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SU-85
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The SU-85 was a Soviet self-propelled gun used during World War II, based on the chassis of the T-34 medium tank. Unlike earlier Soviet self-propelled guns which were meant to serve as either assault guns or anti-tank weapons, this vehicle was a dedicated tank destroyer. The designation SU-85 is derived as follows: 'SU' stands for the - self-propelled carriage, while "85" signifies the bore of the vehicle's armament, the 85 mm D-5T gun.
Development history During the early phases of World War II, Soviet tanks such as the T-34 and KV-1 had sufficient firepower to destroy any German tank they encountered. However in the fall of 1942, Soviet forces encountered, for the first time, the new German Tiger tank. Tests of captured vehicles revealed the 76.2 mm guns used in the T-34 and KV tanks could only penetrate the Tiger's armor from dangerously short ranges. By spring 1943, the Soviets had also received reports of the new Panther tank, although the Panther was not seen in combat until July of 1943, during the battle of Kursk. The fielding of this new-generation of German vehicles meant that the Red Army required a new and more powerful anti-tank gun.
Testing indicated that the 122 mm M-30S howitzer mounted on the SU-122 self-propelled howitzer was ineffective against the Tiger I's armor, although it could penetrate the Tiger's armor by using HEAT rounds. The 122 mm gun’s low velocity, curved trajectory, limited ammunition storage and poor rate of fire made the SU-122 an easy target for the Tiger's 88 mm gun. Further tests showed that the best guns to consider for further development were the 85 mm 52-K anti-aircraft gun and the 122 mm A-19 field gun. In May 1943, a design bureau lead by chief designer Petrov was ordered to develop a new tank destroyer armed with this gun and utilizing a modified SU-122 chassis.
Simultaneously, the TsAKB (a design bureau a chief designer of which was V.Grabin) started design work on changing the armament of the SU-122 to the existing 85 mm S-18 gun, which was originally developed for KV heavy tanks. Since the gun was already nearing obsolescence, it was improved with a new mantlet and new gun cradle. After these improvements were carried out, the S-18 gun was delivered to the Uralmash factory. Initially the designers couldn't find a way to install the 85 mm S-18 gun in the casemate of the SU-122 because the size of the gun breech was far too big. Because of this Uralmash stopped design work on the vehicle because modifying the hull was extremely expensive at a time when simplicity and cheapness were very important to the Soviet military and heavy industry. Although the designers had mixed feelings about the vehicle they were supposed to design, the Soviet High command forced them to continue working on the project as they were desperate for anything that stood a chance against the new German tanks. Two quite different prototypes were built as a result of this. SU-85-I which was the first SU-85 prototype used a standard hull of the SU-122, but it was fitted with a new gun cradle and a new pig-nose-style ball mantlet for the gun. At first a coaxial machine gun was proposed to give the new vehicle some measure of protection from infantry attacks, but this was abandoned because of a lack of space. SU-85-IV which was the second prototype also utilized the SU-122 chassis, but it had a larger ball mantlet that was different from the one used in SU-85-I. Both prototypes used the problematic 85 mm S-18 gun.
At the same time work on mounting the 85 mm D-5S gun designed by Petrov into the casemate of the had SU-122 started. At first the D-5S gun was thought to be only a side project until the drawbacks of the S-18 were corrected. The two guns were entered into competitive trials in which the D-5S surprisingly showed not only the same ballistic capabilities as the S-18, but was also much more reliable. Although the D-5S gun successfully passed all of the state trials, the existing cradle of the gun made it impossible to fit a telescoping sight to it. To solve this problem a new sight was developed. It received a designation TSh-15. Another prototype was built. This one was armed with the D-5S gun and also utilized the new TSh-15 sight as well as a new ball mantlet design. It was designed SU-85-II, which apart from the new gun and a new TSh-15 sight, also introduced a new ball mantlet design. This prototype was put on comparative trials against the SU-85-I like the SU-85-IV was before it, which was abandoned because of several serious drawbacks. The SU-85-II proved to be superior to SU-85-I and therefore was accepted for service in the Red Army as the SU-85 tank destroyer after several changes which included changing the gun to D-5T.
In further design work aimed at improving the SU-85, the SU-85-III prototype was built. It had a modified commander's cupola.
Description The SU-85 was a modification of the earlier SU-122 self-propelled howitzer, essentially replacing the 122 mm M-30S howitzer of the SU-122 with a D-5T high-velocity 85 mm antitank gun. The 85 mm gun could penetrate the side armor of a Panther or Tiger at long range, and do so from a small, highly mobile vehicle with all-around armor protection. The new gun required a different mounting featuring a ball-shaped mantlet.
Production history SU-85 production started in mid-1943, with the first vehicles reaching their units by August. When the up-gunned T-34-85 medium tank entered mass production in the spring of 1944, there was no point in continuing production of a tank destroyer without superior firepower (Zaloga 1984:181, Perrett 1987:84), so SU-85 production was stopped in late 1944 after 2,050 vehicles had been produced. It was replaced on the production lines by the SU-100 tank destroyer, armed with the more powerful 100 mm D-10S gun.
There were two versions: the basic SU-85 had a fixed commander's cupola with a rotating periscope and three vision blocks; the improved SU-85M had the same casemate as the SU-100, with a commander's cupola as used on the T-34-85.
Service history
The SU-85 entered combat in August 1943. It saw active service in Soviet, Polish and Czechoslovak forces on the Eastern Front until the end of the war. It was obsolescent by 1945, and was withdrawn from active service not long after the war, to be exported to many Soviet clients states in Europe and elsewhere.
The SU-85 was used by Bulgaria, Romania, Hungary, Yugoslavia,, where it was withdrawn to reserve stocks by the mid-1980s, but remained in service longer in North Korea (Perrett 1987:84) and Vietnam (Perrett 1987:84). The similar SU-100 remained in service much longer, and some SU-85 and SU-100 were converted and used as command and recovery vehicles (Perrett 1987:85).
In addition to the Second World War, the SU-85 was used in combat by North Korea in the Korean War, by Egypt in the 1956 Suez Crisis, and by both Egypt and Syria in the 1967 Six-Day War (Perrett 1987:84).
Variants Former Soviet Union - SU-85-I - First SU-85 prototype with a standard hull of the SU-122 as well as a new cradle and a new pig-snout-type ball mantlet for the gun. Armed with 85 mm S-18 gun.
- SU-85-IV - Second prototype also with a standard hull of the SU-122 but it had a larger ball mantlet, different from the one used in SU-85-I. Armed with 85 mm S-18 gun.
- SU-85-II - Third SU-85 prototype with the new 85 mm D-5S gun, a new TSh-15 sight and a new ball mantlet design.
- SU-85 - Main production model armed with 85 mm D-5T gun.
- SU-85M - SU-85 with the casemate from the SU-100 tank destroyer, which was larger and could carry up to 60 rounds instead of 48. It also had the same commander's cupola as the one used in the T-34-85.
- SU-85T - SU-85 tank destroyer converted into an ARV.
- SU-85-III - Fourth SU-85 prototype with a modified commander's cupola, with direct vision slots and covers.
Poland - WPT-34 (1960s) - Polish repair and maintenance vehicle with a superstructure replacing the casemate, a crane, a large-diameter telescoping snorkel for deep fording operations as well as a large-spade type earth anchor in the rear. It was converted from SU-85 tank destroyers as well as T-34 medium tanks and SU-100 tank destroyers.
See also
External links
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