ISU-122
Encyclopedia
The ISU-122 was a Soviet
self-propelled gun used during World War II
.
, Russia), in December 1943. The design shared the chassis of the ISU-152
self-propelled gun and differed only in armament, having an A-19S 121.92-mm gun as its main weapon instead of the ISU-152's ML-20S gun-howitzer. Towed versions of these guns used the same carriage: 52-L-504A (Russian designation 52-Л-504А), so installation of an A-19 instead of an ML-20 gun was not a difficult task. After completing development of the ISU-152, ChKZ engineers mounted the A-19 gun on the ISU-152
chassis to create "Object 242" — the first ISU-122 prototype. It was successfully tested but not immediately launched into mass production.
At that time all ISU hulls were being equipped with the ML-20S gun-howitzer, but the production of hulls increased quickly and there was a lack of ML-20S tubes in the beginning of 1944. State authorities ordered these uncompleted hulls armed with an A-19 gun (specifically with the A-19S variant, slightly modified for the self-propelled gun mount). A further advantage of rearming the ISU was increased direct fire range against heavy German tanks. For these reasons the State Defense Committee adopted Object 242 for Red Army
service as the ISU-122 on 12 March 1944. In April 1944 the first series ISU-122 left the ChKZ production lines.
The A-19S gun had a manual-piston breech, which reduced the rate of fire to 1.5 from 2.5 shots per minute. Soviet designers developed the D-25 by modernizing the A-19S's breech, creating a semi-automatic variant of the 121.92-mm gun. The D-25 gun was installed in IS-2 tanks as a priority, but in September 1944 became available for self-propelled guns. The prototype ISU vehicle, armed with a D-25S was designated "Object 249" and successfully passed plant and state testing. The fire rate was improved to 2 to 3 shots per minute and with two strong experienced loaders the rate of fire reached 4 shots per minute. Due to the muzzle brake reducing recoil forces the D-25 had a smaller recoil buffer than the A-19. This improved the crew's work conditions and allowed for a smaller, lighter gun shield with the same armour thickness.
After testing Object 249 was immediately launched in mass production as the ISU-122S (ИСУ-122С) self-propelled gun. However, the original ISU-122 remained in production (along with the ISU-152
) due to a large stock of A-19 guns (the ML-20 and D-25 came directly from artillery factories). Mass production of the ISU-122 and ISU-122S ceased at the end of 1945. ChKZ produced 1,735 ISU-122 and 675 ISU-122S variants in total.
After World War II, many surviving ISU-122s were rebuilt as rocket launchers, very large calibre gun chassis or supply vehicles. The small number of ISU-122s which kept their original armament were modernized in 1958. This modernization was not as complete as that of the ISU-152. Most ISU-122s did not receive a new engine, only upgraded gun sights and radio sets. In the beginning of 1960, the ISU-122 was withdrawn from Soviet Army service (the ISU-152 served much longer). Some disarmed ISU-122s were transferred to civil organizations, to be used as emergency vehicles on Soviet railways or as tracked transport in Arctic areas of the Soviet Union.
Some vehicles were fitted with a 12.7 mm DShK
anti-aircraft machine gun.
In later models the A-19 gun was modified to have a semi-automatic breech block. This gun was designated D-25S, and the vehicle mounting it ISU-122S. The modification increased rate of fire from 1.5 rounds/minute to 3 rounds/minute. The ISU-122S variant is recognizable by its ball-shaped gun mantlet
and double-baffle muzzle brake
.
is the same except for the gun mounting, sights and ammunition stowage. The A-19S or D-25S cannons of the ISU-122 had 18 degrees elevation angle and 30 rounds of ammunition (the ISU-152 had 20 degrees and 20 rounds respectively). The A-19S cannon was equipped with an ST-18 (СТ-18) telescopic sight and the D-25S cannon was equipped with a TSh-17 (ТШ-17) sight. Both types of sights had maximal exact targeting distance of 1.5 km (the ISU-152 could manage only 900 m). Maximum direct fire range of the A-19S or D-25S cannons was 5 km, much further than these sights' targeting abilities. For direct or indirect firing on distances over 1.5 km the gunner used the second, panoramic sight.
The crew of the ISU-122 was 5 men and their location and roles were identical to those of ISU-152 crewmen. The ISU-122S was used with either 4 or 5-man crews since the semi-automatic breech allowed for a reasonable fire rate with a crew of four; the place of the absent loader was often taken up with additional ammunition. With a five man crew (two loaders) the ISU-122S demonstrated a better fire rate than with four men.
. Soviet Army commanders tried not to mix the ISU-122 and the ISU-152 in one regiment or brigade, although there were some units equipped with both types. The different armament of the ISU-122 and the ISU-152 caused problems with ammunition supplies and logistics. Another disadvantage of mixed-type units was a doubling of the calculations required for massed indirect fire.
, the same as with the SU-152
and ISU-152
heavy self-propelled guns in general. However these vehicles differed in their combat use. The primary application of the ISU-122 was as a tank destroyer, while the SU/ISU-152 tended more towards the assault gun role. With the same hull as the IS-2 the ISU-122 had good armour performance but more importantly very good performance with high-explosive rounds. The 121.92-mm gun had great potential, although the gun's abilities were somewhat reduced by the available projectiles and its lack of accuracy. In 1944 the BR-471 was the sole armour-piercing round available (the Germans had armour piercing rounds also, including ballistic nose and sub-caliber variants). An improved version, the BR-471B (БР-471Б) was developed in early 1945, but was available in quantity only after World War II ended. In extremis the ISU-122 engaged enemy heavy armour with OF-471 (ОФ-471) high explosive projectiles. These shells had a mass of 25 kg, a muzzle velocity of 800 m/s, and were equipped with a 3 kg TNT charge. Mechanical shock and explosion was often enough to knock out enemy AFVs without any armour penetration.
For urban combat ISU-122's were utilized as assault guns, but with a lower efficiency in comparison to the SU/ISU-152. In general Red Army commanders viewed the ISU-122 as a good assault gun. The OF-471 projectile was powerful enough against unprotected and entrenched infantry, pillboxes, and fortified buildings. In urban combat the long barrel of the 121.92-mm cannon sometimes made maneuvering difficult.
Use of the ISU-122 as a self-propelled howitzer was rare, although its maximum range of fire exceeded 14 km. Usually the ISU-122 delivered indirect fire to the enemy during rapid advances when support from towed artillery was not available.
s. ISU 122s can be seen in the museums of the Russian Central Artillery and Engineer Troops in St Petersburg, the Kubinka Tank Museum
, the Central Museum of the Russian Army, the Museum of the Great Patriotic War, Kiev
and other tank museums and World War II memorials in Poland
and Belarus
.
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
self-propelled gun used during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
.
History
A prototype of the ISU-122 (in Russian ИСУ-122) heavy self-propelled gun was built at the Chelyabinsk Kirov Plant, (Chelyabinskiy Kirovskiy Zavod (ChKZ), ChelyabinskChelyabinsk
Chelyabinsk is a city and the administrative center of Chelyabinsk Oblast, Russia, located in the northwestern side of the oblast, south of Yekaterinburg, just to the east of the Ural Mountains, on the Miass River. Population: -History:...
, Russia), in December 1943. The design shared the chassis of the ISU-152
ISU-152
ISU-152 was a Soviet multirole fully enclosed and armored self-propelled gun developed and used during World War II, with a subsequent use, mainly in the Soviet military, till the 1970s.-History:...
self-propelled gun and differed only in armament, having an A-19S 121.92-mm gun as its main weapon instead of the ISU-152's ML-20S gun-howitzer. Towed versions of these guns used the same carriage: 52-L-504A (Russian designation 52-Л-504А), so installation of an A-19 instead of an ML-20 gun was not a difficult task. After completing development of the ISU-152, ChKZ engineers mounted the A-19 gun on the ISU-152
ISU-152
ISU-152 was a Soviet multirole fully enclosed and armored self-propelled gun developed and used during World War II, with a subsequent use, mainly in the Soviet military, till the 1970s.-History:...
chassis to create "Object 242" — the first ISU-122 prototype. It was successfully tested but not immediately launched into mass production.
At that time all ISU hulls were being equipped with the ML-20S gun-howitzer, but the production of hulls increased quickly and there was a lack of ML-20S tubes in the beginning of 1944. State authorities ordered these uncompleted hulls armed with an A-19 gun (specifically with the A-19S variant, slightly modified for the self-propelled gun mount). A further advantage of rearming the ISU was increased direct fire range against heavy German tanks. For these reasons the State Defense Committee adopted Object 242 for Red Army
Red Army
The Workers' and Peasants' Red Army started out as the Soviet Union's revolutionary communist combat groups during the Russian Civil War of 1918-1922. It grew into the national army of the Soviet Union. By the 1930s the Red Army was among the largest armies in history.The "Red Army" name refers to...
service as the ISU-122 on 12 March 1944. In April 1944 the first series ISU-122 left the ChKZ production lines.
The A-19S gun had a manual-piston breech, which reduced the rate of fire to 1.5 from 2.5 shots per minute. Soviet designers developed the D-25 by modernizing the A-19S's breech, creating a semi-automatic variant of the 121.92-mm gun. The D-25 gun was installed in IS-2 tanks as a priority, but in September 1944 became available for self-propelled guns. The prototype ISU vehicle, armed with a D-25S was designated "Object 249" and successfully passed plant and state testing. The fire rate was improved to 2 to 3 shots per minute and with two strong experienced loaders the rate of fire reached 4 shots per minute. Due to the muzzle brake reducing recoil forces the D-25 had a smaller recoil buffer than the A-19. This improved the crew's work conditions and allowed for a smaller, lighter gun shield with the same armour thickness.
After testing Object 249 was immediately launched in mass production as the ISU-122S (ИСУ-122С) self-propelled gun. However, the original ISU-122 remained in production (along with the ISU-152
ISU-152
ISU-152 was a Soviet multirole fully enclosed and armored self-propelled gun developed and used during World War II, with a subsequent use, mainly in the Soviet military, till the 1970s.-History:...
) due to a large stock of A-19 guns (the ML-20 and D-25 came directly from artillery factories). Mass production of the ISU-122 and ISU-122S ceased at the end of 1945. ChKZ produced 1,735 ISU-122 and 675 ISU-122S variants in total.
After World War II, many surviving ISU-122s were rebuilt as rocket launchers, very large calibre gun chassis or supply vehicles. The small number of ISU-122s which kept their original armament were modernized in 1958. This modernization was not as complete as that of the ISU-152. Most ISU-122s did not receive a new engine, only upgraded gun sights and radio sets. In the beginning of 1960, the ISU-122 was withdrawn from Soviet Army service (the ISU-152 served much longer). Some disarmed ISU-122s were transferred to civil organizations, to be used as emergency vehicles on Soviet railways or as tracked transport in Arctic areas of the Soviet Union.
Variants
DShK
The DShK 1938 is a Soviet heavy machine gun firing the 12.7x108mm cartridge. The weapon was also used as a heavy infantry machine gun, in which case it was frequently deployed with a two-wheeled mounting and a single-sheet armour-plate shield...
anti-aircraft machine gun.
In later models the A-19 gun was modified to have a semi-automatic breech block. This gun was designated D-25S, and the vehicle mounting it ISU-122S. The modification increased rate of fire from 1.5 rounds/minute to 3 rounds/minute. The ISU-122S variant is recognizable by its ball-shaped gun mantlet
Gun mantlet
A gun mantlet is an armour plate or shield attached to an armoured fighting vehicle's gun, protecting the opening through which the weapon's barrel projects from the hull or turret armour and, in many cases, ensuring the vulnerable warhead of a loaded shell does not protrude past the vehicle's...
and double-baffle muzzle brake
Muzzle brake
Muzzle brakes and recoil compensators are devices that are fitted to the muzzle of a firearm or cannon to redirect propellant gases with the effect of countering both recoil of the gun and unwanted rising of the barrel during rapid fire...
.
Construction and design
Construction of the ISU-122 and ISU-152ISU-152
ISU-152 was a Soviet multirole fully enclosed and armored self-propelled gun developed and used during World War II, with a subsequent use, mainly in the Soviet military, till the 1970s.-History:...
is the same except for the gun mounting, sights and ammunition stowage. The A-19S or D-25S cannons of the ISU-122 had 18 degrees elevation angle and 30 rounds of ammunition (the ISU-152 had 20 degrees and 20 rounds respectively). The A-19S cannon was equipped with an ST-18 (СТ-18) telescopic sight and the D-25S cannon was equipped with a TSh-17 (ТШ-17) sight. Both types of sights had maximal exact targeting distance of 1.5 km (the ISU-152 could manage only 900 m). Maximum direct fire range of the A-19S or D-25S cannons was 5 km, much further than these sights' targeting abilities. For direct or indirect firing on distances over 1.5 km the gunner used the second, panoramic sight.
The crew of the ISU-122 was 5 men and their location and roles were identical to those of ISU-152 crewmen. The ISU-122S was used with either 4 or 5-man crews since the semi-automatic breech allowed for a reasonable fire rate with a crew of four; the place of the absent loader was often taken up with additional ammunition. With a five man crew (two loaders) the ISU-122S demonstrated a better fire rate than with four men.
Organisation
The organisation of military units utilizing the ISU-122 was the same as with the ISU-152ISU-152
ISU-152 was a Soviet multirole fully enclosed and armored self-propelled gun developed and used during World War II, with a subsequent use, mainly in the Soviet military, till the 1970s.-History:...
. Soviet Army commanders tried not to mix the ISU-122 and the ISU-152 in one regiment or brigade, although there were some units equipped with both types. The different armament of the ISU-122 and the ISU-152 caused problems with ammunition supplies and logistics. Another disadvantage of mixed-type units was a doubling of the calculations required for massed indirect fire.
Combat history
The ISU-122 was used as a powerful assault gun, a self-propelled howitzer, and a long-range tank destroyerTank destroyer
A tank destroyer is a type of armored fighting vehicle armed with a gun or missile launcher, and is designed specifically to engage enemy armored vehicles...
, the same as with the SU-152
SU-152
The SU-152 was a Soviet heavy self-propelled heavy howitzer used during World War II.It mounted a 152 mm gun-howitzer on the chassis of a KV-1S heavy tank. Later production used IS tank chassis and was re-designated as ISU-152...
and ISU-152
ISU-152
ISU-152 was a Soviet multirole fully enclosed and armored self-propelled gun developed and used during World War II, with a subsequent use, mainly in the Soviet military, till the 1970s.-History:...
heavy self-propelled guns in general. However these vehicles differed in their combat use. The primary application of the ISU-122 was as a tank destroyer, while the SU/ISU-152 tended more towards the assault gun role. With the same hull as the IS-2 the ISU-122 had good armour performance but more importantly very good performance with high-explosive rounds. The 121.92-mm gun had great potential, although the gun's abilities were somewhat reduced by the available projectiles and its lack of accuracy. In 1944 the BR-471 was the sole armour-piercing round available (the Germans had armour piercing rounds also, including ballistic nose and sub-caliber variants). An improved version, the BR-471B (БР-471Б) was developed in early 1945, but was available in quantity only after World War II ended. In extremis the ISU-122 engaged enemy heavy armour with OF-471 (ОФ-471) high explosive projectiles. These shells had a mass of 25 kg, a muzzle velocity of 800 m/s, and were equipped with a 3 kg TNT charge. Mechanical shock and explosion was often enough to knock out enemy AFVs without any armour penetration.
For urban combat ISU-122's were utilized as assault guns, but with a lower efficiency in comparison to the SU/ISU-152. In general Red Army commanders viewed the ISU-122 as a good assault gun. The OF-471 projectile was powerful enough against unprotected and entrenched infantry, pillboxes, and fortified buildings. In urban combat the long barrel of the 121.92-mm cannon sometimes made maneuvering difficult.
Use of the ISU-122 as a self-propelled howitzer was rare, although its maximum range of fire exceeded 14 km. Usually the ISU-122 delivered indirect fire to the enemy during rapid advances when support from towed artillery was not available.
Surviving examples
Most of the ISU-122s produced survived the Second World War and examples remain, but only a few of the surviving ISU-122s kept their initial appearance. Many were rebuilt or scrapped in the mid 1960s. The number of ISU-122s preserved in museums and memorials is substantially lower than surviving ISU-152ISU-152
ISU-152 was a Soviet multirole fully enclosed and armored self-propelled gun developed and used during World War II, with a subsequent use, mainly in the Soviet military, till the 1970s.-History:...
s. ISU 122s can be seen in the museums of the Russian Central Artillery and Engineer Troops in St Petersburg, the Kubinka Tank Museum
Kubinka Tank Museum
The Kubinka Tank Museum is a large museum of armoured fighting vehicles in Kubinka, just outside Moscow. It has many famous tanks from World War I, World War II and the Cold War. The museum also houses many unique vehicles, such as the Panzer VIII Maus, Troyanov super-heavy tank and a Karl-Gerät...
, the Central Museum of the Russian Army, the Museum of the Great Patriotic War, Kiev
Museum of the Great Patriotic War, Kiev
The National Museum of the History of the Great Patriotic War is a memorial complex commemorating the German-Soviet War located in the southern outskirts of the Pechersk district of Kiev, the capital of Ukraine, on the picturesque hills on the right-bank of the Dnieper River.The museum has moved...
and other tank museums and World War II memorials in Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
and Belarus
Belarus
Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...
.
See also
- List of Soviet tanks - covers all periods
External links
- ISU-122 on BattleField.Ru
- ISU-122 on Vasiliy Chobitok's ArmorSite (articles by A. Meretzkov and A. Sorokin)