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Soviet Union's IS-1 heavy tank,
JS-1 heavy tank7:

IS-1 heavy tank with 85 mm:
Soviet Union's IS-1 Heavy Tank with 85 mm 		IS-1 heavy tank:
Soviet Union's IS-1 Heavy Tank		    

Design

IS stood for Iosef Vissarionovich Stalin.2

The need to increase the firepower of the KV series was seen by the end of 1942 with the Germans introducing Tiger tanks a new tank was needed to combat it.2

It was intended to be a 4-man tank, with an 85 mm gun, not weigh more than a KV-1, and that had thick enough armor to defeat the German 50 mm anti-tank gun.7

Based on the KV series it had a new hull, improvements in the suspension, transmission, and power train. The turret was cast and the hull had cast and rolled parts welded together.2

Design first started out with same 85 mm gun as the T-34/85 which was known as the IS-85 and a few were produced in late 1943. The cast turret (which was used in the KV-85) was designed by General A. A. Petrov.2 A heavier gun was needed as the T-34/85 was being produced and having a heavy tank with the same armament as a medium was thought to be inefficient. The 100 mm designed by V. Grabin was tried with great success and known as the IS-100.2 The 122 mm was tried but it was only a little more effective, however the 100 mm was in short supply. The superstructure extended out over the tracks and this allowed for a bigger turret.5

There was no MG in the hull which allowed for a better ballistic shape.5

Prototype

A design bureau was headed by N. F. Shashmurin at Tankograd in the Urals that developed the IS series.2 By the end of 1943 prototypes were available.2

Only a short test was done and the State Defense Committee approved the tanks for use in the Red Army in October 1943.2

Production

After a few models were produced, production was switched to the IS-2. The models that were left were converted to IS-2 standards.

Variants

Usage

Some saw action in the Ukraine in early 1944.

  IS-1, IS-1 (85)8 IS-1 19432, IS-1A5 IS-1B5, IS-1 (122)8
Crew 43,4,5,6,7,8 42,5 45,8
Physical Characteristics      
Weight 97,000 lb,
44 tons4,6,8, 45.3 tons3,7
46,000 kg3,7
44 tons2 44.5 tons8
Length w/gun

27.3'4,8, 27' 3"3,7, 29' 4"
8.32 m3,7, 8.56 m6

8.56 m2 31' 6"8
Length w/o gun   6.77 m2  
Height 8.9'4,8, 9' 6"3,7
2.735 m6, 2.9 m3,7
2.73 m2 8.9'8
Width 10' 3"4,8, 10' 8"3,7, 11'
3.07 m6, 3.25 m3,7
3.07 m2 10' 3"8
Width over tracks      
Ground clearance 0.47 m6 0.46 m2  
Ground contact length 14.3'8
4.3 m6 		  14.3'8
Ground pressure 0.78 kp/cm2 6 0.78 kp/cm2 2  
Turret ring diameter      
Armament      
Main 85 mm3,4
85 mm M19438
100 mm7 		85 mm M1943 D-5 T2
85 mm or 100 mm5 		122 mm5
122 mm M19438
Secondary      
MG 2: 7.62 mm DT MG3
4: MG4
2: 7.62 mm MG7
3: 7.62 mm MG8 		  3: 7.62 mm MG8
MG - coaxial   1: 7.62 DT MG mm2  
MG - rear   1: 7.62 DT MG mm2  
MG - hull   1: 7.62 DT MG mm2  
MG - antiaircraft 1: 12.7 mm DShK8   1: 12.7 mm DShK8
Side arms      
Quantity      
Main 718 592 288
Secondary      
MG 1,3308 2,5202 2,3308
Side arms      
Armor Thickness (mm) 1327, 30 - 1323, 19 - 1204    
Hull Front, Upper 120 - 1606, 1208 120 - 1602 1208
Hull Front, Lower      
Hull Sides, Upper 89 - 908, 906 902 89 - 908
Hull Sides, Lower      
Hull Rear 606 602  
Hull Top 258, 306 20-302 258
Hull Bottom 258 20-302 258
Turret Front 30 - 1008 1002 30 - 1028
Turret Sides   902  
Turret Rear   60-902  
Turret Top   302  
Engine (Make / Model) V-2-IS3,7, V-2-IS (V2K)8 W-2-IS2
(V-2K)		 V-2-IS (V2K)8
Bore / stroke   4 stroke2  
Cooling      
Cylinders 127,8 V-122 128
Capacity      
Net HP 5107, 5134,8 600@2,000 rpm2 5138
Power to weight ratio 11.8 hp/ton6 14.1 hp/ton2  
Compression ratio      
Transmission (Type)      
Steering      
Steering ratio      
Starter      
Electrical system      
Ignition      
Fuel (Type) Diesel4,7,8   Diesel8
Octane      
Quantity   800 liters2  
Road consumption      
Cross country consumption      
Performance      
Traverse 360°    
Max speed 23 mph4,8, 24.8 mph3, 24.9 mph7
37 kph6, 40 kph3,7
37 kph2 23 mph8
Cross country speed 15 mph    
Road radius 149 miles, 150 miles8, 155 miles3,7
250 km3,7, 130 - 240 km6 		150 km2 150 miles8
Cross country radius 130 miles8
110 - 125 km6 		  130 miles8
Turning radius      
Elevation limits      
Fording depth 1.3 m6 1.3 m2  
Trench crossing 2.5 m6 2.5 m2  
Vertical obstacle 1 m6 1 m2  
Climbing ability   30 - 36°2  
Suspension (Type)      
Wheels each side      
Return rollers each side      
Tracks (Type)      
Length      
Width 2' 1.63"8   2' 1.63"8
Diameter      
Number of links      
Pitch      
Tire tread      
Track centers/tread      

Sources:

  1. Russian Tanks of World War II Stalin's Armored Might, by Tim Bean & Will Fowler, 2002
  2. Russian Tanks and Armored Vehicles 1917-1945, by Wolfgang Fleischer, 1999
  3. The Encyclopedia of Tanks and Armored Fighting Vehicles - The Comprehensive Guide to Over 900 Armored Fighting Vehicles From 1915 to the Present Day, General Editor: Christopher F. Foss, 2002
  4. Tanks of the World, 1915-1945, Peter Chamberlain, Chris Ellis, 1972
  5. Tanks of World War II, Duncan Crow, 1979
  6. Russian Armour Volume 1: The IS Tanks IS-1, IS-2, IS-3, Mikhail Baryatinskiy, 2006
  7. The Illustrated Guide to Tanks of the World, George Forty, 2006
  8. Airfix Magazine Guide 22 Russian Tanks of World War 2, John Milsom and Steve Zaloga, 1977
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