Divisional artillery

[archibaldthe1]

I looked through several US artillery manuals and compiled a summary, which could be useful for people to gauge how well the arty is modeled in the game (and what large undertaking it could be!) It goes without saying, but given I am not a specialist in the topic, I will definitely be misinterpreting things. And I am still fuzzy on quite a few aspect, but I doubt I'll figure them out anyway :)

Let me know if there are some other aspect of the artillery I should look up. I picked what I thought was relevant for the game, but that’s not exhaustive by any means.

@Toni was going to do some research on Wehrmacht, so it'll be interesting to compare what's similar and what's different.

Also, if someone knows or has these, I'd love if you could share. US archives have these, but due to covid you can't order copies.
FM 6-101 Tactics and Technique, Battalion and Battery, Motorized
FM 6-105 Armored Division, Artillery

[archibaldthe1]

Typical assignment:
105mm FA Bn directly supports Inf Regiment
155mm FA Bn is either in general support or reinforces fires of 105mm, the liaison is established between the two artillery battalions

From this assignment example, https://imgur.com/77bYvbv , we see that 7th FA Bn and 32nd FA Bn are in direct support of 16th IR and 18th IR respectively. 33rd FA Bn is attached to 26th Regimental Combat Team (CT indicates that the reinforced regiment has a mission that’s independent from the rest of the division). 17th FA and 5th FA are reinforcing 7th FA Bn and 32nd FA Bn fires, which means FO’s of 33rd FA Bn call in missions for 7th FA Bn should that be necessary. Finally, A/36th FA is a long-range Long Tom arty battery and has its own special mission (i.e. counterbattery fire or reinforcing others by the order of Div Arty)

Each artillery Bn has multiple forward observers embedded with the supported regiment, and those observers are not battery-specific, their mission is to report targets and adjust, the mission assignment is Div Arty function.

Originally posted by FM 6-20:

It is desirable to send out forward observers in the ratio of one to each front-line company or similar unit.

In addition to forward observers, batteries and artillery battalions establish their own observation posts. Division artillery includes organic air observation. Target (and subsequent fire adjustment) could come from any of these means of observation or from the liaison officer. Supported units could submit targets/support requests to the closest artillery party (here is a memo from 1st ID: https://imgur.com/FiXALgA )
Preplanned fires may be prearranged as to location and time of firing, for example, as part of a preparation; or they may be prearranged as to location only and then fired on call, for example, as a normal barrage.

Originally posted by FM 6-20:

Schedule fires are planned in independent series to avoid tying the attack to a time schedule over a long period. Each series corresponds to a maneuver phase terminated by the capture of an objective. Execution of a new series of fires is usually begun on call

Preplanned fires are split into concentrations and barrages. Concentrations are represented by circles of 100 yards increments in diameter. There are some very basic (depending on gun caliber) rules of how much fire is required to cover these: https://imgur.com/SkYewlj
I’ll talk about most of these parameters later, but want to clarify one point now: this table has extra range added to the concentration size (either 50 or 100 yards) - based on whether firing data are prepared from transfers of fire or map data corrected. In my admittedly limited understanding the difference is: Transfers of fire are prepared whenever registration can be effected (so the fire is more precise). The table in the document has it incorrect - the “safety error” for transfers should be 50 and 100 for map data corrected:

Originally posted by FM 6-40:

To insure enclosing the target in the concentration area, considering possible errors in the corrected data, the depth of each area is increased by adding a definite amount; to the near and far limits. This amount is called a range safety factor; for a transfer of fire it is 50 yards , for map data corrected it is 100 yards

Barrages are pre-arranges fire placed on a line.

Originally posted by FM 6-20:

Normal barrage placed on a critical area that cannot be covered effectively by the weapons of the supported troops. A battery has only one normal barrage. It is laid on its normal barrage when not otherwise engaged, and fires the barrage on signal or call from the supported unit

These are the type of fires available upon a signal. The rate of fire is a maximum at first, to build up a dense barrier of fire. After several minutes the rate is reduced to one that can be continued without undue heating of the pieces.
Emergency barrages are “secondary” barrages (could be arranged to re-inforce another unit’s normal barrage)
Rolling (everyone’s favorite :)) barrage is delivered on one or more successive lines, advancing according to a prearranged schedule. Lines are usually 100 yards apart. Rolling barrages normally do not use adjustments
Barrage width was also regulated by caliber https://imgur.com/amZuQ9Q The barrage lines are placed from 200 to 400 yards (at least eight probable errors) in front of the line occupied by friendly troops.

EFFECT SOUGHT.

Originally posted by FM 6-20:

Artillery fire may be for neutralization, destruction, registration, harassing, or interdiction effect.
a. Neutralization. Fire delivered on areas to destroy the combat efficiency of enemy personnel by causing severe losses and interrupting movement or action. Neutralization is established by delivering surprise fire in intense masses. It is maintained by intermittent bursts of fire in lesser amounts.
b. Destruction. Fire delivered for the sole purpose of destroying material objects. It requires, except when direct laying is used, a great deal of ammunition and time. Observation is essential. For the destruction of most targets, medium and heavy artillery are better suited than is light artillery. Fire is generally by one gun. 5 c. Registration. Fire delivered to obtain corrections for increasing the accuracy of subsequent fires.
d. Harassing. Fire delivered during relatively quiet periods, to lower enemy combat efficiency by keeping his troops unnecessarily alerted. Fire may be by single piece, platoon, or battery; the fire is intermittent. All echelons of artillery may fire harassing fire.
e. Interdiction. Fire delivered on points or areas to prevent the enemy from using them. Characteristic targets are roads used for moving supplies or reserves, crossroads, assembly areas, railroad stations, detraining points, defiles, bridges, and fords

Precision vs Bracketed fire

Originally posted by FM 6-40:

The primary object of precision fire is to destroy the target. It consists of a precision adjustment to place the center of impact on the target, and precision fire for effect. Precision methods may be used for an accurate registration.
The object of bracket fire is to inclose the target in a suitable bracket and then to cover the bracket thoroughly with fire. The fire consists of a bracket adjustment and zone fire for effect.

The adjustment procedures and even the fire for effect are quite involved in both types, so I’ll skip it with the exception of mentioning that with precision fire for effect, guns fire in small batches (6 rounds) and the fire is adjusted
There are different recommendation as to the size of the desired bracket for different target types. It’s again very rough, and depends on caliber
https://imgur.com/lKwdos9

Each caliber is assumed to have an effective burst radius that’s used to figure out how much lengthwise and widthwise the battery can cover:
https://imgur.com/Nm4Tbmj

If you go back to the concentration tables, the number of ranges and the number of sweep rounds (which I’m about to describe) are based on these burst values.
Now this caused a lot of back-and-fourth in the arty topic - the gap between guns’ fire does not seem right.

Originally posted by FM 6-40:

(3) An open sheaf is one effectively covering a maximum of front without sweeping. (4) A converged sheaf is one in which the planes of fire are converged at the points of burst. (5) A crossed sheaf is one in which the planes of fire converge at a point short of the points of burst, the bursts appearing in reverse positions from the pieces firing

There are different types of sweeping, but I’ll skip those too. You will notice that in the recommended target engagement https://imgur.com/lKwdos9 open sheaf is used unless the targets are stationary (I think that’s because the battery can get to open sheaf faster) Sweeping is used on pre-arranged fires though (both concentrations and barrages).
The manual states that in some cases (when sweep is not to be used), fire is shifted instead. I didn’t not find what exactly causes this situation, except that it’s undesirable if each gun has to cover a wide area during sweeping.

Salvo vs Volley fire: the first is each gun fires in sequence with a given delay, the second means each guns fires the prescribed number of shells as fast as possible.

Unobserved accurate fire requires surveys:

Originally posted by FM 6-100:

Commanders must allow for the time required for survey if support by accurate unobserved fires is expected. Some survey work may be accomplished at night but certain reconnaissance and topographic opera-tions have to be performed during daylight hours. The time required to complete survey operations in a division ar-tillery survey is so dependent on the type of chart available and the terrain involved that average figures cannot be stated. However, as a guide, the minimum time allowed for survey in planning an operation should be 6 hours of daylight.

Edit (Jan 9):
important feature of div arty in US was fire direction center, which provided gunnery solutions to all batteries in the battalion (in WW1, this task was left to the battery commander). In this article, we have some basic descriptions of the capabilities: https://apps.dtic.mil/sti/pdfs/AD1038889.pdf

Originally posted by Maneuvering to Mass Fires:

...
Calls for fire would now come directly to the battalion FDC from the observer, which computed the firing data, removing one link in the call for fire architecture.
...
One observer could now adjust the fires of an entire battalion, without relying on battery commanders

Explains how they were able to do without battery-specific forward observers.

There was an FDC one level above, that would enable mass fires of the entire division:

Originally posted by Maneuvering to Mass Fires:

Division FDCs replicated the technique, allowing for the massing of multiple battalions.
This allowed for the conduct of tactical fire direction at the division, which entailed the prioritization of targets in accordance to battlefield realities and needs. This allowed the division to determine which targets required the massed fires of several battalions.

[archibaldthe1]

How was the regimental artillery different in US Army? Cannon company was the organic regiment-level artillery in infantry division. At the time of Tunisian campaign those companies started with self-propelled 3x75 and 1x105 platoons. By the time the regulation FM 7-37 was written, the armament was 3x105 short-barrel howitzer platoons (motorized and easily movable, so similar employment principles)

Originally posted by FM 7-37:

The cannon company is characterized by tactical mobility and flexibility of fires.

There is no fire direction center:

Originally posted by FM 7-37:

The detailed fire control connected with the preparation and actual delivery of fire on a target is ordinarily exercised by platoon leaders or chiefs of section.

One thing to note, these cannons are expected to displace frequently and readily (perhaps not in the sense of the game's tactical battles, but more so over the particular engagement, as battalions or even companies move).

Originally posted by FM 7-37:

Frequently, he (Regimental CO) will direct that each cannon platoon support a designated infantry unit. Exceptionally, he may direct that one or more cannon platoons be attached to an infantry unit or to an attached artillery unit

The fires are delivered either on call or on the initiative of platoon or section observers. Now, this is not that much different from how either Bn or Div arty works - any observer, be it the supported unit, forward observer or the gun's/battery observation post can submit a target. The difference is in who makes the decision to satisfy the request.

Originally posted by FM 7-37:

Exceptionally, units of the cannon company may engage area-type targets; however, artillery is usually employed against such targets, while cannon company elements are employed principally against point targets. Appropriate targets for the howitzers of the cannon company are automatic weapons, antitank guns, mortars, infantry howitzers, troop concentrations, road blocks, pillboxes, strongly fortified buildings, and armored vehicles.
Exceptionally, the company may be employed to supplement the antimechanized defense of the regiment or other supported unit.

In this regard, scheduled fires weren't favored, unlike pre-arranged (in defence)

Originally posted by FM 7-37:

the platoons must be prepared to deliver concentrations of fire, on call, from prepared data on predetermined localities.
...
Exceptionally, the cannon company may be assigned the mission of supplementing artillery preparatory fires. Determining factors which may justify such a mission are:
(1) An existing deficiency in artillery support.
(2) The ability of the cannon company to provide its normal close supporting fires to the attacking battalion(s) at the proper time.
(3) The availability of an extra supply of ammunition at the positions from which the preparatory fires are to be delivered, thus insuring to the platoons their full organic supply of ammunition for the subsequent accomplishment of their normal missions.

Speaking of zones:

Originally posted by FM 7-37:

A platoon may be directed to provide close support to a particular unit of the regiment. In this case, it is not usually assigned a sector of fire or target areas. However, if two platoons are assigned the mission of furnishing close support to the same unit, the company commander will ordinarily fix the responsibility of each platoon.
c. One or more platoons may be directed to support the action of the regiment as a whole. In such cases the company commander usually designates the unit of the regiment or the sector of fire (or target area) which will receive priority in supporting fires. The company commander may change this priority as the situation changes, or he may from time to time designate specific targets to be engaged.

When possible, the cannons were instructed to fire registration.

[archibaldthe1]

I found Red Army equivalent to FM 6-40: Наставление артиллерии Красной Армии. Правила стрельбы наземной артиллерии (A guide for artillery of Red Army. Firing rules for field artillery)

https://drive.google.com/file/d/1X6dnh-YwfuLhM2WyJk8bSrxbkVahfECA/view?usp=sharing

As well as this Артиллерия. Вооружение и боевая cлужба (Artillery: Equipment and methods) https://cloud.mail.ru/public/CS6u/nRXTtkDXN (this one has characteristics of soviet guns of the period)

Neither unfortunately speaks to command and control (i.e. the organization of forward observers. liaison officers, etc), but it does largely have same concepts as 6-40 with some specifics as far calibers used and something exotic to US (say incendiary).
I'll use this post to add interesting details, since not everyone would be able to read in Russian :)

As you might have surmised from the game, RKKA was pretty active in using division and regimental guns in anti-tank role. A good section is dedicated to anti-tank fire. They also include regimental and even Bn weapons into the pre-arranged fires (at least they provide regulation on how much those assets can cover).

Pre-arranged concentration fire has interesting detail. Unlike what I saw in US regulation, Soviet one is prescribing multiple "intensive bombardments" with "methodical fire" in between: https://imgur.com/gxzGu7k, https://imgur.com/gFLxNjS
The regulation talks about neutralization effect on covered/uncoveed and observed personnel.
Unobserved 100x100 area containing personnel in cover calls for 2-5 intensive fires, 25-35 minutes overall. This ends up being extravagant 300 shells for 76mm, 250 for 107mm, 200 for 122mm and 120 for 125mm weapons respectively. 120mm mortars for this purposes are considered to have similar effect to 122mm Howitzers (they apparently generate fragmentation field twice of the howitzer's, but the latter generates heavier fragments). 82mm mortars ara "matched" to 76mm guns
Same condition, but uncovered personnel: up to 3 intense fires, 3-5 minutes each, with methodical fire in between. Ends up with much cheaper 75, 45, 24 and 18 shells respectively
Vertical step to cover the area in depth is 50 meters (i.e. 3 "jumps" for 100m). Sweeping is applied when the area is >1.5 times wider than open sheaf.
Observed uncovered: 76mm - 30, 122mm - 20, 152mm - 15
Observed covered (per 10m of trenches): 76mm - 60, 122mm - 40, 152mm - 30

Standing barrage (including "normal", which becomes the batteries' first priority) is same as US: https://imgur.com/mjBZJ9q
Columns in the first table are Caliber || Width in meters || Ammo expenditure
Noting that there is minimal safe distance and that 82mm mortars get 60m instead of 100
Interdiction - depending on whether observed or not. For observed, use the neutralize fires, unobserved - volley fire of the battalion 2-3 per gun, then methodical fire.

Here is an interesting one https://imgur.com/ly7PO0v (and you should see how quickly the shells are spent, so you'd better only target very important things!): after adjustment, the average requirement for "reliable suppression" of uncovered prone infantry at up to 4km distance is 76mm - 30-35 HE, 20-25 Shr; 122mm - 20-25, 152mm - 12-18.
Maybe this is not so suprising considering this basic chart Brits used (The following estimates the relative risks of becoming a casualty to ground-burst shells on ‘average’ ground)
Standing: 1, Lying: 1/3, Firing from open fire trenches: 1/15 – 1/50, Crouching in open fire trenches: 1/25 – 1/100

[archibaldthe1]

And just like that, I found the 2nd part of RKKA Artillery Regulation, so I can post some details on C&C (the document is from 1937, so things may have changed by the start of the war).
This site has the pdf:
http://ocher.biblioteka-perm.ru/informacionnyje_resursy/elektronnaja_biblioteka/obshhestvenno-politicheskije_i_istoricheskije_dokumenty/?page=3

"БОЕВОЙ УСТАВ АРТИЛЛЕРИИ РККА ЧАСТЬ 2"

Organizationally (and I am sure you saw that in some of the game’s operation) there is "Artillery of the army" and "Artillery of High Command Reserve", the former being organic arty up to Corps level and the latter is separate (often added to beef up organic support). Given how corps were done away with at the beginning of the war, I won't have any examples.

Same attachment vs direct support concept (the regulations calls the attachments "decentralized control". Particularly for regimental artillery, it is allowed to attach individual Regimental arty guns to infantry companies.
For battle missions, artillery may form support , long-range and demolition groups. For our purposes, support is relevant - that is formed from divisional arty and aforementioned AHCR. Each group support a regiment. Further down the line, artillery battalions (it's confusingly called "Дивизион" in Russian, which sounds similar to "дивизия") are supporting battalions, batteries are supporting companies. Regimental artillery could be attached on an individual gun basis to companies. Each battery gets assigned main direction of fire and secondary sectors (with the note that those secondary second complicate things a lot). Regimental artillery could take on the role of support group if one isn't formed from division arty.

We seem to get a liaison/FO section that is assigned to the supported unit, but while they are adjusting fire (which isn't even their primary mission), they do not seem to call in missions (only the unit commander can). Very interesting provision (if I am correct of course). Artillery is in change of establishing the connection. Battalion technically could get an air observer, but that's mostly for long-range artillery group. Each battery is supposed to organize its own observation position, and the fire adjustments could be done from there.

Tanks support is interesting. It could be provided via moving barrage with tanks signalling (radio signal, air observer, flares, flags) to lift and move the barrage. Or a via a sequence of concentrations (either on areas of suspected AT or at a line with the purpose to blind AT). Similarly, a signal is sent to move to the next concentration.

On defence, regimental artillery often is used on individual gun basis to provide close support and anti-AFV fire. In support group artillery standing barrages are assigned to each battery. Artillery is first used to harass tanks, separate infantry from tanks (long-range participates) and are usually assigned anti-tank barrages, and ultimately should be ready to be used for AT purpose via direct fire.

[Monster Fart]

oh my. good work. and lots of reading for me

[archibaldthe1]

Evidence that I have too much time on my hands (warning, this is very likely inaccurate in more than one way) - my attempts at a summary of how US arty would be used on-call when units were distributed to provide direct support (Bn, Reg and Div): https://imgur.com/K03R7fJ

[S'Aarum]

Very informative, thanks a lot for your work. Here take a reward. ^^