Útočna Houfnice 15 cm StuH 43 na podvozku ST-I

Third Czechoslovak Republic (1946)
Assault SPG – None built, blueprints only

Czechoslovak-made vehicles, such as the LT vzor 1938 light tank and the ST-I tank destroyer based on it (this is how they were called ‘at home’; in most of the world, they are better known under the German names Panzerkampfwagen 38 (t) and Jagdpanzer 38(t)) became some of the ‘bestsellers’ of their time. These served with the Third Reich, Sweden, Switzerland, Lithuania, Peru, Iran, and many other countries. But even back home, in Czechoslovakia, these vehicles were not deprived of attention. After the end of World War II, many modernization projects were developed on these chassis. One of these variants was called ‘Útočna Houfnice 15 cm StuH 43 na podvozku ST-I’ (eng. ‘Self-propelled Assault Howitzer 15 cm StuH 43 on the ST-I chassis’).

Known as German, but Born Czechoslovak

As the Second World War progressed, Germany needed more armored fighting vehicles that were cheaper and quicker to build. They started using hulls of captured tanks and reliable but obsolete tanks, such as the Panzer 38(t), to mount anti-tank guns and artillery howitzers. This resulted in the production of the Marder series, which carried powerful guns but had thin armor, an open-top fighting compartment, and a high profile which made them easy to spot on the battlefield.

The Jagdpanzer 38(t) tank hunter was designed to have a very low profile, which made it hard to target and easy to conceal. It was only 2.10 m (6 ft 10.6 inches) high, which was ideal for ambush tactics. It was armed with a powerful high velocity 75 mm Pak 39 L/48 gun that could knock out most enemy tanks. Moreover, it was cheaper and quicker to build than a Panzer IV, Panther or Tiger tank.

The Jagdpanzer 38 was not designed to be a close combat vehicle, used at the head of an attack, like a tank, but was intended to be deployed on the flanks to stop counter-attacks. A pack of Jagdpanzer 38(t) tank hunters would hide in a wood or thick hedgerow and pick off enemy tanks at long range.

Thanks to the great numbers of Jagdpanzer 38s built at the end of the war, it got to see service with a number of different armies during the war and after. The Czechoslovak Jagdpanzer 38(t) (several dozens were captured in and around Budapest in 1945) were designated ST-1, for ‘Stihac Tanku’ or ‘Tank Hunter’. 249 were pressed into service. Therefore, after the war, the Czechoslovaks had a sufficient number of Jagdpanzer 38(t) available to them. They produced 150 more and used them until at least the early 1960s.

Name of the vehicle

In the original documents, the vehicle is referred to as ‘Útočný vúz s 15 cm houfnicí StuH 43’, which can be translated as ‘Assault vehicle with a 15 cm howitzer StuH 43’. This is just a preliminary name of the vehicle. With further development, it would, like other projects from Czechoslovakia, have probably received a designation along the lines of ‘Útočná Houfnice 15 cm StuH 43 na podvozku ST-I’, which can be translated as ‘Assault Howitzer 15 cm StuH 43 on the ST-I chassis’.

Description of the Project

On November 4, 1946, Škoda presented a project at their factory, showing the installation of a 15 cm StuH 43 assault howitzer, produced during World War II for the needs of Nazi Germany, on the chassis of the ST-I. Alas, the insufficient traverse angle, the short firing range, the small stock of ammunition carried and other issues sealed the fate of the project. The proposal was rejected, and any development was discontinued.

Armament

The StuH 43 149 mm (5.9 in) howitzer was chosen as the main armament for this self-propelled gun. It had proven itself during the war. This howitzer was installed in the assault self-propelled gun Sturmpanzer IV, also popularly known as ‘Brummbär’. There were also plenty of various ‘paper’ projects, such as installing this gun in the turret of the Panzer V Panther medium tank.

In general, this howitzer, developed by Škoda, was one of the few large caliber guns of the World War II period mounted on an armored self-propelled chassis, from those built in metal and adopted by the army – along with the Soviet ML-20S from the SU-152. Even though it had a large caliber, the ÚH-ST-I would have had no problems with recoil – thanks to modernized gun trunnions, mantlet and ball mount. The recoil length of the howitzer was 560 mm.

It is worth mentioning that one of the most significant disadvantages of the vehicle were its horizontal and vertical aiming angles: 0° depression, +25° elevation, 3.5° traverse left and right. For comparison, even the Sturmpanzer IV, which was outdated by the end of the war, had far more adequate aiming angles: -5° depression, +30° elevation and 10° traverse to the right and left, which was already not enough in the years of its use. Another problem of the vehicle was the quantity of ammunition carried, which consisted of only 10 projectiles (3 were placed on each of the sides, 3 on the floor and one inside the howitzer). It is not surprising that all these drawbacks were major reasons for rejecting the project.

Armor

The armor of the ÚH-ST-I (StuH 43) remained similar to that of the ST-I: frontal armor of 60 mm, 20 mm sides, the roof of the combat and motor compartments at 8 mm each, 10 mm belly and 20 mm rear. Obviously, this would not have been enough for an assault vehicle performing combat actions on the front line in 1946. Even if the armor could withstand some standard 57-76 mm caliber guns, perhaps even some recoilless ones, opponents armed with guns of calibers from 85/90 mm and higher, which had been gradually adopted everywhere by that point, would penetrate this armor with ease.

On the other hand, one of the positive aspects of the vehicle’s survivability was its compact size and low (about 2 m) silhouette. Considered together with the well-angled armor plates, it probably had better survivability on the battlefield than any of its analogues of that time.

Running Gear and Propulsion

There were no plans to change the engine, suspension or transmission of the vehicle. Therefore, it retained all the “charms” of the ST-I: an overloaded frontal part (or, at least, working at the limit of the suspension) and a weak 12-cylinder Praga EPA AC petrol engine, with a capacity of 160 hp at 2,800 rpm.

Nevertheless, even in this regard, the vehicle had possible paths for modernization. Its internal volume already allowed the installation of a more powerful Tatra Typ 103 engine (220 hp), which would have significantly improved the driving performance of the machine. In addition, in theory, it would have been possible to transfer the gun mount to the chassis of the Jagdpanzer 38(d) – another ‘too-late-for-the-war’ project, but German. However, this is only speculation — there were no such plans in reality, and the Jagdpanzer 38(d) did not intersect with ÚH-ST-I in any way (even in terms of years of development).

Conclusion

The ​​Samohybná Útočna Houfnice 15 cm StuH 43 na podvozku ST-I was another project that was “too late for the last war, inadequate for the next”. If such a concept would have been proposed a couple of years earlier — not only would it have been implemented in metal, but it would have stood a good chance of taking part in combat actions. It could have been built in conditions of acute need, which the Third Reich had when it was ‘struggling in death convulsions.’ In the absence of it, there was no sense in this (and many others) conversion. And, soon, the context began to change — large-caliber assault vehicles, such as the ÚH-ST-I, Brümmbar, SU-122 and many others — gradually faded into the past, giving way to more and more universal combat units.

Útočná Houfnice 15 cm StuH 43 na podvozku ST-I specifications table
Dimensions (L-W-H)	Length: 6,270 mm Width: 2,630 mm Height: 2,100 mm
Crew	3 (commander, gunner, driver)
Armament	15 cm (149 mm, 5.9 in.) StuH 43
Ammunition	~10 rounds
Elevation Arc	0º…+25º
Horizontal Arc	3.5º both sides
Mass	~16 tonnes
Engine	Praga EPA AC petrol engine V12 (160 hp at 2800 rpm)
Top speed	40 km/h (25 mph)
Suspension	Surin-type, leaf springs
Hull Armor	Front upper – 60 mm @ 30º Front lower – 60 mm @ 50º Mantlet – 60-90 mm Sides Upper – 20 mm @ 50º Sides Lower – 20 mm @ 75º Sides Skirts – 5 mm @ 90º Rear – 20 mm @ 75º Casemate roof – 8 mm @ 0º Motor department roof – 8 mm @ 20º Belly – 10 mm @ 0º

Sources

• Blueprint Zb 16050-P, VHA Praha, FL: VTÚ 1946, KL: 5, SL: Čj. 8680 Taj.
• M. Dubánek, «Od bodáku po tryskáče: Nedokončené Československé zbrojní projekty 1945–1955.»
• Pablo Escobar’s gun parameters table;
• https://rotanazdar.cz/?p=9903&lang=cs;
• https://www.valka.cz/CZK-15cm-StuH-43-na-platforme-G-13-150mm-utocna-hufnica-t123392;