Bombard capability for (US) TD units (towed and tracked)

[GoodGuy]

In mid- or late 1944, particular Allied arty and a range of TD units (towed and tracked) increasingly performed unobserved fire missions, for interdiction/harrassment, which added to the missions aiming at locations - (daily) AARs of U.S. TD units (towed and tracked) are packed with descriptions of such fire missions.

The section quoted above is a part of one of my posts in the "seek and destroy" thread.
I suggest to add a bombard capability for US TDs (tracked and towed). Starting around mid-1944 (or even late 1943 or early '44, in Italy?), such units performed indirect-fire missions with HE rounds for interdiction or harrassment, the number increased to a level where then in autumn 1944 daily US TD unit AARs were filled with a myriad of such mission descriptions, eventually. The bombard capability should not able to answer to arty fire calls, but the user should be able to use them for interdiction/spamming manually, imho.

Background: the fast push through France and the loss of a vital amount of tanks and armored vehicles on the German side led to a situation where US (or Allied) TD units had a hard time to find any armored target, so their COs (or maybe even the higher echelons) ordered to employ such units in a bombardment role when they were "unemployed", purely for the lack of targets and as they would have been idle/useless, otherwise. Allied AA units experienced the same lack of targets, where then at least British AA units (who were not allowed to install the particular aiming devices for arty missions until very late 1944) seem to have been employed in a bombardment role starting around early 1945 locally, as well, eventually. I could imagine that British TD units also joined US TD units in their interdiction/harrassment roles, eventually, but that would be subject to research.
Anyway, I think a bombardment capability of the mentioned TD and (British) AA units would be historically and technically accurate and maybe it could be linked to a particular time frame (say starting in early or mid-1944 for US TD units, early 1945 for British AA units) in the game.
What do you think?

 

[ioncore]

The bombard capability should not able to answer to arty fire calls, but the user should be able to use them for interdiction/spamming manually, imho.

This would mean the feature is unavailable to the AI, as AI rely exclusively upon fire support missions to manage its artillery.

 

[jimcarravallah]

This would mean the feature is unavailable to the AI, as AI rely exclusively upon fire support missions to manage its artillery.

Even for the human player, the action should incur a severe targeting penalty because the tank destroyer crews had little training or background in beyond line of sight targeting. It amounts to tossing a huge load of TNT into a region on the hope that region contains a viable target.

 

[ioncore]

Even for the human player, the action should incur a severe targeting penalt

That would require modelling of the actual shell dispersion of an artillery piece. I have this in my personal backlog, but likely only for the next EF title.

 

[GoodGuy]

Even for the human player, the action should incur a severe targeting penalty because the tank destroyer crews had little training or background in beyond line of sight targeting. It amounts to tossing a huge load of TNT into a region on the hope that region contains a viable target.

You should read the article below (Field artillery journal), TD units got quite proficient in the arty support role. In the mentioned article, Major Ernest Hatfield also insists that TD troops adapted to their new roles quickly:

"Although initially crude, due to lack of precision instruments, the fire was effective and the tank destroyers accomplished many successful missions for the artillery. They were used to interdict roads, fire on enemy batteries, and knock out OPs at long ranges where organic artillery could not reach. Their fire became more and more effective with experience, and the mission of supplementing or supporting the fire of the artillery was accepted as a secondary role for tank destroyers."

Also, those TD missions were not restricted to interdiction/harrassment fire, I just named those mission types as examples, as the TD doctrine was adjusted in 1944 and training literature revised to include proper guidance for the secondary missions:

"1) direct or indirect fire missions to reinforce or supplement that of artillery units.
2.) Destruction of pillboxes and permanent defensive works.
3.) Support of landing operations
4.) Defense of beaches against waterborne attack.
5.) Roving gun and roving battery mission."
(Quoted from the revised tank destroyer Field Manual 18-5, dated 18 July 1944, paragraph 6)

Quote from the article in the journal:
"The following missions for tank destroyer units employed as reinforcing artillery were developed:
1) Reinforcing the fires of field artillery battalions.
2) Deepening and extending the zones of fire of the field artillery.
3) Targets of opportunity.
4) Counterbattery — to a limited extent.
5) Harassing missions.
6) Interdiction missions."

("Utilizing Tank Destroyers as Artillery", Maj. Ernest C. Hatfield, Cav., THE FIELD ARTILLERY JOURNAL)
http://www.tankdestroyer.net/images..._-_TDs_as_Artillery_and_TDs_in_Roer_River.pdf

 

[GoodGuy]

That would require modelling of the actual shell dispersion of an artillery piece. I have this in my personal backlog, but likely only for the next EF title.

If there'd be any penalty, then it should be linked to experience, only, if at all, experienced TD troops were totally used to that role. Please read the article (Artillery Journal) linked in my other post to keep this historical, as Jim's statement does not hit the nail there, unfortunately.

 

[GoodGuy]

This would mean the feature is unavailable to the AI, as AI rely exclusively upon fire support missions to manage its artillery.

Actually, I'd take my inital statement back. US TD units could actually be set to on-call state, but some code would have to make sure that there is a sufficient time frame between say returning from a patrol and setting up a support fire base (the unit should not be in say light woods and it would need ammo support for extra ammo expenditure). The unit could then answer to on-calls. Also, armored TD units didn't have the same communication sets as say towed TD units (with their field telephone lines, more powerful radios and extra personnel, etc.), so they relied on their radios to quite some extent, even for those fire missions, most likely, so their on-call duty availability should be reduced (if the engine allows to control that).

EDIT: If a bombard feature for TDs would be added (for the corresponding period in WW2), then it should be researched whether the other nations used their TD units in a similar manner.
Afaik, the Germans did not make widespread use of TD pieces/tanks in that role (single Panthers were used for such missions, though, with some artillery officers helping/giving advice), but the Brits did use TD and AA pieces for such missions to some extent, where their AA pieces even received precision instruments for bombardments in early 1945 (a few units/batteries may have violated rules by installing them before that point - as "illegal" field modification), as I outline in my first post.

2) Deepening and extending the zones of fire of the field artillery.

Since TD tank guns offered high(er) velocities, their max ranges were higher than the range of some arty pieces, as Hatfield outlined in the article. The (exact) max. ranges of TDs in the bombardment role would have to be researched.

 

[ioncore]

If a bombard feature for TDs would be added (for the corresponding period in WW2), then it should be researched whether the other nations used their TD units in a similar manner.

Soviets did that sometimes with SU-76 and occasionally with ISU-152 and ISU-122. Although all three SPGs were equipped with panoramic sights specifically for this purpose, firing indirectly was actually very rare - mostly because gun elevation angles were insufficient with all three. There are only two documented cases of Soviet heavy SPGs (122/152) engaged in such a way and a single known photo of ISU-152 performing indirect fire. More so of SU-76s, but, anyway, I wouldn't probably model that for Soviets at all.
UPD Ok, may be only for SU-76, as I've just checked some modern interview with former SU-76 crew member and he mentions that they have been training indirect fire intensively and actually used it in action (although he doesn't mention how often).

 

[GoodGuy]

Soviets did that sometimes with SU-76 and occasionally with ISU-152 and ISU-122. Although all three SPGs were equipped with panoramic sights specifically for this purpose, firing indirectly was actually very rare - mostly because gun elevation angles were insufficient with all three. There are only two documented cases of Soviet heavy SPGs (122/152) engaged in such a way and a single known photo of ISU-152 performing indirect fire. More so of SU-76s, but, anyway, I wouldn't probably model that for Soviets at all.
UPD Ok, may be only for SU-76, as I've just checked some modern interview with former SU-76 crew member and he mentions that they have been training indirect fire intensively and actually used it in action (although he doesn't mention how often).

I read about one ISU-152 case a while ago and thought that it must have been relatively easy to perform indirect fire with the ISU-152, as the ML-20S' second panoramic sight was the same sight as the one used on the ML-20 Corps (later on Army) gun (the Russians classified it as "cannon howitzer", I guess?). The Germans and the Finns captured several hundred ML-20, and the Germans redesignated and used them as 15,2-cm-Kanonenhaubitze 433/1(r) ("=cannon howitzer").
The 386. Otsap performed counterbattery fire on 12 January, 1945, during the Sandomir-Silesia Operation on a German fire base with 4 batteries, where the 152's supposedly fired 980 rounds and managed to suppress 2 German batteries in the process. Michail B. Barjatinski (in "The Big Game hunters - The Tiger Killers"?) wrote that 8 German arty pieces and a bn-sized infantry unit were wiped out. Is that one of those cases?
They had a range of 13 km only, since they had to use a relatively flat trajectory (the lower gun elevation turned out to be a problem), but weren't they actually supposed to serve as TDs AND as armored howitzers for advancing tanks? In the 1950s, they were supposed to fire shells with nuclear warheads and were still classed/used as tank howitzers until the 70s, afaik. No?
Anyway, since the capability was there and since the historical usage and training (on the SU-76 at least) is documented , then they (ISU-152 and SU-76) should be usable as "backup arty" and TDs in the game, imho.
The US TD units (towed and tracked) should deffo be classed as dual purpose units, and it should be researched whether the Brits also used their AA pieces and AT guns/vehicles for such missions on a somewhat wider level, or not, imho.

 

[ioncore]

wrote that 8 German arty pieces and a bn-sized infantry unit were wiped out. Is that one of those cases?

Yes. Of course, the actual effectiveness in this case could have been anywhere from zero to what Soviet AAR claims (and Barjatinsky quotes).

They had a range of 13 km only, since they had to use a relatively flat trajectory (the lower gun elevation turned out to be a problem)

This is exactly the point. What does it mean in practice can be easily explained using ML-20 firing tables, let's consider a rather typical bombardment range of 8 km:
- using full charge (V0 = 655 m/s) the fall angle will be 13° and the longitudinal deviation will be 36 m;
- using charge #1 (V0 = 606 m/s) at fall angle 16° deviation will be 35 m;
- using charge #3 (V0 = 560 m/s) at fall angle 19° deviation will be 33 m;
- using charge #5 (V0 = 462 m/s) at fall angle 25° deviation will be 29 m.
ISU-152 is not capable of using greater elevation angles or higher-numbered charges (with less propellant) to fire at that range, because that would require elevations beyond its construction limits.

Whereas a regular (towed) ML-20 could also fire:
- using charge #8 (V0 = 383 m/s) at fall angle 31° deviation will be 29 m;
- also using charge #8 at fall angle 68° deviation will be 33 m;
- using charge #10 (V0 = 335 m/s) at fall angle 36° deviation will be 32 m;
- also using charge #10 at fall angle 61° deviation will be 34 m.
So, as you and myself have already mentioned, the ML-20S (when installed at ISU-152) is not a gun-howitzer anymore, it is pure gun with pretty flat fall angles, meaning it can still be used against unprotected targets rather effectively, but it can not be as effectively engaged against entrenchments and other elements of field fortifications as ML-20 can, unless it is allowed of increased (or even extreme) shell expenditure. And, as a gun, it is only a mediocre one due to reduced firing range.

Add to this also the following important factors:
- while SU-76 units (both attached regiments and integral battalions) were used to support rifle divisions throughout all the offensive or defensive, ISU units were rather valuable and were usually attached either when German heavy armor (or massive amounts of armor) was expected to be met, or during the urban warfare (in both cases using them for indirect fire would be just a distraction);
- the shell capacity of the ISU-152 is very low (20 shells) and reloading the vehicle is long and cumbersome process given the huge shell size compared to the hatch sizes;
- the sustained RoF will be severely limited (compared to the towed piece) due to the ISUs' inadequate ventilation system combined with large gun caliber (inability of maintaining reasonable breathing conditions inside a vehicle during a sustained fire was one of ISU notorious features).
All these factors combined I suspect would be primary reasons why Soviets would employ SU-76s - which are open-top and therefore could be easily reloaded and ventilation is not an issue at all - for bombardment rather than ISUs.

Last, but not least, by 1944/45 due to improved (LL) logistics and narrowing front Soviets normally had adequate (or should I rather say massive & overwhelming) support from corps/army/front-level 122-203mm assets, which were far superior to ersatz-SPA by all means except protection.

but weren't they actually supposed to serve as TDs AND as armored howitzers for advancing tanks? In the 1950s, they were supposed to fire shells with nuclear warheads and were still classed/used as tank howitzers until the 70s, afaik. No?

Sure, but shifting the focus to SPA is already a post-war process, caused by:
- Soviet medium tanks' gun caliber reached 100/115 mm, making them significantly more effective against buildings and field fortifications (than in 1944/45) and relying less upon heavy assault guns;
- also medium tanks' frontal armor improved significantly, so that they were much more likely to survive the battlefield than ISU (which was, again, not the case in 1944/45)
- also, not only medium tanks became better, but also ISU themselves by 1950s became inadequately armored to be used as assault guns;
- finally, Soviet post-war excitement about nuclear weapons and mobile multi-rocket launchers made them to mass produce various kinds of TBMs and conventional MLRS, so that even aging and inadequate ersatz-SPA like ISU was okayish as long as it was supplemented by a massive rocket&missile counterpart.

Anyway, since the capability was there and since the historical usage and training (on the SU-76 at least) is documented , then they (ISU-152 and SU-76) should be usable as "backup arty" and TDs in the game, imho.

I'd say, until we stop consder only burst radius and introduce the modelling of shell dispersion and fall angles for artillery (which would also mean the real difference between employing guns and howitzers against dug-in/entrenched targets) AND rework our supply system, which is inspired by 1944/45 Western Front realities and is far too generous to properly model something like EF and especially the Soviet logistics there (emergency supply requests is a buzzword for Jim, but the problem is not limited to them), that'd only get Soviet side (players and AI alike) non-historically spamming 122-152mm left and right.
I'm not against it, of course, and I'm not a Russophobe, lol. I just try to value and consider the historicity of the overall gameplay over the historicity of individual features, while making ISUs capable of bombarding without changing the existing game ecosystem would just ruin it imho.

 

[GoodGuy]

1) All these factors combined I suspect would be primary reasons why Soviets would employ SU-76s - which are open-top and therefore could be easily reloaded and ventilation is not an issue at all - for bombardment rather than ISUs.

2) ....ISU units were rather valuable and were usually attached either when German heavy armor (or massive amounts of armor) was expected to be met, or during the urban warfare...

3) Last, but not least, by 1944/45 due to improved (LL) logistics and narrowing front Soviets normally had adequate (or should I rather say massive & overwhelming) support from corps/army/front-level 122-203mm assets, which were far superior to ersatz-SPA by all means except protection.

These 3 points are most likely the most important factors in the Russian thought process (and reasons to rather employ the low-calibre SU-76 than the bulky and labor-intensive ISU) you mentioned, so it looks like the ISU could be x'ed from the list (until the engine issues are solved + some engine capabilities extended), but the SU-76 should be included, just like the US TDs, imho.

ISU units were rather valuable and were usually attached either when German heavy armor (or massive amounts of armor) was expected to be met, or during the urban warfare ...

In Berlin or Königsberg, they would carefully advance in pairs and roam through street after street hitting road blocks, sniper hideouts and strongpoints, while being exlusively covered by dedicated infantry squads who provided flank protection and who cleared houses to keep the ISUs safe, the whole time. There's some footage from Berlin showing that strat. I wonder if such setup could be included in the EF estabs, in case some community scenario designer would want to cover the Battle of Berlin.(*hint)

Looking at the ammunition mainly used by the SU-152 (mainly HE) and at the rather low availability of AP rounds used by both (ISU + SU 152) tanks, I see a role rather leaning towards a direct-fire assault gun role (and maybe - as rather rare "third" choice - arty support) than to a TD role for those tanks, due to their devastating HE fire power, imho. Since the knocking power (as in HE blast power) of the shell could rip off the turrets on German tanks, the tank could still serve as potent TD at certain distances, ofc. While the SU/ISU could damage German heavy TDs and incapacitate (or even kill?) their crews, it couldn't destroy them, though, the Germans retrieved such TDs, repaired them and just put them on the line with new crews - the next day.

That brings up the next question. Will the engine be able to cater for lightly damaged tanks that can be repaired within the scenario time frame (say 2-4 days repair time, in a 9-days scenario) some day? The Germans had an excellent record of retrieving damaged/wrecked tanks, and even the Russians managed to retrieve a number of tanks after Kursk, when they regained access to the territory.

I'd say, until we stop consder only burst radius and introduce the modelling of shell dispersion and fall angles for artillery (which would also mean the real difference between employing guns and howitzers against dug-in/entrenched targets) AND rework our supply system, which is inspired by 1944/45 Western Front realities and is far too generous to properly model something like EF and especially the Soviet logistics there (emergency supply requests is a buzzword for Jim, but the problem is not limited to them), that'd only get Soviet side (players and AI alike) non-historically spamming 122-152mm left and right.
I'm not against it, of course, and I'm not a Russophobe, lol. I just try to value and consider the historicity of the overall gameplay over the historicity of individual features, while making ISUs capable of bombarding without changing the existing game ecosystem would just ruin it imho.

Since you mentioned the fire tables: The towed ML-20 would fire at a high angle (means near its ~65° or 68° limit) and with a load number somewhere between #8 and 11#, I guess, in order to effectively hit trenches/strongpoints, so an ISU unit would deffo be less effective (or even ineffective) in an indirect-fire low-trajectory role against such positions, so I suspect that COs rather refrained from calling in ISUs for arty missions.
But still, weren't the ISUs concentrated in those Guards heavy SPG artillery units and wasn't that at least the initial triple-purpose idea, in late 1944, to get the tanks some mobile arty support (next to having a capable assault gun and an effective TD - with HE)?

Still, I wonder what would happen if ISUs in the game would receive some toned down indirect range (say 6-8 km) and some extra code (neither the AI nor the player could override) that would switch to reserve ammo for direct fire missions after say 10 rounds (= 10 indirect salvos)? Then the AI/player wouldn't be able to turn the game into a spam fest. Maybe ammo support for ISUs could be tweaked, as well, so that the delivery of a new loadout wouldn't occur every few cycles, no?
The AI code could also be modified to treat ISUs as low priority arty, which is only supposed to be used in emergencies (say on ambushes), the code for the player would then grey out the bombard button and only make it available if an ambush is detected. Stuff like that. Would something like that be feasable?

 

[GoodGuy]

"Although initially crude, due to lack of precision instruments, the fire was effective and the tank destroyers accomplished many successful missions for the artillery. They were used to interdict roads, fire on enemy batteries, and knock out OPs at long ranges where organic artillery could not reach. Their fire became more and more effective with experience, and the mission of supplementing or supporting the fire of the artillery was accepted as a secondary role for tank destroyers."

I'd like to add something here: A while ago, I searched for some US TD units as they were advancing/deployed in an area not too far from my hometown, which caught my interest. During my research, I found some AARs of these units and stumbled over a shyteload of indirect-fire missions in there, where many of them - to my surprise - were carried out daily or even several times/day. The more daily AARs (TD units in the Aachen - Cologne - Bonn area and other sectors) I checked the more TD arty missions I found. I found an AAR resource covering September '44 to around February or March 1945 (iirc) and figured that quite a few TD units had been employed that way, some started around December, others as early as Sept. or October (iirc), with an ever increasing number of such missions. There were so many missions, just in all those AARs of 2 or 3 TD units, and while I was trying to find more I got so tired that I almost fell asleep on my keyboard (lol), as I was pretty eager to find out which other units and how many other units employed such arty support regime, so I couldn't figure the exact number in the end.
I think I posted my finding here in some thread, though, and I think I posted parts of those original AARs, as well.
If needed, I could try to dig for my bookmarks (and Nara scans I found along the research sessions), but I have no doubt that by around October or November '44 the additional regime/role was widely applied/accepted, as armored targets had become rare at the time. It must have been common in Italy before, already. If I am not mistaken, some AARs were from TD units deployed in Italy, too, but I'd have to double-check.

 

[ioncore]

but the SU-76 should be included, just like the US TDs, imho.

Agree.

I wonder if such setup could be included in the EF estabs, in case some community scenario designer would want to cover the Battle of Berlin.

Sure, why not, something like "Urban Assault Company" (or Platoon, or Group) would definitely make sense.
Have in mind though, that there will be no single EF estab, that would be just unmanageable. The "official" EF estabs will be split by periods, and the one to be first released will only cover the 1936-1940 timeframe, meaning (potentially) Fall Weiss, (potentially) Winter War and (Kh-G DLC) various Soviet-Japanese conflicts.

Will the engine be able to cater for lightly damaged tanks that can be repaired within the scenario time frame (say 2-4 days repair time, in a 9-days scenario) some day?

Any major Soviet-German "tank" DLC would require recovery/repair feature imho (and this is one of the reasons why we have started with Mongolia first, as it required less new features, yet offering a good enough testbed for Soviet equipment, estabs etc).

But still, weren't the ISUs concentrated in those Guards heavy SPG artillery units and wasn't that at least the initial triple-purpose idea, in late 1944, to get the tanks some mobile arty support (next to having a capable assault gun and an effective TD - with HE)?

No, I haven't seen such intents mentioned anywhere. For SPGs it is usually written, that the primary reason for panoramic sight to be used was not the indirect fire per se, but rather that the telescopic sight ST-10 (used on SU-152 and then later on ISU-152, as well as the equivalent ST-18 sight used on ISU-122) were calibrated only up to 900 m (i.e. for a direct shot), so that for firing at anything beyond that range (directly or indirectly) the panoramic sight had to be used. It is also mentioned that at least the ISU-122 crews were particularly not fond of the panoramic sights, (their placement in the vehicle was unfortunately preventing gunner from using telescopic sight efficiently and also blocking driver's way out of the vehicle) and some of them have been even dismantling panoramic sights before the combat.
Also note that all Soviet mid/late war heavy tanks - KV-85, IS-1, IS-2 - have been equipped with panoramic sights and could fire indirectly, too (not sure if it was because of the same calibration issue as with SPGs, or because just why not, lol). IS-2 even had special mil markings around the turret ring to facilitate indirect fire, but we probably aren't going to discuss adding a bombardment capability to Soviet heavies.

some extra code

That's the keyword here. There's currently no purpose/effectiveness/priority logic for arty support, meaning all units capable of firing indirectly are treated in the same way. Of course, there is a code responsible for telling whether the unit is able to fire at all at the given moment, with a lot of things considered inside, but that is a binary decision and there're no such things as "better/worse" or "high/low prio" there. We'd need to introduce some new decision-making in that domain.

Would something like that be feasable?

Yes, why not, if we're really keen to model this at some point.

 

[ioncore]

Would something like that be feasable?

Also one may, even now, resort to the simplest solution of adding bombardment cap to the ISUs with an extremely low RoF (like just one shell in several minutes). That would be the lesser evil, although it'd still mean all ISU units will now start firing indirectly on fire support requests left and right, albeit very slowly, thus making the end effect and the play experience the same unhistorical. So *some* changes in the code are absolutely necessary.

 

[GoodGuy]

Agree.


Sure, why not, something like "Urban Assault Company" (or Platoon, or Group) would definitely make sense.
Have in mind though, that there will be no single EF estab, that would be just unmanageable. The "official" EF estabs will be split by periods, and the one to be first released will only cover the 1936-1940 timeframe, meaning (potentially) Fall Weiss, (potentially) Winter War and (Kh-G DLC) various Soviet-Japanese conflicts.

I know that Dave is quite busy coding, so I really appreciate that you take the time to reply to such requests/questions, I also like the fact that you drop stuff like the rough release plans/ideas, and that you explain code capabilities or shortcomings - blended with your own thoughts on things. Dave owes you one or another appreciative pat, there.
And such "drops" keep my hopes up that mounted ops will come, some day.

Any major Soviet-German "tank" DLC would require recovery/repair feature imho...

YUMMY !

No, I haven't seen such intents mentioned anywhere. For SPGs it is usually written, that the primary reason for panoramic sight to be used was not the indirect fire per se, but rather that the telescopic sight ST-10 (used on SU-152 and then later on ISU-152, as well as the equivalent ST-18 sight used on ISU-122) were calibrated only up to 900 m (i.e. for a direct shot), so that for firing at anything beyond that range (directly or indirectly) the panoramic sight had to be used. It is also mentioned that at least the ISU-122 crews were particularly not fond of the panoramic sights, (their placement in the vehicle was unfortunately preventing gunner from using telescopic sight efficiently and also blocking driver's way out of the vehicle) and some of them have been even dismantling panoramic sights before the combat.
Also note that all Soviet mid/late war heavy tanks - KV-85, IS-1, IS-2 - have been equipped with panoramic sights and could fire indirectly, too (not sure if it was because of the same calibration issue as with SPGs, or because just why not, lol).

I knew some of the details, but not all of them, interesting ... Soviet heavy TDs/regiments are far from being my hobbyhorse.
Quite a few of the (let me call them "non-heavy" or regular) SPG regiments (ie. the 4-digit ones) seem to have evolved from "destroyer" AT Bns or mobile armored units (eg 5th Guards), some Heavy SPG regiments were formed using personnel or skeletons from tank units, which suggests a non-artillery background on the crews' side. What SPGs were used in those regular (non-heavy) SPG regiments?
So the original intent was "only" a dual-use (SU/ISU) from the get-go, means as very potent assault gun and as capable TD (with HE, and IF HE rounds hit the right spots)?

IS-2 even had special mil markings around the turret ring

You mean markings on the reticle for elevation, not the turret ring, I guess?

Also one may, even now, resort to the simplest solution of adding bombardment cap to the ISUs with an extremely low RoF (like just one shell in several minutes).

That's actually what I had in mind, at first, but then I thought that it would be a) too simple and b) it would put an unfair/unhistorical handicap on their RoF when facing strongpoints or enemy tanks/inf, without code changes.

 

[Grognerd]

Any major Soviet-German "tank" DLC would require recovery/repair feature imho (and this is one of the reasons why we have started with Mongolia first, as it required less new features, yet offering a good enough testbed for Soviet equipment, estabs etc).

Interesting indeed! Nice feature too.

 

[ioncore]

I know that Dave is quite busy coding, so I really appreciate that you take the time to reply

Yes, I must admit I also quite enjoy the working model where Dave has to do all the dirty AI programming leaving me responsible for talking and all the fun stuff in general.

Quite a few of the (let me call them "non-heavy" or regular) SPG regiments (ie. the 4-digit ones) seem to have evolved from "destroyer" AT Bns or mobile armored units (eg 5th Guards)

Roundabout half of these (may be more) were formed from scratch. The rest were created out of (sorted in the order of decreasing number of cases):
- AT Regiments (many of these retained their numbers, e.g. 1505th AT Regiment became 1505th SPG Regiment etc);
- AT Bns ;
- independent Tank Rgts
- independent Tank Bns
- and at least one regiment was created out of a non-independent Tank Bn (140th Tank Bde together with its 1st Tank Bn was reorganized into a 14th SPG Bde while its 2nd Tank Bn became 867th SPG Rgt).
Also, there were quite a few SPG Bns formed in late 1944 - early 1945. These were integral to Rifle Division and were often created by reorganizing that particular Division's towed AT Bn (not dissimilar to German practice of having one Coy of an Pz.Jg.Abt armed with TDs), or created from scratch.

some Heavy SPG regiments were formed using personnel or skeletons from tank units, which suggests a non-artillery background on the crews' side

All the original (non-Guards, armed with SU-152s) Heavy SPG Rgts were created from scratch.
Most of the Guards Heavy SPG Rgts were created in 1944 by (sorted in the order of decreasing number of cases):
- promoting from non-Guards Heavy SPG Rgts (and upgrading from SU-152 to ISU-122/152);
- reorganizing from Heavy Tank Rgts (armed with KVs or Churchills) or Tank Rgts (armed with T-34s and T-70s);
- promoting from non-Heavy SPG Rgts;
- reorganizing from the units of some Tank Brigades.

So non-Heavies (Rgts and Bns combined) were usually newly created units, or former anti-tankers, or former tankers.
Heavies were either (early on) newly created units or (later on) former tankers or SPGers (more often Heavy tankers/SPGers than not).

What SPGs were used in those regular (non-heavy) SPG regiments?

At the beginning these were SU-76, SG-76 and SU-122, later (late 1943 and beyond) also SU-76M, SU-85, SU-100 and M-10. But SU-76/76Ms were kind of dominating species.
All the SPG Bns were armed exclusively with SU-76Ms. At least I'm not aware of any SPG Bn armed with anything else.

b) it would put an unfair/unhistorical handicap on their RoF when facing strongpoints or enemy tanks/inf

It won't, as bombardment has its own RoF (separate from anti-armor and anti-personnel fire).
As a sidenote, having separate RoFs for anti-armor and anti-personnel is also very neat feature, as it allows e.g. to model lower anti-armor effectiveness (lower anti-armor RoF) for field artillery pieces which had two gunners - one responsible for vertical aiming and another for horizontal aiming - which made these guns difficult to aim at oblique fast-moving targets (like tanks etc).
A lot of design decisions in CmdOps2 are very smart and make perfect sense. This is, I guess, the reason why, after all these years, we're still staying around.

 

[ioncore]

You mean markings on the reticle for elevation, not the turret ring, I guess?

No, I mean exactly the turret ring, all-around the turret inside the tank. I can't find these on the modern IS-2 interior photos so these were probably just paint markings. I guess the idea was that the crew could rotate the turret to a given number of mils even without using any kind of Messgeräte.

 

[GoodGuy]

No, I mean exactly the turret ring, all-around the turret inside the tank. I can't find these on the modern IS-2 interior photos so these were probably just paint markings. I guess the idea was that the crew could rotate the turret to a given number of mils even without using any kind of Messgeräte.

Erm, this is the gun sight of the T-34-85:

There are 2 explanations floating around regarding the etchings on the reticle, but I believe that the variant saying that the long horizontal line (indicating the gun elevation) was fixed (tied to the gun's elevation), and that the scales on the left moved down once the gun was elevated, is the right explanation. The other variant insists that the range scales on the left were fixed and that the horizontal line moved up while the hashmarks moved down when the range was adjusted.The 2 scales on the left were supposedly used for AP (number column on the left side of the horizintal mils) and HE (right column), the scale on the right side of the reticle were for the MG, supposedly.

The Russians studied the German reticles and tried to copy them, they also tried to figure their measuring system (which was pretty much the system outlined in the Tiger manual) which just involved some math (where the crew helped the gunner/commander to calculate distances for the amount of mils (pyramids, means: size of object in mils = distance), or where they could even shout out memorized common distances in meters right away; the crew also received tables with common distances/visors, so that the gunner just had to pick a particular "visor" setting (means elevation value) - say 4 - for a particular distance and fired right away, without having to calculate the visor setting). The Russians took over the "pyramide" mils, but I am not sure if they actually used them for measuring distances (like the Germans) or just for leading the aim on moving targets.

The IS had a similar reticle:

So, if the horizontal line moved up (or the scale down, it doesn't matter), then the IS-2 could have easily performed indirect fire (up to a certain elevation, at the end of the scale).
It would be nice if you could point me to a picture with "inside mils", if you ever stumble over one. I could imagine that the crews painted them inside to cover higher elevations/ranges. German crews just had their tables, as well as their individual notes/table appendices which they had to learn by heart, but which they could also calculate anytime, up to ~3,000 or 3,500 meters). For indirect fire (and long distances), the Germans usually needed some assistance from an artillery officer, who would then help to measure the fire base and align the tank gun to the Zero position. I think I outlined the procedure here, somewhere in the LnL forum.

 

[ioncore]

@GoodGuy you go into lot of details for ranging, whereas the sources clearly say that mils marking were made all around turret ring, meaning they were used for horizontal aiming, not for ranging.
Also, I think I've found the missing piece of a puzzle: the panoramic sight (PT4-17) was removed from IS-2 model 1944 and replaced with just another periscopic MK-IV observation device, leaving IS-2 only with the telescopic sight TSh-17 (which you've shown above). I think this is highly likely the reason why these mils markings would be introduced together with the spirit level (which also had mils precision). So, with the removal of panoramic sight these markings would be the only mean to aim the turret horizontally and with the spirit level the vertical aiming would be possible (both with mil prevision) for indirect fire.
So what the sources likely omit is that there was either panoramic sight (before model 1944) used for indirect fire, or markings and spirit level, but not both.