In June 1941 Nazi Germany invaded the Soviet Union.
Thousands of German tanks and armoured vehicles poured across the border, engaging with the
waiting soviet armour in some of the largest tank battles in history.
In these early conflicts, despite the success of the T-34 and KV-1 and the tenacity of the
Soviet defence, the Germans came out on top – by a large margin.
This surprise attack would prove to be the spark that Soviet tank design badly needed,
and over the next few years they would develop some of the most impressive vehicles of the
war.
We all know about the T-34s, the KVs, and the IS-2, but there were a trio of vital anti-tank
and anti-infantry vehicles that are rarely talked about – the T-34 based SU series.
An issue that was brought up after the disastrous first few months of warfare was that Soviet
troops had no infantry support vehicles.
The T-34 and KV-1, while impressive, were only available in small numbers and were primarily
designed for anti-tank warfare, with the infantry relying on towed anti-tank weapons and field artillery.
Meanwhile, the Germans already had a 75mm armed support vehicle – the StuG III.
It used the chassis of the successful panzer III, but was cheaper, easier to build, and
mounted a bigger gun that was capable of lobbing 75mm high explosive shells at anything the defenders threw against it.
Very quickly, the Soviets decided they’d quite like a StuG of their own.
The first of the Soviet StuGs were literally StuGs – captured StuG IIIs pressed into
service with the Red Army by the Summer of 1941.
The issue was that ammunition was, naturally, quite hard to come by, and the Soviets began
to work on rearming their captured vehicles with domestic guns, namely the M-30, a 122mm Howitzer.
This project went quite well, and a prototype was ready by Summer 1942, known as the SG-122.
But, again, this vehicle would be completely reliant on the Red Army capturing intact,
functional StuGs consistently, which was unlikely to happen.
20 SG-122s would end up being completed, with up to 7 seeing combat in late 1942.
The Soviets by then had pivoted towards working on putting the M-30 onto the chassis of a
T-34, making their own StuG from the ground up using the lessons of the SG-122.
The new vehicle, known as the U-35, would keep the powerplant and transmission of the
T-34 with a new, casemate frontal hull, while still sharing more than 80% of components
with the T-34.
This hull would have the same 45mm thickness on the front as the T-34 but at slightly less
of an angle – 52 degrees instead of 60.
This would give it slightly less protection but provided a lot more interior space for
the crew.
The big, sloped sides of the vehicle would be a little different, with 45mm of protection
sloped at 18 degrees – a lot less protection than the T-34s 40mm at 40 degrees.
But, again, the crew needed room to lug 122mm shells about so it was more than acceptable.
The U-35 would be accepted into service in December 1942, as the SU-35.
However, production vehicles would fix some of the issues seen during testing the SU-35
and it would be known instead as the SU-122.
The SU-122 would blast into action on the 14th January 1943, proving incredibly effective
against infantry, emplacements and even armoured vehicles.
The 122mm howitzer wasn’t the most accurate, but if you could land a hit, it would be catastrophic,
and apparently could blow the turret clean off a Tiger under the right circumstances.
This 122mm was cumbersome though, and required the gunner, loader AND commander to operate
it, which wasn’t ideal.
The SU-122M and SU-122-III were prototypes using the smaller and more modern D-11 and
D-6 guns respectively, but these never reached production.
The SU-122 was usually deployed alongside another support vehicle, the SU-76.
This vehicle used the chassis of the T-70 light tank, and was armed, as per the name,
with a 76mm gun that was capable of both direct and indirect fire against infantry, emplacements
and even enemy armour.
However the Germans had introduced a tank that the 76mm gun couldn’t destroy – the
Tiger 1.
This meant that the tables had completely turned, with the KV-1, T-34 and SU series
unable to engage this German vehicle at anything more than point blank range, while the Tiger’s
88mm gun could despatch them all with ease from kilometres away.
The Soviets did have a gun that was up to the task, the 85mm D-5T, which had been adapted
from an anti-aircraft gun.
But there was absolutely no way the 85mm could be put into the turrets of a KV or a T-34
without an extensive redesign, so the decision was made to put it into the roomier casemate
of the SU-122.
I wish I had more to say about the conversion but it really was extremely simple.
Take one gun out and put the other in, with no other changes apart from, naturally, a
new mantlet.
The SU-85, as this new vehicle was known, would weigh around 30 tons and have a crew
of 4, with the 85mm gun being its only armament - a true anti-tank platform.
While only 638 SU-122s were ever built before the factory transitioned to the SU-85, the
new vehicle would be built in much larger numbers, with over 2,600 completed before
production ended in 1944.
The SU-85 would reach the frontlines in August 1943, just in time to be used in the battles
at Kursk.
The SU-85s would be dispersed along the front, being dispatched when the more heavily armoured
Tigers or Panthers were encountered.
By all accounts the vehicle performed well, essentially a less versatile T-34 with a lower
profile and a bigger gun.
With the introduction of the T-34-85 in the Summer of 1943, the SU-85 had sort of outlived
its usefulness.
These upgraded T-34s had the same firepower as the SU but had more armour and, of course,
a turret, with actual machine guns to boot.
But the SU series wasn’t dead yet.
The solution was to simply put a bigger gun into it.
Work began on this project, Object 138, in February 1944.
The new vehicle was set to use the D-10S, a 100mm anti-tank gun, and the chassis of
the SU-85 would be used to mount it, but this time there were some serious improvements.
Firstly, the armour of the vehicle was significantly thickened.
The SU-85 had 45mm of steel angled at 52 degrees, but the new vehicle, known as the SU-100,
would enjoy 75mm of armour at 52 degrees, meaning that it was essentially invulnerable
to the Panzer IV and StuG from normal combat ranges.
The second main difference was the appearance of a cupola for the commander.
This was integrated by adding a cylindrical bulge to the right side of the casemate, giving
the commander better vision out of the vehicle and adding a lot more room to his position.
While the SU-100 design was ready by mid-1944, the ammunition for the new gun was not, and
so around 300 early SU-100 hulls were fitted with the 85mm gun on the SU-85, being put into
service as the SU-85M.
When the ammunition was ready, the SU-100 itself took to the field in October of 1944,
just in time for the last big push into Germany, fighting all the way to Berlin.
And far beyond.
The SU-100 was blessed to use the same gun as the ubiquitous T-54 and T-55, meaning that
for the USSR and other Warsaw Pact countries, it was a very easy tank to keep around.
It was kept in production until 1947, with just under 5000 produced, and has an incredible
combat record, seeing service in the Suez Crisis, the Six-Day War and the Yom Kippur
war with Egypt and Syria, in the Korean war and the Vietnam war, two countries where it
is still in service today, and formed the backbone of China’s 1st Mechanised division.
It’s still in service in Morocco and in Yemen, seeing combat as recently as 2015 in
the Yemeni civil war.
The SU-122, 85 and 100 were not spectacular vehicles.
They weren’t the flashiest, didn’t get the most attention after the war, and aren’t
the huge late war behemoths that have everything beaten on paper.
But they were cheap, they were functional, and they allowed the Soviets to put relatively
big guns into service before there were more mature, capable platforms for them.
What’s not to like?
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