2015/12/12

Battalion battlegroup organic indirect fire support

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In the post "An army corps for Germany" I preferred 105 mm guns over 120 mm mortars as battalion battlegroup-level organic indirect fire support:

"155 mm howitzers are not enough, though. Their range makes them a too high-level asset, only short-ranged fire support that's not available for helping at great distances will be reliable support. This is the case for organic, range-limited fire support. Mortars did meet this requirement for generations. Their issues in face of counter-mortar radars and long time of flight never really went away and the French rifled 120 mm mortars provide but a limited relief. Maybe it is about time to say goodbye to mortars and add a battalion battlegroup-level artillery support of organic artillery, akin to WW2-era infantry guns and 18th century Regimentsstücke.

This could take the shape of 105 mm soft recoil guns or high-low pressure guns, for example. The smaller calibre would make support with illumination rounds, pinpoint shots at identified positions and the like much more economical. At the same time, the limited range of less than 20 km would ensure the gun crew would rarely be expected to assist other units than the one it's moving with (155 mm L/2 artillery range is in excess of 30 km)."

The once excellent British FV 433 Abbott 105 mm SPG, based on the FV430 (APC-style) light tracked AFV family. It became obsolescent when 155 mm SPGs began to outrange it badly and received very effective cluster munitions. 105 mm SPGs are obsolete as field artillery, but is still much superior to 120 mm mortar carriers.


This time I'll offer a more detailed rationale for this. One reason is the demand for range, driven by low force densities as I call it.

"Low force density. Modern intra-European conflict can be expected to have low force densities in an early stage, and a quick decision should be sought (to avoid the greater damage of protracted conflict). Military theory should thus pay much (more) attention to the scenario intra-European conflict with a low forces/area ratio. This applies to the loss of the former functions of a front line, too."


Low force densities were observed up as a symptom in the Eastern Ukraine:
"A third trend, manifested uniquely only on the Russian side, is the centralization of artillery down to the level of maneuver battalions. Historically, since the end of the World War II most armies have placed their artillery fire support at the brigade (US and NATO) or regimental (USSR) levels. However, in the Donbas, the Russians are permanently assigning (not cross-attaching) artillery batteries to mechanized and tank battalion battle groups. As mentioned earlier, many of these systems are the self-propelled 2S1T Godzik 122 mm or towed D-30 gun-howitzer, which makes sense, given their dual direct/indirect fire role. However, there are many examples, where the Russians are providing either a self-propelled 2S3 Akatsiya or towed D-20 152 mm howitzer battery and/or BM-1 Grad MLRS. At first glance this appears to be an anomaly because the 18km range of the 152 mm artillery exceed the normal operating area of a maneuver battalion. But there is a unexpected rationale for this trend - it is necessitated by the abnormal dispersed nature of combat where the battalions are operating on a much broader front and thus the area typical of a Cold War brigade. The increased operating area of Russian maneuver battalion reflects both the condition and the imperative: the Donbas battlefield has a relatively low force-to-space ratio; and the increase lethality on it mandates wider dispersion for survivability."

source: DRAFT "Lessons Learned from the Russo-Ukrainian War" Dr. Philip A. Karber, 8 July 2015
All grammar disasters in the quote are explainable with the draft quality of the document.

Polish Land Forces 2S1 Gvozdika

related:
2011-08 The underrated genius gun  (D-30)

105 mm GIAT/Nexter LG-1Mk II

A typical Western 105 mm gun reaches up to 18.5 km out, with 15 km being a more relevant maximum range (with normal HE rounds without rocket assistance) and the shell has a similar weight as a 120 mm mortar bomb (both usually 15 +/- 2 kg with outliers). Some exotic mortar munitions aim at up to 16 km range, but the most high-powered 105 mm howitzer could go past 30 km range with exotic ammunition. In the end, 105 mm howitzers with ordinary HE munitions badly out-range 120 mm mortars with ordinary HE munitions.
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The study draft cited above also mentions the dual direct/indirect fire role (assault gun-like fire support from safe distances in case of the Russian 2S1) of 122 mm self-propelled guns (SPGs), and 105 mm is much better at this than 120 mm mortars (safe for turret mortars) as well (normal mortars can only fire at higher elevations than about 43°, and 120 mm calibre mortars usually have a minimum range of 400 m for this reason).  The same study mentions that the Ukrainians use the 2S1 as anti-tank vehicles with some success, and 105 mm calibre howitzers can indeed make use of 105 mm HEAT and HESH shells developed for tank cannons originally. 105 mm SPGs could thus self-defend against armoured reconnaissance vehicles and even add some security to support troops (since likely the SPGs will be somewhat distant from the tanks and infantry much of the time - just as the support troops).
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Typical 105 mm howitzer shells are also much higher than 120 mm mortar bombs (~490 m/s and 320 m/s) and unlike non-turreted mortars it can often be employed in the lower elevation group (below 43° angle) for a short time of flight. A 105 mm shell may thus easily arrive at the maximum range (about 6.4-9.5 km) of a 120 mm mortar bomb at about half the time (I lack the tables to exactly calculate this right now).
A short time of flight is of great interest in rapid responses to calls for assistance by troops in trouble and against moving or fleeting targets.
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I mentioned an increasing overlap of field artillery and air defence before, and 105 mm guns - particularly the extremely high muzzle velocity G7 "howitzer" from South Africa) would be usable as an air defence weapon against easy targets (drones; or more difficult targets with guided munitions) if installed in a turret (as SPG, the maximum elevation will not be less than 65°).
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120 mm mortars are in a dire state and a situation of neglect and resulting obsolescence in the Bundeswehr anyway, so switching to a different approach would be less inhibited by path dependency than if we had a prospering mortar arm.
 
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Fin-stabilised mortar bombs (spin-stabilised ones from rifled mortars are quite uncommon, but exist) are notorious for their susceptibility to counter-mortar radars. Such radars extrapolate the mortar position from the mortar bomb's trajectory. The shape of the mortar bomb (its fins) and the typically high angle firing (upper elevation group only) are the main culprits as far as I know, and both can be avoided with 105 mm howitzers. It would be possible to 105 mm howitzer users to avoid detection by radars at times
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Mortars used to be cheap and simple, easily mass-produced even during wartime. This is a thing of the past now, since such simple mortars are too easily hit by counter-fire. Even adding a mere 4x4 car for towing (instead of a horse in WW2 style) adds substantially to its costs, and at the upper end we see the 120 mm Twin mortar turret called "AMOS" costing more than a million EUR, installed on armoured vehicles costing about two million apiece themselves. 120 mm mortars are now either obsolete or expensive - just as 105 mm howitzers, and thus not substantially superior in regard to costs any more.
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Specialised munitions such as illumination, IR illumination, smoke and multi-spectral smoke shells are available for 105 mm howitzers, so it's possible to substitute for 120 mm mortars in this regard.
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MRSI (Multiple rounds simultaneous impact) is a howitzer capability. This style of shooting a howitzer allows for several shots fired in quick succession with different elevation and propellant charge sizes, with shells arriving almost at the same time (within few seconds) at the target. The idea is to surprise the target and hit it with multiple munitions before it adapted by moving out of the targeted area, closing hatches or seeking cover.
Mortars are nowhere as good at it, and admittedly, 105 mm howitzers with their modest range (in comparison to modern 155  mm howitzers) are not very good at it either, but still better than the mortars. The mortars crews' approach to achieve the surprise effect is rather to exploit the high rate of fire with constant ballistic settings, but mortars suffer from another problem with surprise: The subsonic mortar bombs announce their arrival with sound, whereas howitzer shells stay supersonic out to useful ranges. The howitzer thus adds one or two seconds to the duration of surprise.
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There are disadvantages of 105 mm howitzers compared with 120 mm mortars as well, albeit of limited relevance: 120 mm mortars are better at manual burst fire. Both 105 mm howitzers and 120 mm mortars have low sustained rates of fire due to thermal issues, but the 120 mm mortar's simple dropping of mortar bombs into the muzzle is quicker (up to 16 rpm with best-trained crews) than for 105 mm field howitzers (up to 12 rpm).
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Another drawback is that 120 mm mortars commonly shoot at up to 80° angle, whereas howitzers at up to 70°. I understand this is because of issues with the spin-stabilised shell's dispersion at higher elevations. The difference in elevation leads to restrictions regarding reverse slope engagements and generally the reachability of advantageous angles of descent (for best fragmentation effect of HE shells). This is a small firepower disadvantage of howitzers in these niches (not very relevant in the Eastern European flatlands).
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Finally, the howitzer itself that gets built into a vehicle tends to be somewhat more expensive than a mortar, making the whole system a few per cent more costly.
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The use of 120 mm mortars as battalion-level indirect fire support was the best choice during WW2, became questionable during the 1970's when the Warsaw Pact introduced its first own counter-mortar radars in quantity (SNAR-10 "Big Fred") and has become unsatisfactory during the 1990's when shrinking armies led to lower force densities and thus a greater importance of range.

I favour a 105 mm SPG based on a protected vehicle family (same as APC etc.) with a turret and a 105 mm gun-howitzer capable of somewhat higher muzzle velocities than the lightweight 105 mm pieces have (for a range of about 20 km with normal base bleed shells and for better effective range in direct fire defence). That would be the mixed battalion battlegroup's organic indirect fire support, its most responsive fire support for smoke, illumination and engaging small targets. Meanwhile, brigade and corps artillery with 155 mm SPGs and multi-calibre MRLs can specialise on Schwerpunkt indirect fires, counter-fires against artillery, cooperative engagements with air power and generally longer-ranged strikes.

related:
2008-07 Mortars and howitzers
2008-11 Cluster munitions ban
2011-10 A history of the infantry gun in the U.S. (and elsewhere)
2013-11 Mortar bombs and countermeasures
2014-01 Truck-mounted artillery
"Why Organic Fires?" Col R.F.Barry II

S O
defence_and_freedom@gmx.de

edit 2015-12-22:
I think I didn't clarify one important issue: 120 mm mortars can engage targets with a minimum range of 400 m, while 105 mm howitzers with 70° maximum elevation can do so at minimum indirect fire range (as usually defined for Western guns) of 2,500 m (using drag rings on the shell nose and minimum charge). 105 mm guns can engage targets below 2,500 m in direct fire mode, though. So there's a gap in indirect fire capability between 400 and 2,500 m in favour of the 120 mm mortar, which can only be addressed by having 105 mm firing units spaced at all times (a doctrinal remedy). This creates security effort challenges, of course - unless you intend to have some 105 mm SPGs with the combat troops and 4+ km away other 105 mm SPGs (along with your more safely positioned support troops) anyway. Even then there's still the disadvantage that you'd need a 2+ km long radio link (capable of text messages at least) in order to engage targets in defilade less than 2,500 m away from combat troops (while 120 mm self-propelled mortars with the combat troops could in theory open fire on basis of shouted commands). A "rear" position is common for mortar troops as well, though.
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7 comments:

  1. Interesting study draft about Russo-Ukranian war: UAVs to acquire targets and massed artillery fire to destroy them.

    I think you are right and range is a critical factor in artillery. For that reason I think the 155 mm is the way to go. More range and more explosive than a 105 mm. But I agree that 155mm howitzers are not enough and something is needed for short-ranged fire support.

    But I prefer a 120 mm mortar to a 105 mm howitzer because:
    1) Possibility to use guide ammunition.
    2) More explosive in a shell and better rate of fire than howitzer = better massed artillery fire.
    3) Softer recoil, so wheeled vehicles (better strategic mobility) can be used.
    4) A 8x8 vehicle with a turreted mortar, although expensive, could provide direct or indirect fire support with a 360º traverse, and very good shoot and scoot capabilities.
    5) High elevation main gun can be combined with an autocannon to engage low-flying UAVs/helicopters, something like the BMP-3 turret.

    Or perhaps the solution could be something like the russian 2S34 Hosta, combining a 120 howitzer or mortar to replace 2S1T Godzik.

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    1. 1) Guided and dispersion-reducing munitions (SPACIDO) are available for 105 mm, also laser-guided missiles. There were about 50 120 mm PGM projects, but hardly any 120 mm PGM production.
      2) 120 mm HE bombs have little over 2 kg HE filler, almost exactly the same as with 105 mm HE.
      3) 120 mm mortars have a worse recoil than 105 mm howitzers for a given shell impulse (shot mass * muzzle velocity) because howitzers have a (longer) recoil length and muzzle brakes. Soft recoil 105 mm howitzers can even be used on light lorries.
      4) So could such a vehicle with 105 mm howitzer, and would be better in direct fire and longer-ranged in indirect fire.
      6) 105 mm SPH would need no autocannon for the same purpose and tehre's no 120 mm mortar+autocannon combo anywhere.

      105 mm shells have a smaller dispersion than 120 mm mortar shells (and reach farther than them).


      The approach of using a RPV with datalink to scout targets for indirect fire is nothing special; the German army uses KZO for this purpose. https://en.wikipedia.org/wiki/Rheinmetall_KZO

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  2. I would still prefer the Draco, as it would provide better anti air protection and direct fire capability at the cost of artillery power. The range is about the same and it can fire more rounds to saturate the enemy C-Ram defense if needed.

    Supplemented with a close range MRLS platoon in the heavy company (TOS like) and LR ATGM platoon it would provide the battalion with enough indirect fire capability.

    SP mortars could still be used in the maneuver companies. 2 per company ala Stryker Brigade seem to work well.

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  3. This is a fascinating post, and the paper from Dr Kaber is particularly interesting.

    I remain unconvinced by the argument for a 105mm system; simply replacing mortars with self propelled howitzers deserves more attention to weight of fire, effects, and logistics implications.

    The Russian 2S1 and its derivatives appears to be a better all around system than the 105mm gun-howitzer, while retaining excellent mobility. The system is in service with a number of "western" nations, and delivers 50% more shell weight and 50% more HE filler than the 105mm and still manages a reasonable ROF.

    GAB

    GAB

    ReplyDelete
    Replies
    1. 50% bigger shells ~ 33% less shells per supply lorry.

      Seriously, I have yet to see anyone complaining that 120 mm mortars lack punch, and 105 mm howitzers have the same punch. 105 mm HE is ceteris paribus also more efficient in terms of lethal area/ammunition mass and bulk than 122 mm HE.

      This looks like the usual dissatisfaction voiced against reform proposals because they don't achieve perfection, but merely a significant improvement.

      It's not like I could through my writing introduce 105 mm as battalion indirect fire support, but more generally the dream of "perfection" is the arch-enemy of any "improvement".

      The quantities of 122 mm pieces and their ammunition in NATO may suffice for Poland, Hungary, Bulgaria and Romania (though most shells no doubt are very old), but it's no option of Germany, UK, France, US, Italy, Spain ... and 105 mm is a NATO standard already.

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  4. A 50% heavier shell does automatically mean fewer shells can be carried (apart from aircraft) - the 2S1 carries 40 rounds, the same as an FV433.

    The 105mm howitzer did not become a NATO standard on the basis of its technical merits and those technical merits have long relegated the weapons to niche artillery for light infantry – even there it has been challenged by heavy mortars. The 2A18 and 2S1 remain effective based upon merit.

    The SP versions of the 105mm have gone the way of the dinosaur for good reason. The FV433 falls far short compared to the 2S1, both have similar weight, ROF and ammunition storage, but the 2S1 has a much higher muzzle velocity (~680 m/s, some higher) making it far more effective than the 105mm howitzer against moving targets (to include tanks at close range), and fortified or masonry structures.

    The 105mm howitzer does not have the same “punch” as a 120mm mortar round – it is a different beast and has different weight of fire calculations. It is not sufficient to compare projectile weight and HE filler as effectiveness also is affected by the number, mass, and velocity of the splinters produced. If suppression against personnel and lightly armored vehicles is the desired capability, the 81mm mortar is arguably the most efficient munition in terms of weight of fire and logistics efficiency.

    GAB

    ReplyDelete
    Replies
    1. 105 mm became NATO standard because it was a proven calibre, and suitable for mountain gun use. The 122 mm guns are quite short-ranged for general artillery purposes and obsolescent as such in face of 155 mm L/52.

      "fortified or masonry structures" would be defeated by chemical energy (HESH shell), not by a high muzzle velocity. 550 mps is fast enough to deal with tanks at least out to 700 m, a useful AT self-defence range.

      Shell-embedded tungsten spheres are produce the best HE frag pattern, and that kind of ammunition is available for both 105 mm and 120 mm. 120 mm has an advantage at short ranges only because of a better choice of angle of descent. A special fin-stabilised 105 mm short range HE round fired from a 80° elevation turret could fix that.

      With equal shell technology, fuse technology and angle of descent 105 mm and 122 mm frag area will be very similar (much less different than shell weights).

      I consider having two different organic indirect fire support weapons (= an additional medium mortar) as logistically and fiscally inefficient.

      Forget about 2S1. It's a stretch to imagine NATO armies to re-introduce 105 mm SPGs even only as replacement for weaker 120 mm mortars, but it's outright unrealistic to expect the old NATO countries to adopt some Warsaw Pact relic like 2S1. They would rather develop an all-new rifled 120 mm gun than adopting 122 mm.

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