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Soviet IS-2 Heavy Tank

Picture 1:
Early in the autumn of 1943, the
Soviets were completing the first of
three prototypes of their new IS-1
(IS-85) heavy tank using design
experience gained from their
previous KV heavy tank projects.
These new IS (Iosef Stalin)
prototypes were systematically
demonstrated before the special
commission from the Main Defense
Commissariat and with the
completion of general factory trials
the IS design was approved for
production. Although the first
production vehicles mounted the
85mm gun also seen on the T-34/85
medium tank, these initial IS-1
tanks were shortly converted to
carry the 122mm M1943 D-25 gun

before they were provided to the tank troops. The new IS-2 tank weighed little more than its predecessor KV tank, but it had
thicker and better-shaped armor that provided vastly improved protection. The overall weight was kept low by using a more
compact hull and component design, as we shall see later. Once the 122mm gun was installed and series production continued,
the new "Tiger Killer" was officially named the IS-2 Heavy Tank, although its weight and armor characteristics closely
coincided with the German Panther medium tank. By the end of 1943, the Kirov Factory had produced a total of 102 IS-2 heavy
tanks and they were used for the first time in February of 1944 at Korsun Shevkenskovsky. Although there were a number of
external improvements to the IS-2 during its production and field use, there were relatively few internal changes made over the
years.

Our internal exploration of the IS-2 will center around large color drawings loaned to us by Valera Potapov that appear in his
excellent web site

The Russian Battlefield

and photographs taken by Steve Zaloga inside an IS-2m.

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Picture 2:
This is the first of Valera's web site drawings, this one showing the basic exterior design of both the hull and turret for an early/
mid production IS-2 (please notice that the web address on these pictures for his site has changed; the link I provided above will
take you to the new site). The IS-2 hull was designed after ample combat experience with the KV tanks, and you can see that the
hull actually overhangs the tracks. It is an interesting hull design in that the bow casting is welded directly to a circular casting
for the base of the turret. Additional rolled armor plates are then added to form the rest of the hull sides, ending at a sloping rear
plate that covers the engine and transmission. Both heavy armor castings and rolled plate are utilized in the hull, and the castings
in the bow provide around 122mm (4.7in) of frontal armor. This initial bow design was based on the earlier KV-13 tank layout.

Although the first IS-2 vehicles used this curved and gently sloping front bow casting, it was later replaced in 1944 with either a
new casting or a welded plate nose, both of which had a straight 60-degree slope from glacis to the top of the hull. The Uralsky
Factory of Heavy Machinery (UZTM) plant made the welded noses, while factory #200 made the cast types. The IS-2 was one of
the first production Soviet tanks to remove the traditional second driver/hull machine gunner from the bow of the tank, providing
additional space for fuel tanks. In place of a ball mounted MG on the front plate, a DT machine gun was mounted on the right
side of the hull behind the driver and up near the turret ring. It was fired via a remote control firing cable from the driver's
position.

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Picture 3:
The new tank design illustrates the Soviet's mid-war combat strategy reorientation from using tanks for infantry assault to tank
hunting and killing machines. As a result, the second driver in the hull was deemed unnecessary and the crew was reduced from
the traditional five soldiers to only four, the driver then placed in a central position in the bow. The commander is located inside
the turret at the left rear, the gunner is to the left of the main gun, and the loader is to the right. Both the gunner and loader are
provided with over-head periscopes and the commander has a non-rotating turret cupola incorporating vision blocks that
provided a 360-degree field of view. He also has a rotating periscope in his cupola hatch. A round roof hatch that is flush with
the turret roof is provided for the loader on his side of the turret.

Initially, the 122mm L/43 gun mounted in the cast turret retained its original interrupted screw breech, showing its ancestry from
the already proven D-19 field gun. But the screw field gun breech was replaced (by early 1944) with a horizontally sliding block,
semi-automatic type, and of course the recoil cylinders and elevating mechanisms were altered from the field gun to fit into a
turret. Because the 122mm ammunition rounds were so huge, they were provided in separate pieces, a projectile and a charge
cartridge, but even so only 48 complete rounds could be stored inside the tank. Although a number of ready rounds were
strapped into easily reached racks in the turret, most of the ammo was stored in sheet metal boxes down on the hull floor and, as
we have seen in the T-34/76, these boxes were often covered with rubber floor mats. There was no turret basket in the IS-2; the
turret crew seats were either suspended from the turret and rotated along with it (commander's) or the seats were supported on
tubes that rose from the center of the floor and also rotated with the turret (gunner and loader).

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Picture 4:
By the time the IS tanks were being manufactured, the Soviets had plenty of technical experience with casting large pieces of
armor, and the IS-2 turret became one of the biggest castings they manufactured during the war. Although Western writers have
tended to criticize the coarse standard of Soviet armor finish, the urgency of tank manufacture in 1943 did not warrant lavishing
extra time and energy on unnecessary refinements. Over the course of its production, the turret was gradually changed. The early
IS-2 tanks that were manufactured in 1943 were originally designed to have installed a D-5T 85mm gun in their turrets, and they
had a narrow opening for the telescopic sight just to the left of the gun. When the 122mm D-25T gun was placed inside these
same turrets, it was very hard for the gunner to use his telescopic sight, as it was so close to the gun. So, in mid-1944 a new turret
with a larger sight opening that was also shifted slightly to the left was produced. Also at this time the thickness of the turret's
mantlet was increased, along with the lower hull sides. The new turret also moved the commander's cupola slightly to the left and
the gunner's PT4-17 periscopic sight in the turret roof was changed over to a Mk.4 type. About this time a Model 1938 12.7mm
DShK anti-aircraft machine gun was installed outside on the commander's cupola to provide some protection from strafing
German aircraft.

This drawing shows the general arrangement of projectile storage in the turret bustle, where many AP-T and HE-Frag projectiles
were stowed. There are also a couple of brass charge cartridges strapped down horizontally on the right turret lip, as well as a
pistol port and storage for flair pistol rounds up on the right turret wall. Down on the right track sponson are additional
horizontally stowed charges while the seat for the commander at the rear of the turret ring is shown folded up on the turret lip
under the 7.62mm DT machine gun that was initially mounted in the bustle. The gunner and loader's seats are supported on
hollow tubes that rise from the center of the floor and rotate with it. The V-2IS, four-stroke, V type, 12-cylinder engine is located
in the rear of the hull, and in this drawing some of the firewall separating the fighting compartment from the engine compartment
is visible. The diesel engine produced around 520hp to push the tank a maximum of 23mph on the road and roughly 18mph cross
country. Maximum range with the internal fuel was 150mi.

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Picture 5:
Stripping away the rest of the turret and some additional portions of the hull provides this view of additional internal components
of the IS-2. In the turret area you can now see the support tubes for the gunner and loader's seats, as well as a part of a third tube
(conduit) carrying electrical and radio wires up to the turret equipment. Down below the seats are some of the sheet metal
storage boxes for shell charges, and a starting crank handle is visible on the firewall at the rear. Up forward is the central driver's
position, flanked by the two large diesel fuel tanks, although additional fuel tanks are located in the rear on either side of the
engine. Total fuel inside the tank was around 137gals, but additional fuel and oil drum tanks were normally lashed to the sides of
the engine compartment. The oil drums were particularly important as the V-2 engine used huge quantities of oil.

Along both hull walls, just behind the driver, are two sets of vertical storage racks for more brass charge cartridges, although
only the rack on the right side of the hull is drawn here. As we have found in many Soviet WWII tanks, the V-2 diesel engine
could be started with compressed air in very cold weather, and the air storage cylinders are located up in front of the driver. A
DT machine gun is shown located in the right forward hull, but back directly under the turret ring. I have to admit that I had
never noticed this weapon before in photographs of the IS-2, but as I researched images for these pages I found the MG
mounting on many early IS-2 tanks. Curious.

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Picture 6:
Now the engine and rear mounted transmission are visible, as well as a number of the yellow compressed air tubes and other
control lines from the driver's area to the rear of the hull. The engine setup is very similar to what we have seen in the medium
tank T-34, in that the engine is attached directly to the multiple dry main clutch, which is then attached to a scirroco cooling fan,
which then attaches directly to the mechanical gearbox and differential. The gearbox provides eight forward gears and two
reverse. The water radiator originally designed for the KV-13 predecessor of the IS-2 is an interesting design. Also used in the IS-
2 tanks, it was in the shape of a horseshoe and efficiently covered the sides and top of the large cooling fan. The steering brakes
and final drives are mounted on either side of the transmission, and the rear mounted drive sprockets are attached to the final
drives. Also visible here are the torsion bars of the suspension, again this was one of the first Soviet tanks to utilize the German
developed torsion bar suspension which was also to be seen in other Allied tanks by the end of the war. You see the torsion bars
running in pairs across the hull floor because each bar enters the hull from a road wheel station and then crosses the hull to attach
to the opposite wall.

Picture 7:
Now, through the courtesy of Steve
Zaloga, we will slide down into an
IS-2m that he photographed while
at the Duxford Museum in England.
These photos were taken with a
very wide-angle lens, which allows
us to view a good portion of the
interior components but also
slightly distorts the edges of the
photographs somewhat. In this
case, we are at the rear of the
fighting compartment, just in front
of the firewall, looking forward
toward the central driver's position.
The IS-2m, or IS-2 Model 1944,
was the vehicle's name given when
the front bow armor was changed to
a straight slopping plate, the
gunner's PT-4-17 periscope was

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replaced with the Mk.4, the wider
turret mantlet was substituted, and

the 12.7mm DShK heavy machine
gun was mounted on the turret cupola. Our first picture above shows an IS-2m although the DShK is not mounted.

Directly in front of us is the combination seat support and electrical collective ring, the gunner and loader's seats supported on
the two tubes painted white with the hinges at the bottom, allowing them to swing under the gun breech and to be out of the way
when necessary. The third tube contains wires for the radio and electrical components in the turret, the conduit rising from the
collective up to the turret lip near the gun mount. On the floor surrounding the tube supports and collective are a number of
stowage boxes for 122mm ammo. Also down there are two darker colored battery boxes, one at either side of the floor, near the
sponson walls. Just forward of the battery boxes are the vertical brackets for storing charge cartridges that we saw in earlier
drawings, there were approximately five charges in each rack.

The large boxes on either side of the driver's seat are the diesel fuel tanks we saw in a previous drawing, and the steering levers
and gearshift are also visible near his seat. The driver has three viewing devices, two rotating periscopes at either side of his
position, and one episcope mounted directly on the front armor plate in front of him. As far as I can tell, the driver has no exit at
his position so he must crawl back into the fighting compartment to enter and leave the vehicle via the turret. The huge underside
of the 122mm breech ring is at the top of the image with some of the traverse gearing visible to either side. To the right and just
below the turret ring you can see the black mounting ring for the forward facing DT MG, but the MG is missing.

Picture 8:
Stefan Kotsch sent us a few drawings of
Soviet machine guns, this one illustrating
the 7.62mm DT 1929, used in the IS-2 as
the hull MG as well as the coax. Notice
that unlike the infantry version (known as
the DP-- the 'T' in DT stands for tank),
the DT MG has a retractable metal stock
in place of the wooden one, and also now
has a wooden pistol grip. The drum
magazine was typically used in Soviet
tanks and the drum held 60 rounds in two
layers, therefore making it thicker than
the drum used with the DP version.
Normally, a separate optical sight (1 and
2) was mounted when the DT MG was
installed inside a tank.

Picture 9:
Here is an enlargement of the previous photo emphasizing the
driver's area in the bow. Steering was via a regenerative two-
stage system with skid turns, and the levers could be locked in
any position. Full back lock on both levers effectively placed the
brakes into the parking position. The gearshift lever is to the
driver's right and is mechanically connected to the synchromesh
transmission (or manual gearbox, sources vary on this point) at
the rear of the tank. Above the gearshift is the driver's primary
instrument panel and electrical switch/fuse box, and a radio
connect box for him is also visible. Notice that you can now see

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the ends of two dark compressed air cylinders under the forward
episcope. And although you can't see them from this angle due
blockage by the driver's seat back, there are traditional brake and
clutch pedals down on the floor in front of the seat. Also up there
is a back-up hand pump for the compressed air cylinders.

Picture 10:
This is the view looking forward to the gunner's seat from the
commander's position-- the commander's cupola is visible directly
above us. The typical 10RK radio transceiver and intercom system is to
our left, and a number of racks for 7.62mm DT MG ammo drums can
be seen down on the sponson to our left and on the other side of the
radio. Directly forward from our position is the dark gunner's seat with
his elevation and traverse hand wheels, and the D-25T gun breech is
visible to our right. The commander's cupola is non-rotating, but the six
vision blocks are spaced so an almost complete 360degree view is
provided. There are protective face pads around each cupola block and
shattered glass blocks can be easily replaced by opening the latch under
the frame. Normally, a rotating periscope is also mounted in the center
of the cupola hatch over our heads. On the turret ceiling, just forward of
the cupola, is a Soviet interior dome light, typically with a blue lens
installed.

Total production of the IS-2 tank amounted to around 2,250 vehicles by
the end of the war. Of these, approximately 250 were reported to have
been constructed in the first quarter of 1944, 525 in the second quarter,
725 in the third, and 750 in the last. When the first IS-2 tanks rolled off
the factory floor and out the door, they were placed in special new units
designated as separate Guards heavy tank regiments (OGTTP). These
units typically had 21 IS-2 tanks divided into four companies with five
tanks each. The Guards units were also known as "break through"
regiments indicating their powerful offensive design.

Picture 11:
Turret traverse was either manually by hand or powered with
an electric motor, the hand wheel can be seen on the left. Gun
elevation was via the darker handle you see in the center of the
enlarged photo and it was manual only. There was no
stabilization on these guns and the laying equipment was fairly
simple and simple to operate and maintain.

Visible down on the floor between the elevation hand wheel
and the gunner's seat is this side's vertical storage rack for
122mm charges that we saw earlier, and also a storage rack for
MG ammo drums is at the lower left. Up in the turret we can
just see that storage rack for additional MG ammo drums seen
earlier, along with the gunner's radio connection box for his
headset and microphone. The periscope in the roof is the later
Mk.4 type while the 10-T-17 telescopic sight is directly in front
of us and has the forehead pad adjusted to view through the
sighting ocular with our left eye.

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The over-head dome light now dominates the top of the photo,
and some of the left side of the huge green breech ring is
visible to our right. Laying on top of the flat ring is the black
breech actuating handle, and if you look carefully just forward
of the handle you can barely see the two recoil cylinders laying
on top of the gun tube. The gun can be fired either electrically
via the thumb button on the traverse wheel, or mechanically by
the lanyard you see hanging in front of the gun shield, just to

the lower right of the elevation hand wheel. Elevation of the big gun was from -3 to +20 degrees.

Picture 12:
Another of Steve Zaloga's photos illustrates some of the equipment on
the loader's side of the turret in this preserved IS-2m. The black electric
turret ventilator is at the upper left over the gun, and one of the recoil
cylinders is visible up near the gun mount/mantlet. To the right of the
gun tube is the mount for the 7.62mm DT coaxial MG, which is not
mounted in this vehicle. The loader's Mk.4 roof periscope is to the right
of the ventilator and further right is another interior dome light.
Forward of the periscope is another vertical rack for four DT MG
ammo drums and below the rack is the electric motor and gearing for
powered traverse. Notice the thin drive shaft arriving from the manual
hand wheel on the other side of the weapon and here entering the
gearbox in front of us. The small radio connect box on the turret wall
under the dome light is for the loader. At the end of this wire is the plug
that attaches to his helmet lead, and the plug is neatly tucked into the
leather pouch you see on the turret wall to the right of the control box.
Down on the hull floor are more of those green 122mm ammo boxes
and the vertical rack for a few charge cartridges on this side of the
forward hull are seen under the turret traverse motor.

When the Soviets tested their D-25T gun against a captured Panther
tank, the 122mm gun manufactured at factory #9 easily "penetrated"
the Panther's frontal armor at 2,500 meters. The Soviet report states that
the gun's ballistic characteristics were identical to those of the A-19
122mm field gun, the D-2 122mm gun (factory #9), and the S-4 gun

(Central Artillery Design Bureau), giving it a muzzle velocity of 780-
790m/s with a 25kg projectile. I suspect the Panther in question was not "penetrated" by an AP-T round, as it did not have the
kinetic energy at this velocity and range, but instead the Panther probably had its armor shattered by a HE-Frag projectile.
Maximum range for the D-25T weapon was stated to be over 3,000 meters, but of course accuracy at that distance was totally
nonexistent due to the variations in ammo and gun barrels, and the lack of sufficiently precise Soviet sighting equipment. Most
records indicate that tank duels took place well under 1000 meters in WWII, and at that range the D-25T's AP-T probably would
indeed penetrate the Panther's front plate, particularly those made from 1944 on with homogenous armor.

Picture 13:
This interior picture shows the rear of the
turret with racks for both AP and HE
projectiles. The typical AP-T projectile used
in the IS-2 was the BR-471B and the HE-
Frag was OF-471N. Since the AP projectile
was shorter it was stored in the rack at the
right and the HE in the left rack. As far as
the charge cartridges are concerned, both
types were made from brass and were the
same general shape with little of any
narrowing near the cardboard plug at the
end. But the charge casings for the armor-

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piercing BR-471 projectile had a red
identification band around the case near the
black lettering. Notice how the upper
bracket supports for the projectiles may be
adjusted in height along the vertical support
rods. The recoil guard for the 122mm gun
almost touches the rear of the turret lip and
there is a secondary guard mounted on its

left rear corner to protect the commander over in his position. The recoil guard obscures the commander's seat. Back further in
the commander's corner of the turret is the rear DT MG mount and the commander's radio connect and control boxes are also
seen mounted to the wall. Up in the cupola you can just see the bottom of the periscope mounted in the hatch. I believe that that
is a padded black canvas Soviet tanker's helmet laying on the projectile rack, complete with the radio connect plug hanging
down.

Picture 14:
If we stand up in the commander's position with the hatch
open, we would have access to the 12.7mm MG up on his
cupola. This is another drawing sent to us by Stefan
Kotsch, this one showing how the MG was mounted and
the anti-aircraft sight was used at the end of the war, and
beyond. The DShK was the standard Soviet heavy
machine gun for most of the war, used as the standard
infantry gun as well as secondary armament on their
larger armored vehicles. The gun was a joint design
project by both Degtyarev and Shpagin. The feed
mechanism was very unique-- a rotary block which was
protected by a steel stamping, was positioned above the
breech mechanism. When the cartridges were stripped
from the links in the belt, they were revolved around the
block and inserted into the chamber.

Picture 15:
The external appearance of the DShK resembled the DS machine gun,
with spade grips, trigger mounted on the back plate, and barrel with
cooling fins and large muzzle brake welded to the end of the muzzle.
The anti-aircraft sights replaced the standard leaf rear sight when
mounted on tanks, the AA sight being either the M1938 or M1941
type. They were both said to be suitable for firing at rapidly moving
surface and air targets.

By 1943, the Soviet DShK had been in wide use for some time, and
there were complaints of breakages and feed problems coming in from
the using troops. To help remedy the problems, the revolving feed
mechanism was removed and a simpler setup, using a claw to pull the
cartridge out of the belt and present it in front of the bolt, was
installed. Some other parts were also strengthened and simplified. The
new model became the DShKM (sometimes with "38/46" added
behind the M), the M referring to "Modernized". In this guise, the
trusty MG served on with Soviet forces well after WWII, with many
still in service today.

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Picture 16:
Two IS-2m tanks stand ready as their
crews listen to instructions from a Soviet
officer. All the tankers seem to be
wearing the late war, black leather, 3/4
length jacket over their khaki coveralls.
The photo appears to have been taken in
Berlin in 1945 at the end of hostilities,
and the white stripe on the farthest IS-
2m turret was an Allied identification
marking introduced at this time to help
Allied aircraft avoid attacking
unfamiliar Red Army tank formations.
Our Picture 1 is taken in a similar setting
but in a more severely damaged section
of the city.

Again, I would like to thank Valera
Potapov of

The Russian Battlefield

for

the use of his drawings of the interior of
the IS-2, as well as Steve Zaloga for
loaning us his interior photographs of

the IS-2m. Steve's images can also be seen in a number of his own publications on Soviet/Russian armor, including the New
Vanguard series of Osprey Publishing's "IS-2 Heavy Tank 1944-1973" and Concord Publications Company's "Stalin's Heavy
Tanks 1941-1945, The KV and IS Heavy Tanks". Also I would like to thank Stefan Kotsch for the machine gun sketches. We
have plenty of room for additional images and reference information about the interior of the IS-2 in these pages. Please feel free
to contact me if you care to contribute.

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