T-34/SU-76 Hybrid

People’s Republic of Poland (1955)
Self-Propelled Gun – Probably Fake

The release of declassified historical documents from the archives of the United States Central Intelligence Agency (CIA) has produced some interesting, unusual, and often rather odd intelligence reports relating to tanks. With much of what was happening behind the Iron Curtain, especially in terms of military developments, being beyond the reach of agents and aerial photography, the CIA was often dependent on reports by intelligence operatives. Sometimes, these human intelligence sources were often untrained and unskilled reporters who may or may not even have had first hand experiencew wih what they reported onwards. The shady world of covert human intelligence operations is rife with misunderstanding and mistakes, and the more technical the topic, often the greater the mistakes. One report of exactly this type came out of Poland in May 1955 through the CIA, presenting some kind of SU-76/T-34 hybridized vehicle – whether the vehicle existed or not, is however, entirely speculative.

The Document

Any contemplation of the existence of this vehicle or what it might even have looked like begins squarely with the originating document from the CIA. Under “Tanks, Tank Equipment, and Other Equipment of the Polish Army” came a note on the SU-76 saying that lecturers at OCS (Officer Candidate School?) stated that the SU-76 was no longer in Soviet use and remained only in OCS-use as a training aid.

The mention that this information came from lecturers at OCS in Poznan almost certainly shows that this is first or second hand eyewitness evidence rather than just rumors. In other words, the information appears to have come from a lecturer at OCS or someone who spoke to one and then reported to the CIA.

The second part of the all too brief SU-76 bit mentions that there are two different types of SU-76 in use there for training. One was a standard SU-76 and the other is the oddity – an SU-76 mounted on a T-34 chassis.

“[Redacted] two types of the SU-76, one conventional and one mounted on a standard T-34 chassis. [Redacted] the latter was not a T-34/76 tank because it had an open fighting compartment”

The first part is simple enough. Retaining a vehicle which was still in service in one form or another for training or even just as an educational tool is perfectly normal. The SU-76 was no longer in production, but the T-34 was just entering Polish service at this time, providing an interesting crossover between the vehicles.

SU-76M

The SU-76M (the M is often dropped nowadays, as the original SU-76 saw little production and use) was quite a small vehicle, just 4.97 m long and 2.10 m tall, weighing under 11 tonnes. The vehicle only required 3 crew to operate it (commander, driver, and gunner), although two loaders were also usually present, and was really little more than a lightly armored platform (35 mm front armor on the gunshield and hull nose and 26 mm on the glacis) carrying the 76 mm ZIS-3Sh gun along with a single 7.62 mm DT machine gun. Widely produced and exported, the SU-76 was a common, simple, and effective mobile field gun which, thanks to its gun, also provided potent tank-killing capability.

The vehicles themselves first saw service with the Polish 1st Armoured Brigade in 1943 in the fight to drive out German forces with the help of the Soviet Army.

Firing a range of ammunition, from Armor Piercing High Explosive (APHE), Armor Piercing (AP), High Explosive (HE), and even High Explosive Anti-Tank (HEAT), the gun was still a potential threat on a Western European battlefield in the 1950s, even though it was, in all practical terms, an obsolete platform.

T-34

The T-34 is possibly one of the most famous tanks ever made and was produced in enormous numbers. This tank, perhaps more than any other, won the war for the Allies by providing a rugged, simple, well armored tank often superior or equal to the German tanks it faced on the Eastern Front. The subject of innumerable production changes, upgrades, modifications, and variants, the T-34 was, like the SU-76, widely exported both to Soviet satellite countries as well as countries outside Europe. Predominantly seen in two variants, the early 76 mm gun-armed version and, by 1945, predominantly the 85 mm gun-armed version with a larger and rounder turret, this tank was still a capable weapon system well after the war, although by the 1960s, it could be considered obsolete for frontline duty. Nonetheless, it would still be in many reserve units. In addition, it would also be a necessary and logical tank to have available at a training school.

Using a 38 liter water cooled V12 diesel engine developing 520 hp, the tank could manage up to 55 km/h on a road. Armament was concentrated in the turret with the 85 mm ZIS-S53 or D-5T gun and a 7.62 mm DT machine gun, with an additional 7.62 mm DT machine gun fitted in a bulge on the front right hand side of the hull, alongside the driver’s hatch. The vehicle reported in the CIA document is clearly turretless, so this would mean just a single machine gun was retained. The hull of the T-34 was both larger, heavier, and better protected than that of the original SU-76.

Polish units fighting under the command of the Red Army started receiving T-34s in 1945, with more arriving post-war and local production taking place between 1952 and 1956.

Comparison SU-76/T-34
Comparison SU-76/T-34	SU-76	T-34	Su-76/T-34 hybrid
Crew	5	4-5	est. 4-5
Length	4.97 m	6.68 m	6.68 m
Width	2.71 m	3.00 m	3.00 m
Height	2.10 m	2.45 m	2.45 m
Mass	10.5 tonnes	26.5 tonnes	est. 23 tonnes
Turret Armour	(casemate only – no turret)	Enclosed turret	(casemate only – no turret)
Front	35 mm rounded mantlet, 35 mm at 55º	60 mm (rounded)	35 mm rounded mantlet, 35 mm at 55º
Side	16 mm @ 65º	52 mm @ 30º	16 mm @ 65º
Rear	15 mm @ 70º	30 mm	15 mm @ 70º
Top	0 (open)	16 mm	0 (open)
Hull Armour
Front	25 mm @ 60º	45 mm @ 60º	45 mm @ 60º
Side	15 mm vertical	45 mm @ 40º	45 mm @ 40º
Rear	15 mm vertical	45 mm @ 48º	45 mm @ 48º

With no turret or gun, the T-34 would weigh substantially less than 26.5 tonnes, and even if the casemate from the SU-76 was added, it would still be lighter, as there was simply less added mass going back on. Depending on the variant of the T-34 and what motors, fittings, or other parts would be removed or modified during a creation of this type, the weight loss from a T-34 would have been up to around 5 tonnes. However, much of this weight would be added back on with the casemate and gun of the SU-76.

So What Was It?

The SU-76 and T-34 were substantially different both in stats and appearances. It is hard to imagine how someone with a modicum of knowledge on the subject could mistake the two. The SU-76 hull was small, with 6 small wheels, compared to the much larger T-34 hull with 5 large wheels.

If the report is taken at face value, and the vehicle was at least similar to the T-34’s hull with this open-topped SU-76-like feature added, what could it have been?

One possible explanation is the SU-100, a vehicle clearly visually the same to the T-34’s basic hull lines and dimensions. It had the same large 5 road wheels as the T-34 and a casemate built up over the hull. The Polish army had received some during April of 1945, with more arriving after the war. They were in service until the ‘60s.

On the face of it, this is perhaps the best candidate for mistaken identity, and the basic hull is as close as the report gets to a match. The casemate in no way looks similar in shape or style to that of the SU-76 and neither does the gun mount, as it lacks the large rectangular projection at the base. On top of this, the guns are wildly different. The SU-100 used a 100 mm D-10S gun over 5.6 m long with no muzzle brake, compared to the roughly 3.4 m long 76 mm ZIS-3sh on the SU-76, with a large and distinctive muzzle brake. There is also the obvious problem of the casemate not being open-topped on the SU-100, effectively ruling it out.

It is possible that it was something much more obscure, like the SU-100P, an open-topped vehicle on a vaguely similarly shaped hull. It had a different number of wheels (6 instead of 5), but at least had a muzzle brake. However, that vehicle was just a prototype, and it is hard to imagine why it might have randomly popped up in Poland long after it was redundant, not to mention the fact the gun was too long once more.

The final possibility is that this was a real vehicle, with a T-34 hull with a damaged turret being mated with a SU-76M superstructure, possibly from an SPG which had its hull damaged or destroyed. Such Frankentanks have appeared numerous times throughout history, and the construction of such a vehicle was definitely not outside the realm of posibility even for a regular tank batallion repair workshop. However, the question of what value such a contraption might have had for a training school remains unanswered.

Conclusion

Replacing the 85 mm gun from a T-34, a gun a field of fire of 360º thanks to being mounted in a turret, with the 76 mm ZIS-3Sh gun in a fixed casemate makes little sense from a combat point of view. Certainly, the gun switch would be a downgrade, adding nothing to the capability of the T-34 as a tank.

It would, however, be an upgrade for the SU-76. This would have been a bigger, heavier chassis on which to base the gun with more stowage space for ammunition, more armor (on the hull), and a top speed increased from around 45 km/h for the SU-76 to around 53 km/h for the T-34, and in this case, a slightly lighter T-34, so probably a little quicker still. Even so, there is no logic to try such an upgrade, and in fairness, the report does not discuss the vehicle as a combat vehicle, but as a training aid. As a training aid, maybe such a conversion made sense. It would have allowed tank driver training to be done with an actual tank whilst, at the same time, allowing for the basics of artillery training to be done with the SU-76 parts. Further, being open-topped would be more conducive to a school environment, whereby trainers could observe students, and indeed, the CIA report even confirms SU-76s being used for training roles at the school despite already having been withdrawn from service.

There is no good candidate for what the vehicle may have been, which leaves open the question of whether this SU-76 casemate on a T-34 hull really existed or was something else entirely. There are, of course, two simple answers, both of which meet the demands of Occam’s Razor. Either it never existed and the intelligence was wrong, or, the intelligence is correct and this was a simple training tool inside the OCS in Poznan. With the fall of the Iron Curtain in the 1990s, and the lack of subsequent corroborative documentation or photos of this vehicle, all that might be said of it currently is that it is conceivable that it existed.

Specifications T-34/SU-76 Hybrid
Crew	4-5
Dimensions	6.68 m Long, 3 m Wide, 2.45 m High, est. 23 tonnes
Armament	76 mm ZIS-3Sh gun along with a single 7.62 mm DT machine gun
Armor	Hull 45 mm, casemate, 35 mm at 55º on casemate front
Engine	38 liter water cooled V12 diesel engine developing 520 hp
Speed	est. 55 km/h

Sources

CIA Information Report 50X1 CIA-RDP82-00046R000400490004-0, dated 9th May 1955 https://www.cia.gov/readingroom/docs/CIA-RDP82-00046R000400490004-0.pdf