ISU-122 (China)

Description

The ISU-122 (Самоходная установка на базе танка ИС с орудием калибра 122мм, ИСУ-122) is a Soviet assault gun used primarily in anti-tank tasks during World War II. Unlike the ISU-152, the ISU-122 was primarily utilized for anti-armour missions with its 122 mm A-19 field gun, whereas the ISU-152 was used more for indirect fire support and anti-fortification operations with its devastating 152 mm ML-20S howitzer. Following the beginning of the Korean War, the Soviet Union committed to providing military assistance to China. China received 10 infantry division tank regiments from the Soviet Union in September 1950, with 300 T-34-85 medium tanks, 60 IS-2 heavy tanks, and 40 ISU-122 self-propelled artillery, as well as trucks and other support vehicles. More than 2,000 military vehicles were sent to China, along with three large and medium-sized repair factories and various ammunition.

Introduced in Update 1.91 "Night Vision", the ISU-122 is well-armoured and mounted with a 122 mm A-19 field gun. It has greater shell penetration and a slightly faster reload speed than the earlier ISU-152. On the right roof corner, a DShK heavy machine gun provides adequate deterrence against incoming planes and lightly armoured vehicles. Since both the 152 mm and 122 mm guns are installed on the same chassis, which was also utilized for the heavy tank IS-2, the other characteristics remain the same.

General info

Survivability and armour

The ISU-122 is inadequately protected against most enemy tanks. The vehicle is armoured mainly with 90 mm of rolled homogeneous armour (RHA), covering the sides, back and front glacis. The only thicker armour section (100 mm) covers the curved gun mantlet. Against tank guns, this level of protection is inadequate as the ISU-122's armour plates are all poorly angled and not of an enough thickness. The main frontal weakspot of the ISU-122 is the large piece of 90 mm superstructure armour plate and the lower front plate. These plates occupy most of the frontal silhouette, and a penetration through there is very fatal. Other areas are harder to penetrate: the huge spherical gun mantlet might bounce/absorb some shells sometimes (still, never rely on that), and the outmost side armour of the superstructure form a very steep angle, bouncing most projectiles. Against most SPAA the ISU has very reliable armour, as most SPAAs' penetration are lower than 60 mm. The top of the vehicle is armoured with 30 mm of RHA, meaning that common aircraft armaments (e.g. 12.7 mm M2, 20 mm MG 151, Ho-5) will not penetrate it with ease.

In terms of survivability, the ISU-122's five crew members are somewhat spread out, meaning that with a frontal penetration by an explosive-filled shell, the chances of an instant crew-knock are smaller. The large gun breech can also block some shrapnel for the crew on one side. But with a side shot through the superstructure, or if a large-calibre shell penetrates, the crew are very likely to get knocked out instantly.

Armour type:

• Rolled homogeneous armour
• Cast homogeneous armour (Gun mantlet)

Notes:

• Suspension wheels are 20 mm thick while tracks are 30 mm thick.

Mobility

Modifications and economy

Armaments

Main armament

The ISU-122, like the ISU-152, is a vehicle created by adapting an artillery field gun design on an armoured vehicle. The A-19 gun has the same good ballistic characteristics as the 122 mm on the IS-2 (flat trajectory, high muzzle velocity, accuracy at long range) and the same available ammunition choice.

The gun stays reliably accurate until 1,300 m distance. Beyond 1,000 m your optics will limit your accuracy as your magnification is poor (unless you fire at huge targets like Ferdinand, Jagdtiger, Tiger II, etc.). The high muzzle velocity of your shells grants you pretty flat firing trajectories and thus helps fire at moving targets from a distance. In that regard, using the "sight distance control" feature can increase your chances of successfully hitting enemy tanks.

The gun has a limited traverse on the horizontal axis. That displacement is asymmetrical due to the commander's position limiting rotation towards the left side. This can make the tracking of a target difficult as the gun quickly reaches a stop. You should take that constraint into account when positioning your hull at a firing spot.

Additionally, the rotation speed is very slow compared to other tanks at the same rank or battle rating who can aim their gun in average 2 to 3 times faster than you do. Which means your targeting process will be longer than for other tanks if you aim to be accurate. Any enemy appearing outside of the area your gun covers will require hull movement and will make you restart your targeting process from 0.

Being originally an artillery field gun, the gun uses two-piece ammunition with projectiles and propellant bags. The breech mechanism was not designed to be operated by a limited crew inside a casemate, which explains the very long reload time (between 19 and 26 seconds, which is on average 3 times longer than other vehicles' at the same BR).

Your recoil is important but not powerful enough to throw your gun off target after firing: the damping cylinders on the gun are too weak to absorb most of the recoil power and the suspension will absorb much of it. Your reload time being very long, the recoil is not as much of a handicap as it could be.

Ammunition

The available choice of ammunition focuses on heavily armoured targets:

• BR-471: APHE; an armour-piercing shell with high explosive mass and high muzzle velocity that will knock out any tank it penetrates with a single shot.
• BR-471B: APHEBC; the same as the BR-471 but with increased penetration thanks to the ballistic cap. This shell can reliably penetrate the frontal glacis of a Panther from over 700 m.
• OF-471: HE; for destroying open and lightly armoured vehicles. While it is a standard shell for a Soviet vehicle, prioritize using your heavy machine gun to deal with lightly armoured targets because of the long reload time of the ISU-122 (China).

Ammo racks

Ammo racks of the ISU-122 (China)

Notes:

• The ISU-122 (China) uses two-piece ammunition, composed of propellant bags (orange) and projectiles (yellow). Both have separate racks.
• To go into battle with the right flank depleted of propellant bags (racks 1 to 3), pack 17 (+13) shells.

Machine guns

The 12.7 mm DShK heavy machine gun is located on a pintle mount and can act as both an offensive and anti-aircraft machine gun on the ISU-122 (China), giving it protection against aircraft and lightly armoured vehicles. Best use is within 500 m against lightly armoured vehicles. The 360° movement allows you to point quickly your MG in any given direction. However, the position of the MG high on the casemate and the poor depression angle make it difficult to shoot a low-profile tank when it is close.

Usage in battles

Offensive role

The ISU-122 should be played as a long range sniper, taking advantage of the APHEBC shell's high penetration values, high gun accuracy and good reverse speed. Find a shooting spot and engage targets from at least 1,000 m away to prevent enemy progress towards the objectives. You will also suppress enemy fire to prevent your team from being pinned down by enemy snipers attempting the same in return. Because of your high profile (casemate) and weak frontal armour, always stay away from the frontline to avoid being flanked or swarmed. While your gun is very powerful, your in-game performance will highly be dependent on the map you're playing. Open maps like Fire Arc, Kursk or Maginot Line will allow to play at the full extent or your capability whereas urban environments like Advance to the Rhine will be detrimental to your playstyle. In case you are playing a mixed map, privilege open spaces.

Defensive role

In case of an enemy breakthrough, your role is to contain the enemy advance by pinning them down. The enemy will be moving the front line, so engagements will take place at a closer range than you're comfortable with. You should identify and target in priority choke points, narrow passages and corridors of the map that the enemy will be forced to take. Your limited gun traverse only allows you to monitor an area spanning 175 m at 1,000 m distance without having to reposition your hull. Position the left side of your casemate behind an obstacle to let only your gun exposed.

Other roles

If you try to use the ISU-122 in a different role on the battlefield, you will be confronted with the following:

• If you try to play as a front-line tank, you will be quickly disabled by any type of fire coming from enemy tanks. Your frontal armour is pretty thin for a tank at close range and a successful penetrating shot from the front will greatly handicap your crew sitting in line. Your gun traverse is very limited and your turning speed is also too poor to manoeuvre quickly enough in close combat.

• If you attempt to play support tank, your high profile will make it difficult to stay hidden behind obstacles without taking fire. Your good reverse speed can be an advantage but the enemy will flush you out with artillery strike (which can be accurate enough from middle ranges to disable you). Even with an escape route planned and cover to hide behind, your chances of survival are meagre. You will also be at risk of being flanked by light tanks or armoured cars, especially if they swarm you. Anyone who manages to get behind you has a very high chance to destroy you. In that role, an undetected flanking enemy, artillery strikes or CAS will be great threats to the ISU-122.

Notable enemies

• Any tank will disable you with little effort in a close range encounter because of your weak and vertical casemate armour.
• For long range engagements, the cannons able to penetrate an ISU-122 from 1,000 m are:
  • USA: M4 tanks equipped with a long 76 mm gun, M36 GMC
  • Germany: any vehicle equipped with a 75, 88 or 128 mm gun like Panthers. Tigers I, Sturer Emil, etc.
  • USSR: any vehicle equipped with a 85, 122 or 152 mm gun like the IS-2, T-34-85, ISU-152, etc.
  • Great Britain: any vehicle equipped with APDS like the Comet, Challenger, Centurion & Charioteer
  • Japan: Chi-Ri II & US tank imports
  • China: vehicles similar to US and USSR ones
  • France: ARL-44
  • Sweden: Ikv 103 & Strv 74

Differences between non-volumetric shells and volumetric shells hitting a Tiger I

An important note when engaging tanks, especially Tiger Is, is that, with the implementation of volumetric shells, you can no longer expect your shells to pierce through small openings or right past an obstacle. The large 122 mm calibre of your shells will result in it catching on an armour plate's edge very often, losing all of its penetration. For example, a Tiger I has some edges that can absorb your shell unexpectedly, despite having flat armour. Thus you must always make sure that where you are aiming at is absolutely free of obstruction, or it may result in a non-penetration or a ricochet. This can be seen in the diagram to the right.

Defeating an ISU-122

• Wait for ISU-122 to shoot before engaging it: its long reloading time is a big weakness as it is defenseless for at least 15 seconds like an IS-2. It can however retreat quickly thanks to its good reverse speed. Be careful not to get baited into open field trying to follow your prey.
• The ISU-122 has a rather thin armour when compared to tanks at the same BR: iIf you have a very high penetrating power, aim for the casemate.
• In a frontal encounter, the right side of the frontal armour plate is the biggest weak spot. A successful penetration will most likely knock out 3 out of 4 crew members because they sit in line along that axis.
• In a flanking manoeuvre, the center of the casemate is the place to shoot to knock most crew members out.
• From behind, the left side of the casemate is the best spot to disable the ISU-122.
• If you are alone, flanking a ISU-122 undetected remains your best chance to destroy it. But it is difficult because the ISU-122 ideally positions itself very far from the frontline.
• Force it out of position with indirect fire (artillery strikes) if you're at relative close range.
• In case of a frontal attack (choke point/corridor), try blinding the ISU-122 with smoke and then swarm it with several tanks to saturate its defensive capacities.
• Engage the ISU-122 while it is moving: it takes a long time to brake, turn, bring the gun to a stable position and target precisely. With a reload time over 15 seconds, no player will take a shot that has little chance to hit.
• Do not take pot shots or shoot on the move, aim precisely at the weak spots (casemate walls). Your chance of ricochet is increased at long range as your penetration power decreases and the ISU-122 can angle its hull in a defensive manoeuvre.

Pros and cons

Pros:

• Deadly cannon provides superior destruction capacity of any target upon penetration
• Powerful stock AP penetrates up to 205 mm which is very effective in a full up-tier; weak spots of the early Centurions, Ferdinand, Tiger II H can all get penetrated with ease
• The huge gun mantlet and its complex armour layout is capable of deflecting quite some shells sometimes
• 30 mm roof armour resists popular aircraft weapons well, like the 12.7 mm M2 with ground target belt and the MG 151
• All-round protection provides good resistance against flanking SPAAs; the M19 / M42 are very common flankers
• 14 km/h reverse speed allows it to retreat from danger quickly

Cons:

• Long reload of more than 20 seconds and the curved trajectory demands very precise aiming and can be a challenge to use for first-time users
• Front armour is only 60-100 mm and is not well-angled; easily penetrated by common guns at the battle rating, like the 76 mm M1, 17 pdr, 75 mm and 88 mm
• Closely packed crew all easily knocked out when an explosive shell penetrates
• Very inadequate gun depression of -3° combined with the sluggish mobility makes it only capable of fighting in urban (flat) areas, but never the hills
• Turretless layout and the sluggish mobility makes it very vulnerable to surprise flankers, for example, the infamous M18, T20, T25 and Puma
• Gun breech often gets damaged while under enemy fire

History

Development

When the ISU-152 began production in 1943 with the large 152 mm ML-20S gun, production of the chassis and hull soon exceeded the supply of the ML-20S gun, which caused a decrease in the production of self-propelled guns for the Soviet military. It was determined to speed up self-propelled gun production, the ISU chassis were to be mounted with the 122 mm A-19S gun. Work on this mounting already began before the supply issue in December 1943 at the Chelyabinsk Kirov Plant (ChKZ), which had a design team simply take the ISU-152 chassis and hull and only changing out the armament with the 122 mm gun, but this prototype - Object 242 - was not immediately put into production despite successful testings. When the supply issue arose, the prototype was then adopted by the Soviet Defense Committee for increased production and also that the 122 mm gun had better accuracy against tanks than the 152 mm gun. The ISU armed with the 122 mm gun, designated the ISU-122, began production in April 1944.

People's Liberation Army (PLA) service

40 ISU-122 self-propelled guns were delivered to the People's Republic of China (PRC) in 1950, forming a total of ten regiments along with a multitude of other Soviet armour. Each regiment had a total of four ISU-122s in it. At least 6 ISU-122 vehicles took part in a military parade in Beijing in 1954.

Media

Skins

• Skins and camouflages for the ISU-122 (China) from live.warthunder.com.

See also

Vehicles equipped with the same chassis

• ISU-122
• ISU-122S

Other vehicles of similar configuration and role

• ISU-152 · ISU-152 (China)
• SU-122P

External links

Paste links to sources and external resources, such as:

• topic on the official game forum;
• other literature.