprise entry for the new role.

Front view of the SMK. Notice the off-centered front 45 mm gun turret. This was to allow for an escape hatch for the driver on the hull roof. Notice the fabric on the front fenders hanging down almost to the tracks. This was likely some measure to curb debris being kicked up. Source: TSAMO via Maxim Kolomiets

The rear view of the SMK during Kubinka trials. The engine deck was very high from the ground, with a large air intake hidden under the upper portion of the hull. At the rear of the turret is a 12.7 mm DShK machine gun. During the combat trials in Finland in 1940, this gun was replaced with the standard 7.62 mm DT-29 machine gun. Source: TSAMO via Maxim Kolomiets
The trials did not go smoothly for either the SMK or the T-100. The SMK suffered from transmission failures during the trials, which were one of the major issues that were desired to be eliminated when replacing the T-35A. It did, however, perform marginally better than the T-100. The vehicle was able to ascend an escarpment of 37 degrees and travel at 35.5 km/h.
The tank that performed best during the trials was the KV. The weight and length saved by removing the secondary turret proved most advantageous. Additionally, the commander had a much easier time controlling the actions of the tank. The KV did not completely win over the crowd, however. The V2K engine (the name for the new V2 engine) was working at its absolute limit, and the vehicle had serious trouble crossing a moat.
This testing was done in early September 1939. This was too late for combat trials in Poland, but for the Soviet Union, another conflict was on the horizon that was a prime testing ground for the new vehicles.

The left side of the SMK at Kubinka trials. The swing arms for the road wheels can be clearly seen and was one of the major improvements over earlier Soviet heavy tank designs. The two turrets are conical in shape, with the main turret consisting of four main plates, and a pressed and shaped roof to maximize space inside. Source: TSAMO via Maxim Kolomiets

Combat Trials

The 20th Heavy Tank Brigade was deployed on the Karelian Isthmus, which was the most hotly contested portion of the Soviet-Finnish frontline. This piece of land was the primary concession requested by the Soviet government, as they felt that the Finnish border was too close to the strategic port and major industrial hub of Leningrad (nowadays Saint Petersburg). It was on the Karelian Isthmus that the strongest Finnish defenses were organized, which included the famous Mannerheim Line.
The Mannerheim Line was a cleverly designed series of limited fortifications that used the harsh terrain of the Isthmus to force Soviet forces to rely on the few poor roads throughout Karelia. Anti-tank and anti-personnel traps were interwoven with trenches, pillboxes, small forts, and even deep covered ditches to trap tanks trying to cross.
One of these concrete forts was known by the Soviets as ‘Giant’ and, on 17th December, the 91st Tank Battalion, along with other battalions of the 20th Tank Brigade, were committed to the attack.


The only known photographs of the SMK during operations in Finland are these stills from a Soviet propaganda film. The SMK is moving at speed towards the front. Notice that the tank is still 4BO green, but it has had snowfall accumulate on the nose of the tank. Source: Youtube.com
‘Giant’ was in a stony wooded sector of the front, quite unsuited to tank warfare, but the tanks committed themselves to the assault nonetheless. Contrary to standard practice, the KV was separated from the SMK and the T-100, and was assisting a company of T-28 tanks in the assault, following a tree line to the bunker. The T-100 and SMK were ordered to assist the infantry in crossing the stony open ground.
This attack did not go according to plan, and the T-100 and SMK were forced to call off the attack. Conflicting reports claim that the SMK did or did not get hit that first day. One account states that the vehicles were under intense machine-gun fire while supporting the attack, but remarkably did not suffer any hits. Finnish machine gunners were very well trained, and were likely concentrating their fire on the massed infantry accompanying the SMK.
Another combat report from AP Kunitsyn reads: ‘To test the fighting qualities of the new tanks, a rather difficult sector of the front was chosen. The front lines were between Summajärvi Lake and the non-freezing Sunasuo swamp. On the left of the height was an enemy camouflaged pillbox armed with 37-mm Bofors guns and machine guns. BOT (Armored Firing Points) covered two trenches, an anti-tank ditch and several rows of wire obstacles. Granite anti-tank racks stood in four rows. Together with the T-100 and KV tank, the SMK was to attack the enemy fortifications and capture the height at which the observation tower of the ‘Giant’ sat, which apparently served as a command and observation post. The actions of the three experimental tanks were observed by the commander of the North-West Front, commander of the 1st rank, S. K. Tymoshenko, commander of the Leningrad Military District, commander of the 2nd rank, K.A.
The hour of the attack arrived. A series of red rockets soared into the sky. The artillery preparatory bombardment was carried out in such a way as to not only suppress enemy defences, but also to break through passages in anti-tank barriers and minefields. With the last volleys of the artillery, the infantry went on the attack, and soon the tanks received orders to start moving forward. The commander of the SMK and the whole group, Senior Lieutenant Petin, buttoned down the hatch of the turret and, through an intercom, gave a command to the crew: “Forward!”

Fate and Cancelation

On 20th December 1939, special orders were given by Pavlov to remove the SMK, and recover it to the Soviet lines. Seven T-28 tanks, two 45 mm guns, and an infantry battalion were given the task of recovering the SMK. This, however, was not successful. One T-28 was knocked out by artillery fire near the SMK, 43 infantrymen were injured, and two killed. Therefore, the SMK sat in the snow. Soviet crews had left many hatches open to the elements, and snow and water got inside the tank, further damaging the vehicle.
The vehicle sat where it was lost until February 1940. The Finns had shown little interest in the behemoth, though the vehicle was photographed. The T-28 lost near the SMK was harvested for spares, as the Finns had captured a number of T-28s in working condition, and were in the midst of pressing them into Finnish service.
While this was happening, the ABTU was finishing up the job of choosing a successor to the T-35. This was given to the KV tank, which had proved the best of the three vehicles tested. The designers of the T-100, Factory 185, tried for a while longer to have their design accepted, but to no avail. A second KV prototype was ordered in December, and KV-U0 returned to Kirov to have a new, ‘big turret’ fitted to hold a direct fire 152 mm support weapon.
As for the SMK prototype, the vehicle was cut up and scrapped after February 1940. Interestingly, the crew who served in the SMK were very fond of the vehicle, and spoke warmly of its survivability.

The last photograph of the SMK known to have been taken by Finnish authorities. A T-28 can be seen in front of the SMK, one of the vehicles sent to help recover it. Source: Aviarmor.com
The SMK was a vehicle too late to be practical, as its replacement was essentially designed in tandem with it. The flaws in multi-turreted tanks had been adequately displayed. Despite this, the SMK was a fine vehicle, being heavily armed and armored. Strictly following the ABTU’s specifications for a new multi-turreted heavy tank, the SMK was the vehicle the Red Army was looking for, but not the one it actually needed. However, the single-turreted version of the SMK, the KV, became one of the most important and influential vehicles in the history of armored warfare.
Interestingly, despite the flaws in multi-turreted tanks, engineers at the Kirov Plant drew up plans for a future KV tank with multiple turrets. This was the KV-5, with a 107 mm gun in a main turret, and a small sub-turret equipped with a DT-29 machine gun. This vehicle never left the drawing stage.
While the SMK was scrapped, the T-100 was converted into a heavy assault gun and renamed the T-100Y. This vehicle has survived to the present day, and resides at Patriot Park in Moscow. The KV prototype, KV-U0, was deployed on the Western Front (from the Soviet perspective) when the German attack came on 22nd June 1941, and was captured intact by German forces. It was likely scrapped by the Germans.
The Finns took at least one official photograph of the SMK, and handed it over to their allies. One such ally was Germany, which was busy categorizing Soviet tanks (both before and during WWII). The Germans were well aware of the T-35A. German categorisation called the cylindrical-turreted tanks T-35A, the conical-turreted tanks T-35B (though the Soviet T-35B was an entirely different product) and, interestingly, they called the SMK the ‘T-35C’. Despite the tanks having little in common beyond having more than one turret, the Germans thought that there was enough of a similarity to call it a T-35.
The official name for all T-35s was T-35A. This includes conical-turreted tanks. The T-35B was a version of the T-35 with a V2 diesel engine, which was planned but not produced.

The right side view of the SMK. The chassis has eight road wheels and four return rollers. This would be cut down two six road wheels and three return rollers on the KV tank. This was ultimately more successful and less cumbersome than the SMK’s layout. Source: TSAMO via Maxim Kolomiets

Sources

Tanks of the Winter War – Maxim Kolomiets
T-35 Heavy Tank. Land Dreadnought of the Red Army – Maxim Kolomiets
Aviarmor.com