Modern Assault Gun Systems:- The Assault Gun-Mortar.
I've touched on the topic of Assault guns already in a few articles. This article covers them in more depth, particularly lightweight systems. Assault guns are basically AFVs used in an offensive role and equipped with a hull mounted direct fire gun. I've always assumed that the Assault gun was the result of the then unsolved technical difficulties of mounting a large gun on contemporary turrets. In fact the design was more deliberately planned:-
In 1935, Colonel Erich von Manstein proposed that Sturmartillerie units were to be formed and used for direct support of infantry divisions. They were to be equipped with assault guns mounted on tracked chassis. Used to accompany the infantry into the attack, the assault gun's main aim was to knock out pill-boxes, machine gun nests, anti-tank guns and other obstacles. On June 15 1936, the order was given to Daimler-Benz AG to develop and produce an armored infantry support vehicle mounting 75mm gun. The gun was to have a limited traverse of minimum 25 degrees in order to provide direct support up to 6 kilometres. The gun was to be mounted in a superstructure that provided full protection for the crew. The height of this vehicle was not to exceed the height of an average man.
A memorandum submitted in 1935 to General Beck, the Chief of General Staff, by Colonel Erich von Manstein, suggested to revive the concept of the infantry Begleitbatterien (escort batteries). He indicated the need for an armored self-propelled gun to work under infantry control, the tactical employment and the nature of the weapon itself: "Assault artillery fights as escort artillery within the framework of the infantry. It does not attack like the tank, does not break through, but carries the attack of the infantry forward by quickly eliminating the most dangerous objectives through direct fire. It does not fight in large numbers like the tank units, but is normally employed at platoon strength. The platoon, or even the individual gun, makes a surprise appearance in and then quickly vanishes before it can become a target for enemy artillery. The gun must be able to take enemy machinegun emplacements out of action with a few rounds. It must also be able to knock out enemy tanks; in comparison to them it has inferior armor, but a superior ability to observe and shoot first."
In combat the Assault gun proved to be a very effective system. The theoretical drawbacks of a turretless design never became practical problems. The basic concept was the same as that of the British Infantry Tanks, but since such vehicles were not classed as tanks, they were more likely to be under infantry control. To quote a Panzer Unit Bulletin:-
"...Light tank destroyer Jagdpanzer 38 proved itself in combat. Crews are proud of them (Hetzers) and they as well as the infantry have confidence in them. The most praised is the option of all-around fire from the machine gun. Great firepower, low profile and overall shape proved suitability to fullfil two main tasks: fighting enemy tanks and direct support of the infantry in defence and offense .".
The Germans established that the effective use of Assault Guns relied on observance of the following "rules"
Assault Guns always operated with Infanty.
The role of the Assault Gun was to support Attacks and Counter-Attacks. Missions such as pursuit and exploitation were to be left to tanks.
Assault Guns should be used en-mass rather than "penny-packet". Usual unit of maneuver was a company/battery of at least seven firing vehicles.
Assault Guns are a mobile system and should never be dug in. This did not preclude firing from behind cover whenever possible.
Assault guns proved to be a very effective system but it is apparent that today the only war fighting system in the west that can offer the same capability is the 70 ton MBT, which are expensive, difficult to transport and often in short supply. The Assault gun was not intended to replace the tank but for certain roles it did prove more effective. Correct use of a modern assault gun would enhance the capabilities of various units while freeing tanks for roles they are more suited for.
First let us consider the possible configuration of a potential modern Assault gun. For the most part the vehicle will be based on components of the M113 family, with possibly some parts from the M2/3 and M8. A gross weight of 15 tons is not impossible and this would make the system C-130 transportable, freeing C-17s to transport M1s and M8s. Our vehicle will have a rear engine and a well sloped, heavily armoured frontal aspect. Main weapon will be a 120mm gun-mortar. This will be mounted in the hull in such a way that it can still be fired at high elevations. On the roof is a remote controlled or one-man turret armed with a machine gun and 30mm cannon such as an ASP or M230. This will be referred to as the "Light Turret". The vehicle is also armed with a co-axial MG, smoke dischargers and firing ports.
All of the necessary parts for such a vehicle already exist.
Such a vehicle could easily be produced:-
Take an M113 and reverse all the gearing.
Slope the rear wall of the vehicle and up-armour it (this now becomes the front).
Install an "off the shelf" 120mm Gun mortar in the front plate of the vehicle, exactly as it would be installed in a turret.
Move the driver to a more useful position.
Fit a gunshield to the commander's MG, possibly replacing it with a 30mm ASP. Alternately install any one man turret such as an Amtrack turret with a .50 and a 40mm AGL or a turret with an ASP and co-axial MG.
For some idea what such a vehicle may look like, view:-
Note how compact these vehicles are in comparison to the accompanying infantry. Strictly speaking, the Hetzer is a tank destroyer, not an assault gun, but the difference is more one of application than form.
Roles for a Modern Assault Gun-Mortar.
Support of Infantry Offensives. This is the classic assault gun role, as described by Manstein and still very much needed. Being a smaller target and with a well defended frontal aspect Assault guns are far less vulnerable than tanks in this role. The use of Assault guns also allows tanks to be held in reserve for exploitation missions. As well as conventional mortar rounds, the Assault Gun-mortar will also make use of high capacity HE, HESH and HEAT ammunition. Russian experience has indicated the value of WP rounds for Urban operations, and these are already available as 120mm mortar rounds. As well as advancing with the infantry, the Gun-mortar has enough range to allow stand off direct fire support.
Support of Infantry Defense. In this role the vehicle is essentially a mobile pillbox. The low profile and small size of the Assault Gun-mortar means that it is easily hidden to assist in a positional defense. Assault Gun-mortars may have entrenching blades to improve the protection of their firing positions. Such guns can also be deployed behind ridge crests, appearing only to fire. In such a position the vision systems on the Light turret allow the crew to peek over the ridge. Canister or beehive loads may be useful in this role and the weapons of the Light turret will also be effective against infantry, helicopters and light vehicles.
Artillery and Mortar Missions. Designing the Assault Gun-mortar so that the main weapon can be used at a high elevation allows the vehicle to provide indirect fire when the tactical situation demands this. An Infantry Battalion's Assault guns are therefore both Armour and Artillery. Assault Gun-mortars built in the west will probably utilize a weapon such as RO Defence's Armoured Mortar System which has a range of 9.2 km and can use the same ammunition as the M120. The sheer variety of ammunition types available for the 120mm gun-mortar will probably necessitate a human loader. Possibly the breech could have a hopper to which rounds are easily added or removed to allow rapid bursts of fire. Indirect fire can be used to deliver guided top attack munitions.
Tank Destroyer. TOW equipped platoons should also field a couple of Assault gun-mortars. Roles include:- Close and medium range anti-tank fire. In this role a Rocket Assisted Stub-wing APFSDS round would be useful. Use of a rocket booster would increase the initial velocity to one comparable with Tank gun rounds. The gentler acceleration of this round may allow the use of a terminal guidance system. Support fire:- firing Illumination rounds to assist ATGW used at night. The Light Turret armament will be effective against light vehicles, conserving ATGWs. A multiple dart round for the main weapon would be effective in both a direct fire and a high angle role. The armament of the Assault gun-mortar will be highly effective against infantry attacks against the Anti-armour unit.
Reconnaissance. The light weight and high mobility of the Assault Gun-mortar makes it the ideal support system for scout units mounted on light vehicles such as the HMMWV and BV-206S.
Escort Duties. The main armament of the Assault Gun-mortar has a limited traverse but the short length of the vehicle and use of track propulsion allows the vehicle to slew rapidly to face a threat from the roadside. The large calibre of the main weapon gives it an effective canister round for anti-ambush fire and the high elevation capability allows direct fire in mountainous terrain or indirect bombardment.
Engineer. The Assault Gun-mortar would be a useful demolition gun system for combat engineer units. Being heavier than M113s it may also serve as the units dozer although the blade may be more useful mounted on the back. Thermobaric rounds for the 120mm mortar may have engineering applications such as minefield clearing. They also will prove useful as demolition and anti-personnel rounds. The hull mounted Gun-mortar may have another application. Sections of Bangalore torpedo can be inserted in the breech and fed down the barrel, allowing engineers to emplace mine clearing charges while under the protection of armour. The light turret can lay down suppressive fire while this is undertaken.
Variants. An Assault Gun-mortar could mount a flame-thrower system, much like the Churchill Crocodile, with the fuel held in a jettisonable trailer. Once the fuel is expended the vehicle can still operate as a conventional assault gun. Assault Gun-mortars can also mount ATGWs such as Hellfire to supplement their gun armament. Assault Gun-mortars could mount MBRL systems, much like the Sherman Calliope.
On a modern system the rockets would be loaded in pallets that can be jettisoned once fired. The armament could include a AGL, either mounted in the hull or on the light turret. This would be a useful offensive/smoke laying system loaded with 40mm WP grenades. Some variants might employ a 60mm under-armour mortar. The vehicle that I have mainly described in this article is a lightweight one equipped with a versatile 120mm gun-mortar system. Heavier vehicles are possible, as are other armament options. Most of the better known assault guns have been equipped with some from of tank or anti-tank gun. There have also been models equipped with heavy infantry guns or howitzers. The Russians have favoured vehicles mounting artillery guns such as the M-46 130mm and the 152mm. A ISU-152 type assault gun armed with a 155mm weapon such as the G5 would effectively fill the "ARtank" mission, and be particularly effective in desert conditions, providing both long range direct fire and indirect bombardment in support of tank formations.
The 152mm Gun-launcher would also be a useful system for light assault guns. Assault guns mounting short barrelled 105mm or 155mm howitzers are also possible. In other articles I've suggested the developement of a heavy infantry gun using the same ammunition as the 155mm mortar, and similar weapons have been used as assault guns. Vehicles mounting the 165mm Demolition gun would be useful to engineers and troops in MOUT missions. Another useful system would be the Assault Gun Support Vehicle. This resembles a IFV/APC but carries extra assault gun ammo rather than infantry. The AGSV also serves as a "wingman" for the Assault Gun, using its armament to suppress Anti-armour teams.
Acknowledgements. Many thanks to George Parada of the Achtung Panzer site and Ben Lindsey for allowing the use of the images used in this article.
The quote below is from "Inside the Soviet Army", by Viktor Suvorov. You can find it in the Part VI: Equipment, the chapter entitled "Secrets, Secrets, Secrets" (Pg. 243). I think this will help you understand why they are not commonly photographed or seen.
"The policy of observing the strictest rules of secrecy has completely justified itself. For this reason it is universally accepted and is applied with ever great rigor. As a result, officers serving in nuclear submarine may know, for instance, the output of the boat's reactor, if they are involved in its maintenance, but they will not know the maximum depth to which the boat can dive, since this does not concern them. Others may know its maximum depth, but will not know the range of the missiles which the submarine carries. This policy of secrecy is applied to the production of heavy assault guns, mounted on tank chassis. A tank with a fixed turret is an excellent weapon. True, its arc of fire is reduced, but against this, a more powerful gun can be installed, the quantity of ammunition it carries can be increased, it's armor can be strengthened without increasing its overall weight and, it is much easier to manufacture. (My Emphasis- PW) Guns of this sort are indispensable, when used in close conjunction with tanks with normal turrets. Both the Soviet and the German generals came to realize their value during the war, but since then only the former have continued to produce them. In order that other countries should not be tempted to introduce this simple but excellent weapon, all Soviet heavy assault guns are protected by strict security measures. Their production has continued, without a break, ever since the war. Every motor-rifle regiment (inside the USSR, but not abroad) has one battery of heavy assault guns. In the 1950s the powerful D-74 (122mm) was mounted on a T-54 tank chassis, then the M-46 gun (130mm) was installed on the T-62 tank chassis. All regiments, without exception, have heavy assault guns of this type. They are kept in mothballs for decades, never seeing the light of day. Their crews train on T-54 and T-62 tanks. Sometimes they are shown the gunsights of the assault guns. They know the tactics which will be used and they know how to service the engines. If war should break out their commander would disclose to them that instead of tanks they were about to be equipped with something which was similar but far more powerful and better armored. In the middle of the 1970s all these guns were replaced by more powerful models, but naturally, they were not melted down. Instead they were either sent to the Chinese frontier to be installed in concrete emplacements or sent to holding depots, in case they should come in useful one day."
UPDATE My thanks to Sven Ortman for drawing my attention to the following prototype built in the late 1970s/ early 1980s.
Weight of this system was 14 tons. I think the frontal armour needs to be a better shape and thicker to make this a true assault gun, but it is interesting that this configuration is possible without relocating the engine. I imagine that at the time nobody was interested in assault guns or an artillery system that could be transported by C-130. Nowadays such a vehicle could easily fill the role of IBCT Mobile Gun System if fitted with a suitable gun. It easily meets the size and weight requirements (unlike the LAV-MGS) and could carry a greater weight of protection. A 120mm mortar armed variant is also possible. One possible flaw I do see with this prototype was the lack of independent traverse for the main weapon. This would make it difficult to track moving targets such as vehicles. This particular configuration is probably best used as a indirect fire SPH with an auxillary direct fire capability.