Saturday 23 November 2019

Long Awaited Tank Destroyer

History often moves in a spiral. The story of Soviet medium SPGs illustrates this fact well. In the summer of 1940, when development of SPGs on the T-34 chassis began, a tank destroyer was one of them. In the spring of 1942, the concept of the SPG changed, and the SU-122 was born. However, in May of 1943 a mobile means of defeating enemy tanks in the medium weight category was needed. On August 8th, 1943, more than three years after the request for a medium tank destroyer came through, the SU-85 was finally accepted into service with the Red Army. How well did Soviet industry deal with the vehicle that came to replace the SU-122, and how did it perform the tasks given to it on the battlefield?

Gradual transition

GKO decree #3892ss "On organization of production of the 85 mm SPG on the T-34 tank chassis at the Uralmash factory" issued on August 8th, 1943, did not give UZTM much time. Production of the SU-85 had to start on August 25th, and 100 had to be delivered by the end of the month. The plan for September increased to 150 units. UZTM still had to deliver 25 SU-122s in August, in addition to T-34s.

Factory #9 was instructed to supply 110 D-5-S-85 guns in August to enable this. The first guns had to arrive at UZTM by August 23rd. 170 guns were awaited in September.

The volumes and deadlines stated here seem very harsh. UZTM never produced more than 100 SU-122s per month. In addition, the factory often worked in emergency conditions. The problem was with irrational arrangement of production at UZTM and ChKZ. Stalin's demand to radically increase T-34 production led to entirely unaffiliated factories having to pick up the shortfall.

ChKZ was forced to reduce heavy tank production in favour of the T-34. It was even tougher than the SU-152 was added to the mix in the spring of 1943. Production of three vehicles at the same time (T-34, KV-1S, SU-152) proved challenging for the factory. Recall that in 1943 ChKZ produced 4 types of heavy tanks (KV-1S, KV-85, IS-85, IS-122) and two types of SPGs (SU-152, ISU-152). No tank factory in the world had to deal with such a horror.

Assembly of the first SU-85s, August-September 1943. The vehicle bears many slogans, including "To defeat the Tigers!"

The UZTM was also not doing well. The factory had much less power than ChKZ, and launch of the SU-122 into production was a serious trial. Not a single month in 1943 ended without an emergency. The factory either did not give enough SU-122, or not enough T-34s, or the quota was not filled for either. Something had to change, and GKO decree #3892 freed the UZTM from having to produce the T-34. Production at this factory never crossed 100 tanks per month, and threatening the very necessary SU-85 to produce such a small amount of tanks was senseless. It is also possible that this decision was made in connection with the return of V.A. Malyshev to the post of People's Commissariat of Tank Production. Stalin removed him from this position in the summer of 1942 specifically because of insufficient T-34 production.

UZTM delivered its last 9 T-34s in August.

A completed initial production SU-85.

The harsh deadlines had an effect on the choice to replace the SU-122. All three vehicles tested by the military were found unsatisfactory. To make work faster, the SU-85-I, SU-85-II, and SU-85-IV were built on the SU-122 chassis, mandated by GKO decree #3289 issued on May 5th, 1943.

However, UZTM was aware of the cramped fighting compartment of the SU-122. Gorlitskiy proposed that the UZTM should be given the task of developing a SU-85 with a widened fighting compartment by September 1st, 1943. This proposal was accepted, and the Department of the Chief Designer (OGK) of the UZTM developed this variant by the end of September. However, work did not proceed past drafts. The SU-85 that entered production was not much different than the SU-85-II.

Changes affected the gun mount, which was hurriedly improved at the factory #9 design bureau, as well as the gun shield and mantlet. The fuel system and electric equipment were improved, the panoramic sight hatch was enlarged by 100 mm to the right and 150 mm back. The commander's cupola received additional armour and the sight in it moved forward by 30 mm and 100 mm to the right. The gun port in the front armour changed to be like the one on the SU-122M, the pistol port on the right side was moved. The crew of the SU-85 also consisted of only 4 men.

The word "batch" is rarely used to refer to SU-85 production. The first batch was composed of pilot vehicles, late ones were not split into batches. Gorlitskiy proposed that a modernized vehicle would enter production later, but this never happened.

The SU-85 looked like this starting with the second half of September of 1943. The "brows" of the pistol ports are gone, the lifting eyes of the gun mantlet are different.

Like the GKO decree instructed, assembly of the SU-85 began in late August of 1943. By the 26th two vehicles were completed and entered trials. 200 shots with each gun were planned, but in practice gun #105 fired 251 times and gun #11 fired 300 times. The SPGs passed trials, but there were complaints about the gun shield that fouled the "pocket" of the mantlet. This increased the effort it took to move it. The commission composed a list of changes that would have to be made to September vehicles.

One vehicle passed 300 km mobility trials. The other was disqualified at 235 km when a water pump broke. Both SU-85s showed issues with road wheel rims. The SU-122 and T-34 exhibited the same issues.
A train with the first SU-85s, fall 1943.

The decision to put the SU-85 into production without serious changes saved a lot of time. The decision to stop parallel production of the T-34 also helped. The factory met its quota: 100 SU-85s were delivered by September 1st. The cost of one SPG was the same as one SU-122: 166,500 rubles.

The rate of production was affected by slow ramp-up of D-5S-85 gun production at factory #9. 10 SU-85s passed mobility trials in the first 10 days of September, of which only 26 had guns. However, by September 20th the factory delivered 83 SPGs and 152 in all of September, 2 more than required by quota. Even though the situation with guns repeated itself in October, the factory delivered 162 SPGs, again surpassing the quota by 2. In November the guns came gradually, instead of in bursts, and 166 vehicles were delivered instead of 165. In December the quota was also overfulfilled: 176 instead of 175. UZTM went from lagging behind to outstanding performance.

The situation with quality also improved. SU-85 #U309274 built in September of 1943 completed 1000 km trials with an average speed of 29.1 kph on a highway and 17.9 kph off-road. Inspection after trials showed that the engine and transmission are ready for further use. The weakest link was the road wheels. One broke due to the external ball bearing, another due to the rim peeling. Similar road wheel defects were encountered at other factories. Overall, the SU-85 was the most reliable Soviet SPG built at this time.

An improved gun mount approved for production in September 1943.

This didn't mean that the SU-85 had no issues. Both results of QA trials and reports of military representatives reflect this. Of 100 SU-85s assembled in August, Engineer Lieutenant Colonel G.Z. Zucher found only 54 defect free. The same situation occurred in September. Assembly was to blame for some defects but a number of them were due to the design. One of them was the attachment of a massive gun shield with only four bolts. This was not enough, and the shield began to sag after intensive shooting.

The factory tried to combat this defect by replacing one of the two shock absorbers with a metal liner, but it was clear that a new part needed to be designed. A new shield that was held by 6 bolts was approved on September 16th, 1943. This part was installed on production SPGs starting with the 95th produced in October.

The trigger mechanism changed even earlier, in September. This was also a problem part. On August 28th, 1943, a new commander's cupola was approved with sides strengthened to 45 mm. This got rid of the applique armour. The new cupola was introduced into production on September 20th, 1943. The location of the toolbox changed on September 1st, 1943. The left side ammunition rack also changed at this time. On October 1st a handle was added near the commander's cupola to make his work easier.

The lifting eyes of the gun mantlet also changed in September-October. Initially they were built as welded-on hooks, like on the SU-85-II. Later they were produced as loops, cast as one with the mantlet. The exhaust fan on the roof disappeared, it was replaced with a two-piece ventilation hatch. Interestingly enough, at least one production vehicle has this fan. When it appeared and how many vehicles were built with one is a mystery. The table of changes introduced into production does not have this novelty.

As of October 8th, 1943, the SU-85 was produced with a torsion bar compensator for the improved driver's hatch. These hatches were distinguished from the T-34's hatch with a C-shaped marking.

The SU-85  looked like this by the end of 1943. The gun shield is held by 6 bolts, new hand rails and additional track links on the front are installed.

The biggest change made in November of 1943 was the addition of spare track link holders on the front of the hull. The first vehicles to receive them were those produced on November 20th. On the same day, the panoramic sight hatch received torsion bars, which made it easier to open. The air engine starter was changed in November, and a drain for the gun mantlet "pocket" was added to get rid of water collecting there. The shape of the upper and lower front plate connecting beam changed some time in November. Instead of a round shape, it was closer to a triangle. This change was also not present in the list of changes introduced into production.

The design of the hand rails on the sides and rear of the casemate as well as the engine deck was radically simplified in December of 1943. The pistol ports were also simplified, the visors were now gone. There were no more noticeable visual changes in the SU-85, although development continued.

Adapting to production

UZTM overfulfilled the quota in January of 1944, delivering 176 SU-85s. In this month the subcontractor managed to fulfil their quota. By the morning of February 1st 165 guns were delivered. However, there were some complaints about them. For instance, the NIBT Proving Grounds returned one, complaining about a loose barrel. This resulted in high dispersion during shooting.

Factory #8 also received an order for D-5S-85 guns in late December of 1943, and two factories began producing guns for the SU-85 starting with January 1944. By February 1st, factory #8 built 36 guns and delivered 12. Factory #9 aided in organizing production. Factory #8 developed their own variant of the gun, indexed D-5S85A. The first such gun was assembled in late January.

This is what the SU-85 looked like by the spring of 1944. The SU-85A was not visually distinct.

Production of the "regular" D-5S-85 gun at factory #9 did not stop. The reason for this was pragmatic: factory #8 also built 52-K AA guns. The breech and barrel were used from them. The D-5S85A also used a different recoil guard than the D-5S85. Military representative Zucher was against this solution, as it introduced confusion in spare parts kits. Nevertheless, the D-5S85A passed trials in an SU-85 and was green lit for production.

An electric firing mechanism was tested in January of 1944. It was scheduled to go into production in February of 1944. Another novelty was the installation of two fans in the roof of the fighting compartment. This solution did not go into production. The price of a SU-85 increased to 185,000 rubles.

The last significant changes to the SU-85: shorter hand rails and shifted right hand pistol port.

The plan for production of the SU-85 was the same in February as January: 175 units. 54 were built by February 10th, 112 by February 20th. However, instead of the 200 guns the factory was supposed to receive, only 37 arrived. The factory only received the necessary guns by the end of the month, and the quota was overfulfilled again: 176 vehicles. Factory #9 delivered 139 guns that month and factory #8 delivered 42, some of the D-5S85A. The SPGs with this gun were indexed SU-85A. In March UZTM received 102 D-5S85 and 89 D-5S85A. 191 vehicles produced in March of 1944, 112 were SU-85 and 79 were SU-85A.

The situation with two guns that had the same purpose but non interchangeable barrels, breeches, and recoil guards was hard to call normal. An order was given to cease production of the D-5S85 at factory #9. This was done due to the fact that the T-34-85 was changing over from the D-5T to the S-53 designed by the Central Artillery Design Bureau (TsAKB). Of 200 SU-85s delivered in April, 175 were SU-85A. In May, all 205 vehicles were SU-85A. In June UZTM reached peak production, completing 210 SPGs. This rate of production was held all summer. The decision to free UZTM from T-34 production was wise.

The same vehicle from the top.

The design of the SU-85 continued to improve throughout the first quarter of 1944. The most noticeable changes were the shorter hand rails on the sides of the casemate that the SPG received no later than February of 1944. At the very least, the SU-85 with serial number 402221 on display in Warsaw already has these rails. Another noticeable change is the interlocking joint in the rear of the casemate. It was introduced in the 1st quarter of 1944. The pistol port in the right side changed its placement. New hinges for the panoramic sight hatch were added on February 20th, 1944. In March of 1944 the edges of the gun port were cut down and the pistol ports became bevelled.

The design of the gun mount bearing changed in January of 1944, and the turning mechanism carrier changed in February. In the 1st quarter the ability to adjust the gunner's seat vertically was introduced. Many complaints were made about the lack of this feature. The road wheel rims lost their ventilation openings towards the end of the summer of 1944. This was the last change to the design of the SU-85. Officially, the openings were cancelled by the end of April, but existing stocks meant that these rims still appeared. Factory #713, UZTM's road wheel supplier, only moved on to the new design in June of 1944.

The last change to the SU-85 was introduced around this time. After many complaints from the front lines the exhaust fan in the roof returned. Photos taken in the summer of 1944 show SU-85As with such a fan on the roof. This design was larger than the one on the SU-85-II, likely a large fan like on the IS-2 was used.

SU-85M belonging to Wojsko Polskie.

Work on modernization continued in parallel with production. The result of this work was the SU-100, the best Soviet SPG of this period. Stalin signed GKO decree #6131ss "On organization of production of SU-100 SPGs at the Uralmash factory and D-10S guns at factories #8 and #9" on July 3rd, 1944. According to this decree, production of the SU-100 had to start in September. However, it took time to ramp up production of the new vehicle and its gun, and so the SU-85A remained in production until November of 1944.

A hybrid entered production on September 1st, 1944. It was named SU-85M and essentially was a SU-100 with a D-5S85A gun. The installation of this gun into the new chassis had some problems, but it allowed the quota of 135 SPGs to be met. According to plan, 120 vehicles were delivered in October, and the last 60 SU-85M were built in November of 1944. After this, the factory fully switched to the SU-100.

In total, from August of 1943 to November of 1944 the UZTM factory produced 2650 SU-85, including 315 SU-85M.

Mixed success

The first SU-85 were issued in September of 1943. As it often happens with new vehicles, units began to complain about various defects. They were mostly linked to the D-5S-85 gun, but there were many others. The torsion bar of the driver's hatch broke often and had to be redesigned many times. There were also complaints about cracks in the armour, but not anywhere as many as the SU-122 caused. There were also engine and transmission defects. Complaints about insufficient ventilation resulted in experiments with two ventilation fans, but those were only approved on the SU-85M and SU-100.

Early SU-85 loaded on a train car, Sverdlovsk, fall 1943.

Officially, the SU-85 was designed to perform a wide spectrum of tasks, but it usually fought against enemy tanks. The first SU-85 SPG regiments were formed according to TO&E #010/483. According to it, the regiment was composed of 4 batteries of 4 SU-85s each. The regiment was also issued one T-34 tank as a commander's vehicle.

For instance, the 1435th SPG Regiment was formed in this way, the same one that started its career with SG-122 SPGs. This was one of the first regiments to receive the SU-85. By October 2nd, 1943, it was attached to the 68th Army. By 14:00 on October 2nd, the 1st battery of the 1435th regiment was in a defensive position at Klementyevo, subordinate to the commander of the 153rd Rifle Division. On the next day the Soviet forces began to cross the river Mereya at 11:30. Two SU-85s were supporting the offensive. The Germans opened fire at them. 1 was knocked out, and two of its crew were killed, two wounded. The other SU-85s in ambush opened fire at the enemy tanks and artillery that revealed themselves. The tank destroyers claimed a Tiger tank, but this was likely a different type of tank.

SU-85 on the front lines, late 1943.

A special commission was sent to the front lines to study the experience of using these vehicles. They included a representative of the Self Propelled Artillery Directorate of the GBTU, Engineer-Major P.N. Kuzin, an engineer from UZTM, B.B. Popkov, and the chief of tank production at the factory, L.M. Yarovinskiy. The objects of their study were the 69th Tank Regiment of the 8th Mechanized Corps and 1440th SPG Regiment of the 7th Mechanized Corps. The Tank Regiment was equipped with SU-85s according to TO&E #010/483, despite its name. When the commission arrived it had performed a 300 km march but not yet seen battle.

The 1440th regiment had already seen battle armed with the SU-122, having lost 6 SPGs irrecoverably and claimed 19 knocked out tanks, 15 burned up tanks, and 3 knocked out enemy SPGs. With their SU-85s, they had lost 5, claiming 18 enemy tanks, 6 of which were identified as Tigers. All surviving SU-85s had several hits to their front armour. Enemy shells formed dents up to 25 mm deep that were welded over. All losses were restricted to the initial period when the SPGs were used as tanks. After the SU-85 was used as instructed, the situation changed. As a rule, they would follow 200-300 meters behind the tanks. According to the crews, a Tiger's armour could be penetrated from the front at 600-800 meters and the side at 1200-1300 meters. The vehicle also turned out to be an effective infantry support measure.

Knocked out SU-85, early 1944. This was often the result when an attempt was made to use the SPG as a tank.

The SU-85 were rated highly by their crews. The precise gun, high maneuverability on par with the T-34, and high reliability were praised. However, by the fall of 1943 it was already remarked that the gun was not powerful enough. The gunners asked for a gun that could penetrate German tanks at 1500-2000 meters. This request was justified by trials against a Panther hull in late 1943, when it turned out that the shell could not penetrate the front. The crews also asked for thicker front armour. A proposal to revise the SPG regiment and increase the number of vehicles from 16 to 22 was made. The use of a T-34 as a commander's tank turned out to be a bad idea. The enemy figured out that this was a commander's tank and tried to knock it out first.

Soviet SPGs in Bucharest, late August 1944.

Despite the limited capability of the gun, the SU-85 was one of the Red Army's more effective SPGs. On November 22nd, 1943, in an ambush south of Yastrebnya, SU-85s commanded by Lt. V.S. Krysov and Jr.Lt. Makarov from the 1454th SPG regiment managed to repel an attack of 60 enemy tanks including 11 Tigers with help from an artillery battery. Krysov's crew knocked out 3 tanks and one more together with Makarov. A month later, on December 29th, 1943, Lieutenant V.A. Kurochkin excelled in the battle for Antopol-Boyarka. Kurochkin's opponents were two Tigers from the SS Leibstandart division. He managed to outmaneuver them and knock one out. Later Kurochkin will describe this battle in his story "War is War". The character of Maleshkin who was made famous in a movie of the same name is modelled after Kurochkin.

SU-85 with road wheels from a Panther.

There were many episodes like this in the SU-85's career. Yes, its gun could not always penetrate a Tiger or a Panther, but this did not prevent the tank destroyer from effectively fighting other tanks and SPGs. The Red Army finally received a medium tank destroyer that was closest to the German StuG 40 Ausf.G, but superior to it in nearly every way. The German assault gun had thicker armour, but it was presented at a flat angle.

Interestingly enough, during field repairs the SU-85 sometimes received road wheels from Panther tanks.

Considering the experience of the first battles, the commander's T-34 tanks were slowly replaced with SU-85 tank destroyers. Later, the TO&E #010/462 was introduced that increased the number of SPGs per battery to 5, and the total number per regiment to 21.

SU-85M in Berlin.

The SU-100 went into battle in early 1945 with a more powerful gun and thicker front armour, but the SU-85 remained the main Soviet SPG until the end of the war. These SPGs, including some SU-85M, ended up in the Wojsko Polskie. After the war, these SPGs remained in use alongside the SU-100. Most complete SU-85s that survived to this day can be seen in Poland. In addition to two surviving SU-85s, the museum in Poznan has the only surviving SU-85M. Today there are 11 SU-85s that survive in various conditions. The most interesting one can be seen in Tbilisi, as it is the only SU-85 produced in 1943 that survives to this day. The Central Museum of the Armed Forces in Moscow also has its own SU-85.


  1. Was the SU-85M has front-heavy as the SU-100 is reputed to have been, or did it fare better?

    1. The 100 mm gun was significantly heavier, so I imagine it was better balanced.