Super-heavy tank (1941-1942) – 3 prototypes
The best known fake tank
The KV-VI, or KV-VI Behemoth, is one of the most famous fake tanks on the internet. A super-heavy tank project armed to ludicrous proportions, with three prototypes claimed to have been built 1941-1942, serving against the Germans near Moscow and Leningrad. This was not a hoax as many will claim, but in fact a fantasy model which was entered in a sci-fi scale model competition that has been taken out of context since it was posted on the internet back in 1997 by its creator.
The vehicle originated as a model built by Brian Fowler in 1995 by using parts from two Tamiya KV-2 kits, two Tamiya KV-1E kits, an AER T-38, an Italeri BT-5, an Italeri Katyusha, a Zvezda T-60, and Dragon tracks. Three KV hulls were cut and welded together with epoxy glue, the central dual-KV-2 turret’s pedestal was made using a shaving cream lid, and most of the details such as the DTs, ladders, and flamethrowers were carefully scratch built.
Photos of the KV-VI model were posted on the Track-Link website in 1997, alongside a fake history, some specifications and a set of reference books (none of which actually exist and are spoofs of real books – EG. “Dreadful Din on the Eastern Front” is a spoof of “All Quiet on the Western Front“, and “The Behemoths are Burning” is a spoof of “The Tigers are Burning“). The original page can be seen on their website.
In recent years, the KV-VI’s popularity can largely be attributed to the cutaway illustration by VonBrrr on Deviantart in 2010, which is used very often when discussing the KV-VI. Similarly, with the proliferation of easy-to-use photoshop technology, some historical-looking photos also appear often, supposedly of the KV-VI. These photos and the originals can be found in the gallery present on this article. Some other illustrations and photoshopped images often float around the internet, and it is likely that more will appear in the future.
Brian Fowler’s original model, as it appeared on Track-Link. Despite this being the original, there are many variations on the design from all the other illustrations of the type in the way the armament is arranged.
The fake history
Since the collapse of the Soviet Union, new facts have surfaced about the secret weapons developed by the Red Army during WWII. One of the most fascinating of these was the KV-VI Behemoth. In July 1941, Stalin learned of a single KV-II that had held off the entire 6th Panzer Division for more than a day [at the Battle of Raseiniai on 24th June]. With the incredible success of this single tank, Stalin ordered a crash [quick] program for a land battleship based on the KV-II design. It was to have three turrets and be very heavily armed and armored and able to defend itself against all types of attack. The project was given to the joint team of Kotin/Barykov. When the designers complained to Stalin that the insistence on three turrets made the vehicle too long to have an acceptable turning radius, Stalin’s answer was: “It doesn’t need to turn, it will drive straight to Berlin.”
The final design became known as the KV-VI “Behemoth”. The KV-VI was a multi-turreted tank using components of the KV-I and II, BT-5, T-60, and T-38. The use of existing tank designs was necessary because of pressure from Stalin and the strains put on Soviet industry by the German invasion. Because of its massive weight, the tank was equipped with wading devices permitting it to traverse rivers up to 9 feet deep. The team also designed a removable observation tower that could be used to direct the fire of the howitzers and rockets while the tank was in a turret down position.
The first prototype was completed in December 1941 and was rushed into the defense of Moscow. In its first action during a dense winter fog, the rear turret accidentally fired into the center turret. The resulting explosion completely destroyed the vehicle. The second prototype was completed in January 1942, and was sent to the Leningrad front. This one had indicators installed to show when another turret was in the line of fire. In its initial attack on the Germans, the tank broke in half when crossing a ravine. A spark ignited the leaking flamethrower fuel and the resulting explosion completely destroyed the vehicle.
The third prototype had a reinforced hull and was also sent to the Leningrad front in early 1942. It did manage to shoot down three German aircraft. In its first ground engagement, the KV-VI was firing on German positions when coincidentally all of the guns fired from the 3 O’clock position a the same time. The tremendous recoil tipped the tank into a ditch and the severe jostling set off the 152mm ammunition, which completely destroyed the vehicle. After these failures, Stalin cancelled the project, and many of the design team members spent the rest of their lives in the Gulags of Siberia. The KV-VI was nicknamed “Stalin’s Orchestra” by the few Germans that encountered it because of the variety of weapons it deployed.
Brian Fowler’s Legacy
Since the release of this article, there has been an email correspondence with the original creator of the KV-VI article, Brian Fowler. He has kindly provided some additional photos of the original model, and a personal insight on the legacy of the KV-VI. He has made many prize winning models (both national and regional), but none have gained the sheer fame (or infamy) of the KV-VI. He said that the KV-VI was built as a bit of fun after building some very accurate and detailed models that required substantial research, and was entered in a sci-fi scale model competition – it won the following awards: “Best Sci-Fi IPMS Buffcon Show, 1996“, “1st place, Hypothetical, Noreastcon, 1997“, “1st place IPMS National Show, Columbus, 1997“, and many more awards from regional shows. In fact, it was so popular, it even made it onto the April Fools cover of Boresight in 2008. The KV-VI even attracted the attention of Steven Zaloga, who said “Your tank is famous with Russian modellers… They don’t know you, but they know your tank.”
The KV-VI was not an intentional hoax, and he had hoped that the fake books would tip off the readers that it was a fake tank, what with them being spoofs of real books, but “unfortunately my humor is a little too subtle for some“. Furthermore, Fowler said “The KV-VI was the most fun I ever had building a model, as it allowed me to be much more creative and imaginative, coming up with a cool looking design and not having to correct kit errors or 100% accurizing.” With regards to the spreading of the KV-VI on the internet, he said “It gives me personal satisfaction that many around the world enjoy it for what it is, and I regret what has happened on the internet that leads many to be fooled or believe it was a hoax.”
Probably the most famous photoshopped image purported to show a KV-VI prototype during a parade in the Red Square. Besides the fact it looks quite different from other illustrations of the type, it is actually just several T-28s on parade photoshopped to look as one vehicle. The original photo can be seen on the right.
KV-VI by Sir-Zora-Crescent, 2013, taken from deviantart. Despite being clearly fake, this image at least appears faithful to the original model.
Perhaps the most famous cut-away illustration of the KV-VI made by VonBrrrr. The design varies from the original in having an extra BT-5 turret, having the T-60 turret armed with 2 x 20 mm (0.79 in) guns instead of machine-guns and replacing the center T-38 turrets with a single T-70 one.
Photos of Brian Fowler’s original KV-VI model. Courtesy of Brian Fowler.
Previously unseen photos of the KV-VI model before painting. It shows that there was an observation tower for the dual KV-2 turret, and these components are stowed on the hull.
The KV-VI as it stands now, in a display cabinet. Below is a DML T-35, which it dwarfs!
KV-VI supposed specifications
|Dimensions (L-W-H)||15.6 x 3.3 x 4.65 m (51ft 4in x 10ft 10in x 15ft 3in)|
|Total weight, battle ready||138 tons (276,000 lbs)|
|Armament||2 x 152 mm (6 in) L20 howitzers|
2 x 76.2 mm (3 in) L32 guns
1 x 45 mm (1.77 in) Model 37 gun
2 x 12.7 mm (0.5 in) DShK machine-guns
2 x 7.62 mm (0.3 in) Maxim machine-guns
14 x 7.62 mm (0.3 in) DT machine-guns
16 x BM-13 rocket launchers
2 x Model 1933 flamethrowers
|Armor||7 to 160 mm (0.28 – 6.3 in)|
|Propulsion||3 X V-2 engines(600 hp)|
|Speed||21 km/h (13 mph)|
|Range on/off-road||160/70 km (98/43 mi)|
An email correspondence with Brian Fowler, creator of the KV-VI
“KV-1 and KV-2 Heavy Tanks” by Steven Zaloga
“Armored Champion: The Top Tanks of World War II” by Steven Zaloga
“Soviet Tanks and Combat Vehicles of World War Two” by Steven Zaloga and James Grandsen
“World War II album, volume 9: Soviet heavy tanks” by Ray Merriam
“Russian Tanks of World War II, Stalin’s Armoured Might” by Tim Bean and Will Fowler
Fair commentary from the Tanks Encyclopedia Staff was also used in the writing of the “Reality” section of this article.
Superheavy projects have never worked
A short history lesson in Soviet tank designing is needed to explain the absurdity of the KV-VI. The idea of a land battleship is not something uncommon with interwar Soviet tank projects, but almost all of them had been abandoned before WWII began, such as the Tank Grotte, T-35, SMK, and T-100. Even more conventional superheavy tank projects (if such words can be used in the same sentence) designed during the war like the KV-3, -4, and -5 never left the drawing board, although this was for a variety of reasons, including the problems with weight, cancellation of the 107mm gun project, and fall from favor of heavy tanks. Heavy and superheavy tanks had proven too expensive, inefficient, with their low mobility and huge structural problems due to their sheer weight. In fact, the only real success from any of these heavy and superheavy projects comes from the SMK, which was redesigned into the KV-1 in 1939.
In the history, it is suggested that the team was headed by Kotin and Barykov. Barykov was part of the experimental OKMO design bureau since 1930, and handled projects such as the T-41 superheavy tank, T-35, T-29 (experimental upgrade of the T-28), the T-111 breakout tank, and the T-100 superheavy tank, as well as other more conventional projects such as the T-26 and T-50. The OKMO design bureau was broken up during the Great Purge by the start of WW2, and Barykov’s name does not appear on any further projects.
Kotin, on the other hand was busy with other projects during the time in question. These include, but are not limited to: the T-60/70/80 series, the real KV series, and the IS series – he would never have time to supervise such a large project. It is true that Kotin had a history of working with multi-turreted tanks, as some of his first work focused on improving the T-28, and he oversaw the design team of the SMK prototype, but this is not the full story. Even before the war, Kotin was apprehensive about tanks with more than two turrets, but Stalin was not. Stalin was heavily involved in military affairs even in 1938, and tank designs were often presented to him and a committee of his advisers. According to Tim Bean and Will Fowler’s “Soviet Tanks of World War Two, Stalin’s Armoured Might” (which lacks proper source citation, and therefore may be untrue), when the SMK and T-100 wooden models were presented at a meeting of the State Defense Council on 4th May, 1938, Kotin argued against having three turrets, because he knew that it severely undermined the mobility of both prototypes. Stalin agreed, and reportedly responded by ripping a turret off of one of the models whilst shouting “Why make a tank into a department store?!”
Joseph Kotin, who was said to be the leader of the KV-VI project, was a real tank designer, and perhaps the USSR’s most successful and prolific.
Frequently enough, Stalin seems to have been willing to listen to his engineers and field commanders on matters such as this, so the suggestion that he would overrule his engineers, as mentioned in the fake history, is unlikely. Once both SMK and T-100 vehicles had been modified to have two turrets, prototypes were produced and were sent out for testing at Kubinka in May 1939. Kotin and his assistant, A. Yermolayev were now beginning to think that having two turrets was still too many. They remarked that the crew compartment was cramped, and there were still weight problems. Acting without any higher approval, Kotin set his team to work on a single-turreted SMK which would become known as the KV-1.
The SMK tank is covered in snow, having been knocked out by an AT mine in August, 1939. It was not recovered for two months as a result of its weight. A T-100 prototype tried to tow it away, but to no avail.
Once the plans for the KV-1 were presented to Stalin, they were approved for trials alongside the SMK and two T-100 prototypes in the Winter War. It was there that the SMK was destroyed by a landmine, and the T-100s proved ineffective as a result of poor mobility, although one was later converted into the SU-100Y. It was the KV-1 prototype which excelled (except for the problems faced against heavy bunkers at the Mannerheim Line, thus leading to the creation of the KV-2). This success of a conventional heavy tank was effectively the end of the line for any multi-turreted tank designs; it is clear that Kotin would never allow such a project to take off.
The T-100 tank. It was a similar design to the SMK, but nevertheless, its construction was different. Both were considered too bulky and unreliable to warrant production, and they were less than half the weight of the purported 138 tons of the KV-VI!
Loss of faith in heavy tanks in 1942
However, heavy tanks were not necessarily favored by Stalin after the early stages of the war, due to reports of their effectiveness, or lack of. It is true that at the very beginning of the war, the KV-1 was the most formidable tank that the Red Army fielded, but this quickly changed by 1942 as a result of the Germans upgunning their Panzer IIIs and IVs in order to deal with this threat. The report of the KV tank at Raseiniai as mentioned in the story is true, but Stalin was also hearing scathing reports from Soviet generals such as Pavel Rotmistrov of their overall performances as a result of their mobility and outdated gun.
The Red Army needed mobility to chase down retreating panzerdivisions and close gaps in broken Soviet defenses as quickly as possible, something which the T-34 gave. The T-34/76 was arguably a superior vehicle to the KV-1, at least for the purposes of the Red Army, as it featured the same gun, but it was much more mobile, it was cheaper to produce, and the lack of armor was compensated for by the numbers in which the T-34 could be fielded in – simply put, what it lacked in armor, it gained in mobility and cost-effectiveness.
Having said this, not all generals agreed with Rotmistrov, and there was a real division in Soviet leadership over heavy tanks. Many saw the KV-1 as one of the greatest assets to the Red Army at the time, because it could be used to break through enemy lines, and defend against some of the heavier German attacks, relatively unscathed. In fact, the KV-1, in theory, had a much longer ‘life expectancy’ than a T-34 because of its superior armor, but on the other hand it could not always perform the same crucial roles. So, even despite the KV-1’s qualities over the T-34, it was clear that the T-34 was rapidly gaining favor with Soviet leadership, so in order to keep heavy tanks in production, a compromise was needed – a compromise that was an absolute disaster.
Enter the KV-1S – an attempt at trying to balance the armor of a heavy tank, and the speed of a medium tank. Unsurprisingly, this ambitious project could hardly do either, leading to its cancellation in late 1943, just a year after production started! It was as expensive as the KV-1, but gave combat results no better than the T-34 due to its similar armor, but still inferior speed.
The success of the KV-1 and the T-34 were based on their respective extreme qualities (speed for the T-34, and armor for the KV-1). The medium and heavy tank classes were very different things – any balance between these two extremes would not, and did not, give the desired effect.
By 1943, at least 43 heavy tank designs and proposals were rejected, even though the majority seemed conventional and sound designs, thus showing the lack of faith that most in the Soviet leadership had in heavy tanks. Also remember that many of these projects would feature the then-experimental 107mm gun – a project developed at Leningrad which was canceled, due to fears of Germany capturing Leningrad.
This was not the end of the heavy tank, of course. Thanks to lobbying from the NKTP (People’s Commissariat of the Tank Industry of the USSR), and as well as the need to combat new German heavy and medium tanks, heavy tank production was finally saved by the introduction of the IS series, and the KV-85 stopgap – modern, well-designed, and from a time when the USSR was on firmer footing in the war.
Based on this information, it is clear that if the KV-VI project were to exist, nobody would support it. Top engineers (such as Ginzburg, Kotin, Yermolayev, etc) would see it as near technically impossible and exceptionally unreliable. Generals and commanders would probably just consider it a bunker moving at a snail’s pace, which would be of little use to the Red Army, as it would not be able to fall back to defensive positions, or be moved into a new position with ease – the Germans could simply flank the vehicle as a result of their refined armored warfare tactics, owing a lot to their prolific use of radio. Above all, it would take so long to complete and it would cost so many resources that it would wipe out Soviet tank production, probably meaning that the Wehrmacht would be able to break Soviet defenses before the vehicle would be complete.
Lack of resources
One key problem of making a wartime project of this scale is that the USSR needed tanks in vast quantities. This is for three reasons. Firstly, the sheer size of the Eastern front required the USSR to field vast numbers of AFVs to simply keep the land covered! Secondly, during late 1941 and early 1942 the Soviets were desperate to get as many armored vehicles to the front as possible in order to replace the rapid losses incurred by the Germans – the sheer need for AFVs meant that even semi-armored vehicles and tractors were being converted in order to supply more tanks to the troops. This improvisation was not just comprised of field conversions, but it was done through serial production with three different vehicles – the Odessa Tank (Na Ispug), KhTZ-16, and ZiS-30 – needless to say, this is a hallmark of a desperate industry. Thirdly, during the period in question, most tank factories were being relocated to the safety of the Urals, which seriously disrupted Soviet industry, and would mean that a huge project like this would be disrupted beyond completion due to logistics alone.
In these conditions, it is extremely unlikely that even with all the support from generals, engineers, and politicians, the Soviets simply could not have wasted time, resources, and skilled workers on developing even one such vehicle, let alone three. In fact, even if Soviet factories were not disrupted by relocation, they may not have even been well-equipped enough for such a project – there was a huge lack of resources, especially in Leningrad, which was under siege, so much so, that they had to cancel a highly promising, and conventional armored car design that was due to enter mass production, the BA-11.
More costs and problems are prevalent when the logistics of creating such a vehicle are considered. Turrets and guns would have to be delivered from many different factories. These include, but are not limited to: the BT-5 parts coming from Kharkov Komintern Locomotive Plant, the Katyusha rocket launchers from Voronezh Komintern Plant, the KV parts from Leningrad Kirov Plant or Chelyabinsk Tractor Plant (after 1941), and the T-60 parts from GAZ in Moscow, or Leningrad Kirov Plant.
Based on this information alone, a wartime superheavy project of such proportions would be a sheer impossibility.
The design makes no sense
Coming back to the design of the KV-VI, the most ludicrous feature is the armament. With no less than 5 guns, 16 rocket launcher rails, 2 flame-throwers, and 18 machine-guns. The twin 152 mm (6 in) gun turret is especially dubious. The original KV-2 turret could only be traversed on relatively level ground, and it also posed stability problems as it was, while the KV-VI is supposed to have two of those guns, which are also pictured to be independently aimed. This is why 152mm guns were never used on turreted Soviet tanks again, for example, the late war SU-152, and ISU-152 used casemate 152mm guns, because they made the vehicle more structurally sound.
Even the flamethrowers are a peculiar weapon to put on the KV-VI, as these close ranged weapons which would have been very hard to use given the limited mobility of the vehicle.
The idea of mounting a turret on another turret is rather impractical. This arrangement would have made it necessary to mount a traverse engine on top of the first turret, thus making the tank top heavy and cramped further, or traverse the upper turret by hand, which was very slow. Secondly, any movement of the lower turret would have impaired the aiming of the upper turret, which throws the practicality into question. Thirdly, if the upper turret were to fire, it would have greatly stressed the turret mounting of the lower one and could alter the shape, if not eventually break the turret ring. Finally, in order to fix any of the aforementioned problems, it would take years, if not decades of precise engineering with a vast budget and expansive team of engineers that would never have been available to the USSR during the war or even before.
A big problem with the placement of turrets and weapons is the location of the BM-13 rocket systems. The sketch from DeviantArt shows it to be placed on top of a BT-5 turret, which is placed on top of a giant KV-1 turret (although in the original model, it is just placed on top of a single KV-1 turret). It would be difficult to reload the rocket system as it is placed much higher than on other vehicles such as a ZiS truck or a turretless T-60 tank. According to the model, a large piston controls the elevation of the BM-13 systems which is connected to the KV-1 turret. This is simply not possible, as there would be little space in which to mount such a large piston inside the lower KV-1 turret, especially as space is needed for the crew members, gun, and ammunition. There also appears to be no space for storing rockets, except for on the exterior of the tank where on the model, a wooden crate can be seen. This is a practice sometimes done by tanks that have little space for ammunition, such as an ISU-152, but this was rather dangerous, as the munitions could be hit and could, at best, unusable, or at worst, detonate.
The DT machine guns are also placed in unorthodox places – the sides of turrets. This is only seen on very early Soviet tanks, such as the T-12 and T-24, as well as armored trains. The usefulness of fixed DT machine guns is dubious even on conventional tanks (which is why they were not featured on post-war tanks), and it is unlikely that they would be able to effectively engage and track a moving target, as the turret would traverse too slowly. Apart from which, these would be an unnecessary weak point which would also cramp the already overloaded turrets.
What looks like some kind of KV-VI is just an MBV-2 armored train at the Leningrad front. The USSR had many built before the war (as a result of successful use during the Russian Civil War), but many were lost in 1941. This is an early train, as the later ones featured T-34/76 and KV-1 turrets.
The KV-VI was purportedly powered by 2 or 3 KV-1 engines with 500 hp each, and that would have given a power-to-weight ratio of 11 hp/ton. While that is not exactly abysmal, the sheer track length and narrowness of the vehicle would have made turning the KV-VI similar to the way a train turns. Traversing, that is turning on the spot, would have been highly improbable if not downright impossible. The 2 or 3 such engines would have also taken a lot of space, and it is not clear where they would have been mounted. Based on the model, an engine was present behind each turret, but getting their power to the rear drive wheels would have required a transmission which is probably not feasible even today.
There were few, if any, bridges at the time which would have been able to sustain the 138 tons of the KV-VI. Crossing any kind of hill or ravine would have over-stressed the chassis to the point where it was very likely to break in two, which would have also made river wading impossible – despite the fake history suggesting that wading devices were fitted. Also, the ground pressure was abysmal, meaning any attempt to cross a river would have left the tank stuck in the mud almost instantly.
Another peculiarity is the fact that the number of weapons greatly outnumbered the number of crewmen, which stood at just 16, including the driver and a commissar. They had to aim, load, and fire 5 guns, 18 machine-guns and 2 flamethrowers mounted in 7 turrets. Having a crew which could fully man every gun would perhaps number as many as thirty men. This would be impossible to control by one single commander, and the vehicle would have to work more like a naval battle ship, meaning that a commissar (who acts as a ‘supreme commander’) would have to give general orders (such as which direction or when to commence fire), and each section would need a dedicated commander in order to control which guns fire where. This would require multiple radios or intercoms, and it is imperative that all of these advanced electronics are maintained in perfect working order, or the vehicle could face a disaster.
Lack of sources and other holes in the story
A more fundamental concern with this vehicle is the fact that there have been no purported reports from the Wehrmacht about this vehicle. If there were three prototypes sent to Moscow and Leningrad, it would be incredibly conspicuous. Explanations could be made up for why this is so, such as considering that the Germans knew about the SMK prototype in Finland, but they wrongly called it the T-35C, this might suggest that German intelligence was far from perfect, and could lead to an overlooking of the KV-VI (and even this suggestion is incredibly ropy). However, this is a different situation all-together – the KV-VI would dwarf the SMK, and Germans themselves were reported to have faced off against three prototypes at Moscow and Leningrad, some of the busiest fronts of the entire war. This should have cast immediate doubt on the KV-VI as a real tank before even considering how unbelievable the vehicle itself is.
A final and fundamental mistake is the way the name is spelled. No Soviet tanks, from the early T-18 (1928) to today’s T-14 (2015), have had Roman numerals in their designations. With regards to the real KV-6, it is speculated that there are at least two candidates for the KV-6 name, one being a KV-1 with a flame-thrower installed in the hull (according to Henk of Holland), while the other is a version of the KV-7 self-propelled gun (the KV-6 featured a 76mm and twin 45mm guns, whereas the KV-7 had twin 76mm guns) according to Steven Zaloga in “Soviet Tanks and Combat Vehicles of World War Two“. However, the KV-6 index seems to be unknown, and any documentation may have gone missing during the war.
Could the KV-VI work?
It is difficult to entertain the practicality of the KV-VI, but perhaps it would have been best suited to defensive combat along a paved road, as paved roads would cause the fewest problems for moving this land-ship, and it could never be mobile enough to be an effective assault weapon. It would require a long, even, and accessible road. Perhaps the most suitable and nearest at that time would have been Nevsky Prospekt, in Leningrad, which is nearly six kilometers long. However, German boots never set foot in Nevsky Prospekt, but if they were to do so, the KV-VI could demolish entrenched positions on either side of the road at the same time. This could possibly have been appealing to Soviet leadership, as at Stalingrad, mere floors of buildings were fought over for days.
Kirov Plant in Leningrad would logistically be the best candidate for where this vehicle would be built, as it was very close to Nevsky Prospekt, and it spent the early war building KV tanks, but the blockade meant that there were few resources with which to build tanks. If Leningrad was able to get sufficient resources (which is an exceptionally big ‘if’) the KV-VI could possibly be sent along Stachek Prospekt passing by the Naval Triumph Arch, then on to Staro-Petergofskiy Prospekt, along Sadovaya Street, past Sennaya Square, and up to Nevsky Prospekt. It could then use the Palace Grounds to turn around, if necessary. Alternatively, the KV-VI could be sent via barge along the Neva River up to a temporary dock at the Admiralty Embankment or Palace Embankment, leading directly onto Nevsky Prospekt.
Instantly, problems with these theories arise. Firstly, the KV-VI would be incredibly vulnerable to any German aerial attacks, especially as the Red Army did not field any vast numbers of SPAAGs (or even fighter aircraft with which to defend against aerial attacks) during the war with which to defend such a high profile target. However, if the KV-VI were able to shoot down German aircraft, such as mentioned in the fake history, then it may be able to defend itself against lighter aerial attacks for a short time. Secondly, the assumption is that there would be sufficient resources for making the KV-VI, a suitable barge, and a temporary landing dock, which would, of course, never be possible at Leningrad until after the siege was broken, and even the probability of a barge or ship which can transport 138 tons being available is small.
Thirdly, the KV-VI making its way to Nevsky Prospekt via road would be incredibly difficult if any of the roads were bombed out, as it would need plenty of road space and a path that is as straight as possible. Also, the tram lines on Nevsky Prospekt would need taking down, or else face being destroyed by the KV-VI.
Finally, when several KV-2 and KV-1 tanks, a BM-13 Katyusha mounted on a T-60, and a few other light tanks would be far more efficient to design, build, battle, easier to transport, etc the KV-VI seems like a pointless endeavor in every manner – its only benefits would be its propaganda value, and its psychological impact on German soldiers.
Nevsky Prospekt as pictured during the war. It may have been one of the few places the KV-VI might see any real effective service, had it been invaded, and if the KV-VI were real.