Several dozen other designs
Soviet artillery in the Great Patriotic War was respected by its opponents for the quality of its weapons, even if its tactics were derided for their infatuation with sheer volume of firepower. Mechanization of the Soviet artillery was delayed compared to the process occurring in other European armies of the time.
The history of Soviet armor is filled with complications because the same weapons and organizations often performed multiple battlefield roles - to include antitank, surrogate artillery, or infantry supporting assault gun. Another source of confusion is the use of labels or names like tank destroyer, generally acknowledged to be a tracked gun with tank-like armor protection.
In the name of the machine, the abbreviation SU stands for "Samokhodnaya Ustanovka" - self-propelled artillery mount, and the index, eg 122, is the caliber of the main armament of the machine. And the abbreviation ISU stands for "self-propelled installation based on the IS tank" or "IS-installation".
In 1929, the leadership of the Red Army came to the conclusion that it was necessary to create as many as two heavy self-propelled artillery triplexes. Hull, consisting of 107 mm cannon, 122 mm howitzers and 152 mm mortars on the chassis of a maneuverable tank (T-24 first, then T-28) and TAON triplex (special power heavy artillery), 152 mm long-range cannon, 203 mm howitzer and 280 mm mortars on the chassis of the prospective "positional" heavy tank. But, since there were no suitable chassis for such triplexes in 1929 (as well as parts of the artillery systems), the project was postponed for several years.
The Russians faced massive and skillful tank attacks; they responded by abandoning finesse and variety and concentrating on the volume of production of simple powerful guns. In the end it worked, and the Panzers were overwhelmed. Of particular note were the Soviet assault guns including the SU100 and SU122. In addition to an antitank role, this uniquely Soviet weapons idea provided accompanying fire support to attacking tanks or infantry.
The Soviet attraction to assault guns was as much due to cost and manufacturing considerations as tactical utility. An assault gun cost less than the turreted tank from which it was derived, but could mount a more potent gun with greater range, and often more protective armor as well. For example, the SU-76, which made up 57 percent of Soviet wartime assault gun production, was based on the obsolete T-70 light tank. Yet the automotive factories which produced the T-70 were not capable of manufacturing medium tanks. The SU-76 was developed initially as an expedient tank destroyer to take advantage of the automotive production facilities, but remained in production since it proved useful in providing infantry units with direct fire support in lieu of unavailable medium tanks. In this sense, it replaced the pre-war infantry tanks such as the T-26. Due to the open configuration of the SU-76M, it could be used in a traditional indirect artillery fire role even though this was seldom its mission.
On the broad category of antitank materiel in the War, it can be stated that the Soviets led, followed by the Germans who periodically surpassed them, then by the American tank destroyer attempts and then the British, who emphasized the tank.
An erroneous judgment may arise that self-propelled artillery mounts (ACS) based on the KV arose only as a response to the use of "Tigers" and "Panthers" by the enemy. So, SAU-152 (the number meant the caliber of the gun) even received the nickname "St. John's wort" in the troops. Installations, the production of which began in February 1943, already in the summer showed high efficiency in the fight against the enemy's tank "menagerie". However, Joseph Kotin conceived to create a similar ACS much earlier.
During the Soviet-Finnish war of 1939-1940, when the Red Army ran into the "Mannerheim Line" (a complex of defensive structures between the Gulf of Finland and Ladoga 132-135 km long), a heavy, well-armored self-propelled gun of 122 or 152 mm caliber was needed to suppress long-term firing points of the Finns. Kotin thought over the idea of ??increasing the mobility of heavy artillery, creating a "pillbox fighter" for about two years, starting this work in Leningrad and completing it in the Urals (where his SKB-2 was transferred). Strictly speaking, the "KV with a large turret" - aka the KV-2 with a 152-mm howitzer - can be considered Kotin's first assault self-propelled gun. They took part in the battles on the Soviet-German front from the beginning of the war, although they suffered from all the shortcomings inherent in the KV-1.
Without exaggeration, the ISU-122, ISU-152 (based on the IS-1 and IS-2, respectively) became excellent vehicles: reinforced frontal armor, a more reliable undercarriage (than the SAU-152) and specially designed cumulative ammunition.
In the first half of the Great Patriotic War, the Red Army experienced an acute shortage of anti-tank ACS. The first Soviet anti-tank self-propelled gun was the ZiS-30, built on the basis of the artillery archer Komsomolets and the powerful 57-mm ZIS-2 anti-tank gun . Adopted in the fall of 1941, this self-propelled gun proved to be a fairly successful anti-tank weapon. However, due to the shortage of the base chassis, it was possible to build only 101 ZiS-30 specimens. Therefore, by the summer of 1942, almost no ACS of this type remained in the troops, and until August the forty-third single ACS, which at least to some extent could be called anti-tank, was SU-122 . However, the 122 mm M-30 howitzer mounted on this self-propelled gun had an insufficient rate of fire and a low level of the trajectory of the projectile's flight, so that it was poorly adapted for firing at rapidly moving targets, although it had good armor penetration.
By August 1943, the new SU-85 self-propelled gun was developed. It used a D5S gun, created in a design bureau headed by FF Petrov, on the basis of an 85 mm antiaircraft gun. His armor-piercing projectile 53-BR-365 at a kilometer distance punched armor thickness of 102 mm, and the 53-BR-365P re-caliber projectile with a five-kilogram weight and an initial speed of 1050 m / s punched 103 mm. However, already at the time of its appearance, the SU-85 did not fully satisfy the requirements, which increased due to the appearance of Pz.Kpfw.V Panther and Pz.VI Tiger tanks, which were soon joined by Pz.VIB Royal Tiger. Therefore, almost immediately after the adoption of the SU-85 began the search for ways to enhance the firepower of SU-85.
The SU-85 and the later SU-100 were developed primarily as anti-tank vehicles and were deployed in anti-tank units. They were usually employed in the overwatch role, where their long range firepower was an asset, while their shortcomings such as the lack of a turret, were minimized. In an overwatch role, they would take up static position overlooking enemy positions as tank units advanced in front of them. From their positions, they could counter enemy anti-tank guns or tanks which were firing on the advancing Soviet tanks.
The heavy ISU-122 and ISU-152 were developed for the direct fire support role, with a secondary mission (in the case of the ISU-122) to counter German heavy tanks like the Royal Tiger which could not be dealt with by Soviet medium tanks like the T-34-85. Due to its closed configuration, these vehicles were not suited for use in traditional indirect artillery fire roles.
Much of what was said about ISU-152 can be repeated about ISU-122. However, there are significant features in this matter that should be considered more carefully. All variants of self-propelled guns of the ISU series can be classified both as heavy tank destroyers and as heavy assault guns. However, the emphasis regarding the combat use of these self-propelled guns was different for each vehicle: the ISU-152 was more inclined to the role of an assault gun, and the ISU-122 to the role of a tank destroyer.
In the army of Nazi Germany, the Jagdpanther was a tank destroyer of the same mass category as the ISU-122. There is no particular sense in comparing ISU-122 and Yagdpenter in detail: their guns were one of the most effective anti-tank weapons of their time. Those who wish to "work out" this issue in more detail can recommend an article on The Russian Battlefield, although it is dedicated to comparing the IS-2 base tank with the Pz Kpfw V, VIH and VIB. It describes the characteristics of the D-25T and KwK43 guns quite fully (which is almost equivalent to their versions for the self-propelled guns D-25C and StuK43). The shortcomings of the D-25S shells were more than more than “compensated” by the poor quality of the armor of German armored vehicles released in the second half of 1944 and later. Therefore, one should not especially “cling” to the numbers of armor penetration given in popular books and reference books - both guns could deactivate any model of enemy armored vehicles.
As for the ISU-122 as a heavy assault gun, then it, along with the ISU-152, had no analogues among serial models of German or Anglo-American armored vehicles in the same category by vehicle weight. The high-explosive fragmentation of the 122-mm cannon shell D-25C was strong enough to effectively hit the enemy’s living force hidden in trenches or buildings; however, its high initial velocity and lower elevation angle of the gun somewhat reduced its anti-personnel effect compared to howitzer shells of the same caliber. Therefore, in the fight against the entrenched infantry of the enemy, sometimes the average self-propelled howitzer SU-122 was more effective than the heavy ISU-122. In addition, the long overhang of the gun barrel of the ISU-122 sometimes made it very difficult to maneuver self-propelled guns in the cramped conditions of urban combat.
In 1943, assault gun production constituted only 17 percent of total Soviet armored vehicle production, in 1944 it peaked at 41 percent, and declined to 23 percent of total Soviet production in 1945.
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