The battlegroup gun

This blog post will argue for a multi-purpose, relatively short-ranged "battlegroup gun".

Army artillery was historically divided into siege artillery, fortress artillery, field (battle) artillery and regimental (infantry) guns.

The distinction between field artillery (later divisional artillery) and regimental or infantry guns (later battalion mortars) was driven by a need for long-range main effort artillery that dominates the battlefield on behalf of the army (or Napoleonic-era corps, later division) commander and some artillery that supports an infantry regiment (later battalion) on behalf of the the regimental (later battalion) commander.

The latter was required to be more mobile (lightweight) to keep up with an infantry advance and being too short-ranged for a higher level main effort weapon was an advantage rather than disadvantage.

I wrote a lot about this before, but decided to revisit the topic:

/2015/12/battalion-battlegroup-organic-indirect.html

/2011/10/history-of-infantry-gun-in-us-and.html

The German army neglects the battalion indirect fire support. We have very few 120 mm mortars in active use. 155 mm howitzers (also not exactly many) cannot cover all indirect fires needs, though. They would often be 15+ km away, and radio communication may be unreliable over such distances. Their 155 mm shell is fine for long ranges, but rather inefficient for fragmentation effect since the removal of cluster munitions from the arsenal. The original reasoning for the 150...155 mm calibre was to penetrate field fortification overhead covers, and post-WW2 it was a quite efficient calibre for bomblet cargo shells. Nowadays its only really relevant lethal munition is the high explosive shell, which covers a rather small area with effective fragmentation effect relative to its weight. 155 mm is also rather inefficient for illumination munitions, and those are regaining importance since infrared illumination shells can nowadays assist the troops' night vision goggles in overcast and new moon nights. (IR-Illum may be unnecessary due to an alternative, though.)

Another advantage of an organic fire support is the shorter time of flight. Arms manufacturers can create nice presentations claiming that their gold-plated 155 mm round can provide fire support to dispersed troops in a 80+ km radius, but those rounds might be in flight for well over a minute while organic howitzers might deliver effect with cheap rounds with about 10 seconds time of flight and their dispersion would be so small that guidance would be superfluous.

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Now let's think about the land face of war: I suppose we could think of a corps area as a very shallow fish pond. The corps HQ may draw neat brigade icons on the map, but the fish tank would actually have much smaller fish than that; battalion battlegroups*, likely further divided into often independently manoeuvring company-sized battlegroups. Some fish would rest, a few would move, and sometimes there's a flurry of activity and suddenly all of them move for a short time and shoot for an even shorter time.

There would be no "front line". The corps commander would be well-advised to rather give frames to the manoeuvre forces; a line which opposing forces shall not pass and a line which friendly forces shall not pass without explicit (per-)mission by him. Orders might also be focused on points; reach this point by a certain time. (I'll lay out another command technique approach in a later blog post.) The manoeuvre forces would have arrangements for cooperation and if needed hierarchical decision-making (between commanders of formations or units of the same level), but most decisions would be made by leaders on the spot. 

There's something remarkable about mobile warfare, and such land warfare would be a mix of hiding/resting an rapid movements/clashes. You don't really need great firepower ranges when you're highly mobile. There's no advantage to having your artillery far from your spearhead if this doesn't add to security - and it would not with a mobile battlegroup. Instead, the artillery might be tasked to help secure the less line-of-sight combat-capable elements of the battlegroup (munition vehicles, fuel vehicles, bridgelayers, electronic warfare vehicles, air defence vehicles and so on). Additionally, you could simply move some 10 km towards some bridge or helicopter forward operating base if you wish to shell it and are 10 km too far away for it.

The one reason to give a battlegroup long-ranged (~40 km) artillery could be to enable a massing of fires from multiple battlegroups in one fires mission on one target. This could make sense, but I suppose it's needlessly troublesome. This burdens the mobile battlegroups with the munitions required to support other battlegroups and the battlegroup artillery piece becomes a much bigger and thirstier (likely tracked) vehicle. The fires would be tell-tale signs giving away the bivouac site or forcing the battlegroup to keep its own artillery outside of its bivouac (and thus less secure).

I suppose the superior approach is to divide the brigade into up to four battalion battlegroups and one support group. The support group would provide centralised services and an umbrella of support (electronic warfare, area air defence, long-range artillery fires). This allows for the desirable massed fires out to 40 km, or with exotic munitions out to 80 km from the brigade supply group. 

Meanwhile, the battalion battlegroups could mirror this with their own split; multiple company battlegroups and one battalion support group which would include much less ambitious support (bandaging, two days worth of supplies carried, short range air defences, <20 km range artillery fires).

A use of the 105 mm calibre allows for artillery fires from wheeled vehicles**, which are well-suited for rapid movements with little fuel consumption, little fatigue and few maintenance needs.

/2014/01/truck-mounted-artillery.html

(105 mm howitzer high explosive shells typically weigh 15 ...17 kg, 155 mm HE shells typically 42...44 kg. The difference in area covered with fragments is not nearly this great because fragments of a given useful size lose velocity rapidly. The greater quantity of fragments of a 155 mm HE shell can keep a good area density of fragments farther out, but it cannot magically sustain the energy of the identical fragments and their initial velocity is similar. Alternatively, it could go with fewer bigger fragments. The optimum design usually depends on what effect on impact is required. NATO prefers the 155 mm calibre mostly for more efficient use of personnel (a 155 mm gun requires about as much personnel as a 105 mm gun) and greater range. 150...155 m calibres were subjectively preferred over 105 mm during both world wars, but tables telling how many shells are needed for a given purpose (suppression or destruction) treat both calibres as substitutes and tend to show that you need less shell mass with 105 mm shells to do the job. Both 105 mm and 155 mm use the same one fuse per shell, and fuses add a substantial cost to the shell and explosive filler.)

The 105 mm calibre could effectively provide support with high explosive, multispectral smoke, (near-)infrared illumination and even a special fin-stabilized (slip ring***) mortar bomb for extremely close high angle fire missions (down to 400 m as 120 mm mortars can do, this requires 80° maximum elevation). They might also deliver precision guided munitions occasionally, particularly fin-stabilized ones with slip ring.

A 105 mm gun could even be used to launch guided subcalibre (such as naval 76 mm HE) projectiles at much higher velocities than the full calibre muzzle velocities, which in combination with 80° maximum elevation would offer an effective heavy anti air gun capability. This might be useful to destroy (or deter) at the very least flying observation drones without expending missiles that cost 1+ M € apiece on them.

Another option would be to use a 320° training ability of the turret (assuming a dead angle for low elevation shots caused by a hardened cab; so 360° training, but 40° not usable for lower register shots) for some auxiliary anti-armoured vehicles capability. Suddenly appearing armoured recce vehicles, IFVs and from some angles even MBTs could be defeated with tandem shaped charge (fin stabilized) rounds in fixed combustible shell cartridges.

This mirrors the multi-purpose potential of brigade-level artillery, especially the MRLs just as the battalion battlegroup-level support group mirrors the brigade-level support group.

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The objective that drove my reasoning might be obvious to the reader by now; the battlegroups should be as compact and agile and least be burdened with tasks as possible. They should thus be limited to line-of-sight combat troops and some essential support for the same, not with any further support tasks. We should leave as much of the fuel and munition carrying and consumption to the brigade support group.

The conventional answer would be to use 120 mm mortars, and I suppose that the much greater versatility of 105 mm SPGs with turret is obvious as an overwhelming advantage. Additionally the spin-stabilized 105 mm shell is just as deadly as a 120 mm mortar bomb, but has much less dispersion. Very flat shots out to maybe 2 km distance could normally be considered to have more dispersion in range than mortar shots, but electronic fusing based on counting the revolutions (the spin length being known, as it's defined by the barrel rifling) enables accurate fusing at a set distance. Very flat 105 mm shots would furthermore be much harder to detect for counter-mortar/counter-artillery radars than the always high angle mortar shots.****

So to summarize; I'm in favour of an army indirect fires triad:

• battalion-level 105 mm turret SPG (multi-purpose) under battalion BG CO command and only in emergencies supporting other BGs
  
• brigade-level 155 mm SPG (main effort firepower, low priority on multi-purpose) under brigade CO command and supporting beyond the brigade
  
• brigade-level variable calibre MRL (multi-purpose) under brigade CO command, but also some external fire missions (mostly area air defence)

That being said, the German army (Heer) doesn't pursue such an approach. Its MRL force is diminished, having a marginal quantity of munitions (PGMs) in storage only. Its mortar force is close to non-existence. Our brigades lack organic 155 mm SPG fire support. This may be considered acceptable as long as there's divisional 155 mm SPG pool that could be parcelled out, but we have too little of that as well. As of Spring 2021 we had a total of four artillery battalions (155 mm SPG and 227 mm MRL) for a total of eight brigades (counting the German-French brigade as well). That's three arty Bn for seven German-only brigades. It appears it's more important (to the bureaucracy and politicians) to have almost 11% of our military personnel in the medical branch. That doesn't sound inflated at all, right?

S O
defence_and_freedom@gmx.de

P.S.: In the end, a mere look at the organisation and quantity of indirect fire support in the army suffices to declare our army leadership catastrophically inept, if not suspicious of being compromised by the FSB. This problem dates back for many years (1) (2). 

Disclosure: I have a weak spot for solutions that are modest, if not austere. This may have influenced my reasoning.

*: Up to 1,000 troops and 100 motor vehicles, led by a major or lieutenant colonel.

**: I would rather prefer 8x8 offroad logistical trucks as basis than smaller vehicles, as this minimizes the convoy size and quantity of needed drivers. /2014/08/the-dragoon-problem-lingers-on.html

***: Avoiding that the munition gets much of a spin from the barrel rifling, as much spin  renders fin-stabilization impossible. Fin stabilization allows 80° maximum elevation for indirect fires and it allows for much simpler 2D course corrections.  

****:  Counter-mortar/counter-artillery radars typically scan the horizon to detect shells, rockets or mortar bombs as soon as possible, during their ascent. Hills, woodland and buildings can create a dead angle in which these radar beams would not detect the ammunitions in flight. Mortar bombs with their apparently very reflective metal fins furthermore create a stronger echo than howitzer shells.

Edit: I may have been a bit too harsh on the Bundeswehr regarding mortars here. There are 120 mm mortar carriers (refurbished, but very slow M113 version)  in light infantry and mountain infantry battalions and towed (by 4x4 car) mortars in airborne battalions. It's still a very badly neglected arm.

 

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