HerrTom

Sixth & Seventh Minutes
 “Take calculated risks. That is quite different from being rash.”
George S. Patton
 
Warren continues to stick his nose out… this time it’s a standard  BMP-1P that is spotted by a tank from Tank Section 2…


…from top to bottom:  M-60A1(RISE+) (1/6) fires one APFSDS round, which misses, but does inflict one casualty… then quickly followed up by two HESH rounds... though the first of these was all it took to kill this BMP.
Range:  1270m

There are now at least four infantry or recon teams moving towards Dolbach, and one of those looks like an HQ... so either one full platoon, or parts of two.  They have a long way to go yet and they are on foot so I expect they’ll be getting tired by the time they get there.
 Planned welcoming party:
·         I have pushed Scout 1’s M113A2 forwards to get a gun laid on their route
·         I have plotted a mortar strike in front of them… set to hit in about three minutes

A quick note, I am still biding my time here and gathering information.  Warren is being very cautious… I expected him to be a little more aggressive, and he has probably received his first reinforcements too so I will probably see some tanks soon, and the aggressiveness will ramp up.  I need to wait a bit until I get more information prior to moving on incomplete information. 
That said, I am going to move both of my M-150s into better positions to try and bag one of the BMPs I can see in the tree line yonder.

I love this game, by far the most playable game of its type I've seen. Only one I actually finished a game with (major Soviet victory, I trounced my opponent!). There's also The Next War: Modern Conflict in Europe (1978). Never finished a game of that one, though (the continuation of the series by GMT is much better IMO).  If you want to drill down to the corps level there's also Less than 60 Miles by Thin Red Line that came out recently with some really interesting C3 mechanics in it.
+1 to this. Dry, but immensely informative, and likely a lot more accurate to the time period of this game than the field manuals or other writings from much later.
There's also Dave Glantz's The Soviet Conduct of Operational Maneuver that covers the history and development of modern Soviet operational thought.  Soviet AirLand Battle Tactics by William Baxter is also a solid work (don't let the name fool you - he wrote it to be more "approachable" by western officers). Not as dry as many others, too.

I love this game, by far the most playable game of its type I've seen. Only one I actually finished a game with (major Soviet victory, I trounced my opponent!). There's also The Next War: Modern Conflict in Europe (1978). Never finished a game of that one, though (the continuation of the series by GMT is much better IMO).  If you want to drill down to the corps level there's also Less than 60 Miles by Thin Red Line that came out recently with some really interesting C3 mechanics in it.
+1 to this. Dry, but immensely informative, and likely a lot more accurate to the time period of this game than the field manuals or other writings from much later.
There's also Dave Glantz's The Soviet Conduct of Operational Maneuver that covers the history and development of modern Soviet operational thought.  Soviet AirLand Battle Tactics by William Baxter is also a solid work (don't let the name fool you - he wrote it to be more "approachable" by western officers). Not as dry as many others, too.

Not books but a lot of games in the 80's were based on the Cold War gone hot
Red Storm Rising (C64), Project Stealth Fighter (C64), Red Lightning (Amiga), The Third World War "Battle for Germany" (Boardgame).
Add to that Judge Dredd, the future after the third world war.
Yup, that's my childhood growing up in the 80's listening to Mötley Crüe, Helloween, Doro Pesch, Nitzer Ebb, Front 242, etc. playing games and reading Tom Clancy

If you are looking for some generally informative information I would highly recommend this blog: https://coldwargamer.blogspot.com/
There is mountains of great material to sift through there, plus some nice model pictures here and there if you're into that sort of thing. 
For more fun reading, "The War That Never Was" by Michael Palmer is great. "Northern Fury: H-Hour" by Bart Gauvin and Joel Radunzel is also great and is based off of a computer wargame (Command: Modern Operations). "Red Army" by Ralph Peters is the Russian version of Team Yankee, written from the perspective of the Russians, and it also quite good. And then there is "The Defense of Hill 781" by James B. McDonough for those looking to get an NTC perspective. 
I'm certainly missing some more that are good, but everything mentioned here in this thread is certainly worth your time. 

From FM 71-1 (1977)

Fourth Minute - First Contact!
Forgive me for a second AAR post today, but I will be traveling tomorrow and wanted to get this one published tonight.
 
“One should not be diverted by geographical objectives, but should concentrate on the destruction of the enemy’s military forces.”
Classic Russian Military Principles
 
A little excitement during this turn, and first shot fired (all times are in Game Time, counting down from 40:00).  Yellow text for contacts equals a tentative contact, red text is for solid identified contacts. 
@36:47:  Early in this minute M150 (1/5) got a firm spot on an enemy BMP moving to the edge of the woods, then immediately lost the contact as it continued forward slightly.  Positive ID: BMP-1P.  Note:  this is a resolution of the tentative spot from the third minute.
@36:35:  M150 (1/4) noticed some movement near NAI3.  Appears to be a light armored vehicle, suspected to be a BMP.
@36:21:  The 36:35 spot becomes a positively identified BMP-1P as it nosed slightly out of the treeline.   This BMP is oriented directly toward M-150(1/4) but does not have a spot, it could be overwatching the ridge the Tank Hunter is sitting on.

Note the type of ATGM (AT-4 I believe) and the mast antenna.  The ATGM makes it a BMP-1P, the mast antenna makes this a BMP-1PK, a Company Commander's personal ride.  One Company HQ identified... make a note.
As the BMP halted at the edge of the treeline it gave M-150 (1/4) enough time to aim and loose a TOW, which alas, fell well short of the mark probably due to my smoke screen.  The contact was then immediately lost, probably due to the smoke, missile destruction debris etc.

With any luck, the enemy commander will have missed the missile launch and will think the missile’s impact with the ground is a spotting round.

@36:04:  M150 (1/4) noticed some movement within NAI2.  Appears to be a light armored vehicle, suspected to be a third BMP.  One full Company or parts of two?  Time will tell.  
Only one adjustment was made to my positions this turn.  After a quick check, M-150 (1/4) is only Partially Hull Down to the BMP it fired at this turn so will be reversing into a full Hull Down position to this enemy vehicle, and will also be narrowing its cover arc to focus on the location of this enemy BMP.
A note about Hull Down… just because you are Hull Down to one piece of ground, does not mean you are Hull Down to another.  You should check and recheck this as a scenario unfolds, especially when you have firm contact sightings.

Bil
COMING UP NEXT:  The Return of the Famous Blood Board!!

First Three Minutes!
 “Perception is strong and sight weak. In strategy it is important to see distant things as if they were close and to take a distanced view of close things.”
A Book of Five Rings, Miyamoto Musashi
 
The initial phase of this action will be me positioning my units to get eyes on the most likely enemy avenues of approach, especially EAA1 (NAI 1). 
After two minutes of action:
M113A2s and Scouts: Reached their drop off points and the two Scout teams have dismounted and are continuing on foot in order to get into positions where they can look into EAA1.  The Platoon Leader will stay mounted in his M113 for now.

M-60A1 (Rise+) Section 1:  Arrived in hull down positions with views of NAI 2 and 3. M-60A1 (Rise+) Section 2:  Arrived in hull down positions with views of NAI 2 and 3. Tank Section 1 moves into position:


M150 TOW Tank Hunters:  Both now in hull down positions overlooking NAIs 2 and 3.
Artillery Smoke Screen:  After two minutes I have cancelled the fire from both batteries.  Mainly because I want them available once my Scouts start to see into NAI 1.  The screen should build for a few more turns as laid then should last for several more.  It’ll be interesting to see how effective it is at messing with the Soviet spotting-targeting cycle.
FIRST ENEMY INDICATOR:  In the third minute M150 1/5 (1st Platoon, 5th Vehicle)) noticed some movement in the woods between NAIs 1 and 2.  Nothing is known about this contact other than that it is a light armored vehicle, suspected BMP from the Recon Company.

Now to place this image in context... in case you ever wondered what a Hull Down M-150 Tank Hunter looks like from the Soviet perspective:

Bil

Not much differently from 1945 either Bletchley. Apply firepower, then a little more, and once the heavy guns are dry, send some bullets. Then send men, but not prior to flattening the grid square. If you're using an Armored Division troop, apply all of the above, but send a tank between the bullets and then the man step. Tactically the US Army looked pretty good, and was second only to the Red Army in being subject to the least of post-war cuts and expenditure reductions-which were still quite substantial nonetheless. US Army Divisions had all of their artillery batteries augmented from 4 guns to 6 after the war, however some of the expansions in US heavy firepower were offset by Soviet improvements in their own artillery parks. So unlike the Wehrmacht US Infantry would be facing much more serious threats from counter-battery and preparatory fire this time around. The BM-21 is not a terribly sophisticated piece of equipment but God, they sure got a hell ofa lot of em! 
Much like the Wehrmacht, it seems that much American thinking was now oriented toward strong-point style defense which would hopefully nullify much of the consequence of the heavier fire by simply not presenting any target. Then of course the Armored Divisions would have many built in advantages against that but much like the conundrum facing the Panzer Divisions in 1944- how many of those do you have? You've got 7th Army. Group Soviet Forces Germany alone is seven Armies. 
What's the promise of defeating the Red Assault with strings of infantry in blocking positions and counter-attacks by Armored Divisions to plug gaps? If 1945 is any hint, it's not good-but there's room for frustrating time-tables and slowing down the enemy's advance. This was a big element of the REFORGER exercises after all ie: hold on until the cavalry arrives. In this frame there's quite a room for Combat Commands/Brigade Combat Teams to work around inside of. If Bill's force looks like the buffet table at the Shoney's that's because his force is a post ROAD (Reorganization of Army Divisions) command. IE: It's all Brigade Combat Teams, not Regiments. So the structure is closer to 2007, but the execution will still look more like 1945. 

Love to see a module featuring or focused on French forces of NATO... 

March to Glorious Victory Post Number One.
  So Bil and I have a loose-agreement (I would say gentlemen's but that is probably a stretch) to not peek at each others threads.  The dirty truth here is that this isn't really an AAR per se, it is more of an IAR (In Action Report).  Full disclosure, we are only about 6 mins into the thing, so I can't really put a spin on my plan or anything because I have no idea how this will end.  So far so good  but we are in early days.  We should start posting turn summaries tomorrow but for now may I present an end-product of about roughly 32 years of military training in both line and staff positions...The_Capt's glorious Mission Analysis!  
So here we are on this grubby little peice of West German real-estate (seriously, Pete Wenman is a freakin wizard with these maps btw) facing off against what I am sure are overfed, overpaid and over-entitled Yankee capitalists all huddled in their vehicles waiting for something to happen.  So like they taught me back in the day..let's start with terrain:

So my guys are coming from the bottom, Bil and his jerks are up near the top.  I have a bunch of woods except for this defile behind a hwy bridge that I have to deploy my main force out of.  We have a big valley between us and the town of Dollbach in the center which is the golden goose we are both lining up to grab, whilst killing the other guy.  Not much to see on my map edge except a bunch of woods with some dirt roads cut through them.  
Bil has the high ground ridge up there and there are three major wooded areas that him and his ilk are no doubt hiding out in.  It is more one on the left but pretty much that approach along with the Valley is dominated by Bil's thugs.  In short, this is not an optimal starting position.
Bil's Plan.  So I have learned some time ago that you are not fighting vehicles and equipment, you are fighting a person (Capt's rule #1).  So spend time understanding and getting inside the head of that person.  With Bil it is easy because we have been sparring in CM for just about 2 decades now.  So here is what I am thinking, that Bil is thinking:

So Bil is probably going to be cautious and build a nice path to victory here.  First he is going to put out Eyes in those woodlines, then he will reinforce with teeth because why stick his neck out if he does not have to?  Then once I have watered the West German countryside with my blood (and other fluids) he will make his reach for Dollbach (Hands...dirty, old, wrinkly hands with yellow fingernails).  I will be at a significant disadvantage at this point because I will be dead, and you do not fight so well when dead (Capt's rule #2).  So my role here is to play peeky snipey from a really crappy position with Soviet gear that does not see as well as his sexy US optics...hmm...Capt no-likey, no likey...one bit.  So now the Plan:

My end goal is to make Bil more dead than me, not to get heavily invested in the West German real estate market.  So we are going to try something simple and blunt.  First, I will get Eyes on my woodline, gotta see what I can see (Capt's Rule #3).  Then I am going to put out hands...fingers really, to make it look like the land grab is my only game.  Then once my art start dropping (could be wait here cause he has EW turned on), I am going to bull rush that corridor and swing up into those hills to kill Bil (Teeth).  This is going to be tricky and I am going to take losses but I can afford them.  I get a MIC FSE in 5 and another Tank Coy-ish in 10, so I will have mass because I am betting the best he has is an Armd Cav platoon, maybe two.  So basically we will play Bil's snipey peeky game for a bit, push recon out into that town to make me look desperate and then freakin charge on the left.  Questions?
 

Ok, lemme weigh in on this because there are going to be more questions.  What made it into the game...and why?  What did not make it into the game...and why?  Not easy answers to be honest.
First we took a deliberate design choice to try to stick to a policy of "historical introduction +/- 6 months".  The primary reason was to not artificially limit the choices of the player and leave more constraints/restraint decisions in their hands...they are the customer.  There will be purists out there - god love em- who will want to play with extreme historical accuracy and this game is set up for that.  Then there will be 'experimenters' that will want to see what happened if X showed up earlier/later, so we took a look and tried to keep the aperture open for them too.
Second, unlike most historical conflicts, the Cold War never went hot so the geopolitical or strategic situation never really evolved to mirror what is happening in our game.  For example, having spent a lot of time looking at committee records and  logistical after action reports, the reason that vehicles or weapons systems were introduced at a certain date was not the same context as, say, WWII.  These were not shaped by technical, industrial or operational realities as much as they were by good old fashion bureaucracy.  Vehicles and equipment were held up for funding shifts or strategic logistical SNAFUs, not anything "real".  So within a "what if" context saying "Nope the M2 Bradley cannot be in Europe in 81-82...sorry player" makes no sense if the primary reason was "it got delayed because we forgot to include a support package"  or "there was a congressional district issue"  or "the delivery process got held up in a contracting screw up".  If there had been an escalating strategic reality, all of this red tape would have been cut through and the vehicles, which were being manufactured (i.e. well past the prototype stage) and many of them in warehouses, could have easily been pushed forward.
So what?  Well if you see an odd vehicle date to your eyes, trust me we know about it and considered it.  If you want to play with the highest historical accuracy possible you can do that easily within the game.  If you wish to push the envelope of what could have been, well you can do that too...within reason.  You will not be seeing M1s rolling across the plains in 1979, there is a point between ahistorical and complete fantasy but some equipment, particularly US will be available earlier or later than its actual arrival date in the ETO but all of these vehicles were 1) well into manufacturing and 2) had been already delivered to the US military, contracts cut and the machine in motion.  
And finally, what got left out.  Ya, there is simply no way we were going to win this one...we still get beat up by the beta team for leaving out vehicle Z.  Here the tyranny of time kicks in.  Spending an extra 6 months modeling and testing in-game systems that were niche and that most players will never see or use, simply does not make sense.  And then some pieces of equipment would break the game engine itself (e.g. AVLB...breaks my heart as an engineer).  So hard decisions to leave some babies on the roadside had to be made...and they were.  What is in the game are the essentials (plus) and we are likely going to have disagreement on what was "essential"...now let the healing begin.

I hope Bil doesn't mind but the evolution of the Dollbach map. Note the map image predates the autobahn and bridge. It also gives an overview of the battlefield for those that like that kind of detail

P
 

Always the dog first isn't it.....If he doesn't come back, then the missus comes to check (on him, I strongly suspect). 

This is something I threw together in my own time. Please remember that this is from a beta build of the game and is subject to change. 

“Here, across death’s other river, the Tartar horsemen shake their spears.”
T.S. Eliot
 
This BETA game is being played against Warren (The_Capt), and we are very familiar with each other’s style, strengths and weaknesses as we’ve been playing CM against each other for close to 20 years now.
CM Cold War was our brainchild and has been on our wargame design table, off and on, for eight years now, but now it is a real thing.  You’re welcome.    With that said it is only fitting that Warren and I play in this BETA AAR.  We haven’t played in public since our original CMBN BETA AAR, Not your Father’s Combat Mission. 
I hope you enjoy the ride, and welcome to the COLD WAR!!

Sidebar!  I strictly use the Movie Mode when I play so all of my screenshots use that feature.  I don't mean it to insult anybody, but I just think the game looks better.
Meeting Engagement at Dolbach Heights, 1980
When Warren and I laid out the design for this game we wanted it to be primarily and ultimately a sandbox for experimentation and reflection.  A tool to test the tactical theories that were prevalent at that time.  Time… yes, we also wanted to be able to examine the different sides from different time perspectives, and this release, the base game in the CM Cold War series, contains the years 1979 to 1982.  We also only cover the months March to October, mainly so we didn’t have to generate winter textures and models which would have been one feature too many.
This particular scenario is one that Warren and I threw together that we thought would be fun to play and show off.  The map is from the US Campaign and when you play that you will see this map eventually.  I will start my METT-T analysis in my next post, but for now, sit back, enjoy the existence of this game, and don’t go away!
Bil

CONTENTS:
METT-T Analysis MISSION ENEMY TERRAIN TROOPS / TIME Tentative Plan The Action: First Three Minutes! Fourth Minute - First Contact! Fifth Minute - Return of the Blood Board! Sixth & Seventh Minutes Eighth Minute - One Meter Too Many Eighth Minute - BDA & Some Movements Ninth Minute Tenth Minute Eleventh & Twelfth Minutes - "...damn your eyes." Thirteenth Minute - The Board is Set Fourteenth Minute - Spoiling Attack Plan Fifteenth through Seventeenth Minutes Eighteenth Minute - Relearning Old Lessons Nineteenth & Twentieth Minutes Twenty-First & Twenty-Second Minutes - Beyond Here, There be Dragons Twenty-Third & Twenty-Fourth Minutes - Saga of Tank Section 1

Still plugging away at this.  Found an interesting tidbit while researching tinkering around with war simulations in MATLAB.
http://www.dupuyinstitute.org/pdf/v1n6.pdf
Pages 26-29 talk about tank loss rates from artillery fire in WWII.  Through 7 cases studied, they found that an average of 12.8 percent (!) of tank losses were due to artillery fire.  It's an interesting and short read.

Quick little addendum:

Now you can compare all of the shells on the same plot!  Science!  Interesting to see that the 203 shell is less dangerous at the same fragment density than the 152mm shell.  This is probably (definitely) because the model predicts the 203 mm shell only producing some 500 shells compared to the 1500 from the 152 mm shell.  That's not to say the 203 is less lethal - if any of those fragments hits anything, it's going to cause a hell of a lot of damage.
Currently working on calculating what I get compared to the test that I posted in the OP so many moons ago.

So I made a cool little blending function:

As the diameter reaches 5x the thickness, it is 100% like a cylindrical fragment, but at 3x the thickness, it has 50% of the cylindrical fragment and 50% of the random fragment's performance.
If we call P1(x) and P2(x) the two penetration functions, and B(x) the blending function, the actual penetration I'm doing is P(x) = P1(x)B(x) + P2(x){1-B(x)}.  The end result is a penetration table that looks like this:

The smaller fragments have somewhat worse performance compared to the pure cylindrical model, and the larger fragments have worse performance compared to the pure random model.  I'd say that's the best of both worlds, since we don't want to overpredict the performance of either fragment!
This generates a protection plot that looks like this:

Fits the middle ground!  Close in to the shell, where larger fragments dominate, the penetration is realistically limited.  Further out, where the smaller fragments dominate, the random model's lower performance starts to dominate.  In the middle, it's a mix.  Overall, the protection needed seems to match common sense, I hope!

I also pulled the maximum value from every radius and plotted this noisy graph.  This shows what you need to be safe at this fragmentation density under the "worst case" in that the densest fragmentation from the shell is pointed at you from any particular range.  It's noisy because of the combination of overlapping angles from the shell geometry and the grid size I used to plot the armor contours.

Man, I was implementing an equation that represents a random fragment shape when I discovered that, despite what my above plots say, the frag density is really 0.01 per square meter! That makes a difference in the ranges, if not the power of the fragments.  If you have a 100 square meter target in the above scenarios, you'll hit once per shell (on average) or once per 10 shells on a 10 square meter target, and so on.  After noticing this (embarrassing) gaffe, I went back and double checked all my formulas.  Everything seems in Ordnung. The problem was really with my plot titles saying "0.1" instead of whatever density I actually wanted and input upstream - now they are fairly dynamic, changing depending on what I put upstream  
So... a couple of correct graphs:

Here's our 152 mm shell - the shape is the same, but note that our BTR is protected at this (correct) density at only 30 meters instead of over 50 in the previous graph!  And now the random fragments:

And these results confused the hell out of me!  I went back and double checked everything again, output tons of variables and drove myself silly sorting through thousands of data points.  Why?  Well, take a look for yourself at the penetration tables for the different fragment types:

First, the "classic" cylindrical fragment!

And the random fragment.  Notice the problem?  These charts show that the penetration capability of the random fragment is better than the cylindrical fragment.  So I plotted a few more things, like the fragment weights and velocities to do a lookup manually.  Maybe the interpolation I did was wrong.  Well, nope!
At the data point I looked at, the fragment weight of interest was about 40 grams, and the velocity 1200 m/s - more or less.  So the above charts aren't so helpful at that.  Let's zoom in!


The random fragment actually is much worse for the smaller fragments.  Huzzah!  Mystery solved!  Also provides what I think the key to making a better fragmentation model.  Small fragments may entirely be random in shape, but the larger fragments will end up closer to the cylindrical shape.
(The staircase at 2 km/s is because I clip the data at that level so it's easier to read)
Though, now that I'm writing this, that probably could have been solved by looking at the color bar scales next to the plots.
So I propose the creation of a model where we look at the estimated cylindrical fragment, and compare the diameter to the height.  If the diameter is significantly larger than the height - say 3x to 5x, then we transition to the cylinder fragment model, while the smaller fragments use the random fragment model.  This could be blended using a logistic function or something to prevent ugly artifacts.
As a bonus, here's the 82mm mortar:


Note the much higher maximum penetration - this occurs very close in - within a meter or less of the shell.  Some of these oddities I think can be solved by the blending method I mentioned above.
That's it for tonight, I think.  Cheers, everyone!

Thanks!  Revisited the shells using the new formulation - analytical fragmentation patterns using the actual shape of the artillery shell.  One big caveat here - the formulation of the fragmentation is designed and programmed to be both 1) easy to deal with as data and 2) accurate particularly in the radial direction - the one we care most about!
So that caveat means that the fragmentation predicted on the up/down directions probably isn't super accurate - and you'll note that (due to how I coded the shape) - some shells see very little up/down spray.  That's simply because I haven't figured out a good robust way to account for the fragmentation of the upper and lower faces of the shell yet.
Also new and improved (TM) is the fragmentation penetration model - instead of assuming spherical fragments (because it's easy), I more correctly assume cylindrical fragments of the thickness of the shell at that location.  This affects the impact area - and greatly affects the penetration capability of certain shells.  This means that a 50 gram fragment from, say, a mortar, will actually be less dangerous than a similar 50 gram fragment from an artillery shell - since the shell fragment is thicker, it has a smaller presented area for penetration than the thin mortar bomb.
So, without further ado:
82mm O-832 mortar shell

This one has the correct shape now, too!  Drew it in Solidworks and grabbed some points on the perimeter to get it - looks good, I think!

The O-832 produces around 500 fragments of significant size, with few being larger than 50 grams.

The mortar bomb produces a blast pattern kinda like this - works very well for something that is meant to land vertically - maximum blast is directed up and away from the ground!  It's really cool to see this in action - since you'll see the artillery shells have a different pattern entirely!
152mm OF-530 artillery shell

Here's the wonderful 152mm OF-530 shell, which some of you may recognize as the shell I used in my explicit dynamics simulations:
Funnily enough, you can note that the blast and fragments are still primarily directed sideways from the simulation above on a 40mm plate, but to a lesser extent upwards compared to the mortar.

The fragments have much larger size compared to the mortar shell, with few being larger than 500 grams.

Comparing to the explicit dynamics simulation above, you can see that the primary direction of the fragments is indeed sideways.  You can imagine this pattern is better for a shell that will be landing at a much sharper angle compared to the mortar bomb.  As it rotates, the blast is still somewhat directed downrange, while there still is a sharp tick on the shallow side.  The odd-looking striations are caused by a combination of overlapping angles on the shell geometry and the size of the grid I used to plot the contours.
203mm OVF34 artillery shell

I had a hard time coming across good data on 203 mm artillery shells, let alone their shape or weight.  This is the best guess I could pull together, so if anyone has a good source for different types of Soviet artillery ammunition, I'd be grateful!

This shape of ammunition produces significantly fewer fragments - but note how huge they are!  I extended the fragment distribution up to 2 kilograms, and we still are seeing 5 fragments per shell bigger than that!

Which leads us to the penetration plot.  Up close, not even 100 mm of steel is going to reliably protect you from fragments from this monster.  Our BTR may not be safe out to 60 meters from these shells (with a 0 degree obliquity impact - angled armor does more than just increase LOS thickness when it comes to fragments, as best as I can tell).

Quick preview of what I've been working on over the weekend:


Refining the fragmentation pattern to be soundly based on the shape of the shell compared to the cylinder-based model from before.  Compare the above, 203mm, shell to:


An 82mm mortar shell.  It seems the larger shells produce somewhat smaller numbers of larger fragments, while the smaller ones with thin walls produce many smaller fragments.  I still have some work to do, including verifying that this behavior is correct.

So we can solve the THOR equations to figure out what kind of velocity a fragment needs to penetrate a certain thickness of armor:

As you can see, the heavier fragments (as expected) perform better at penetrating armor - requiring less velocity to do so.  As the armor gets thicker, the fragments begin to require prohibitively fast speeds to penetrate.  Typically on an artillery shell it seems the initial velocity is in the realm of 1.5 km/s.

Using the data generated for the angular dispersion plus some more to accommodate the shape of the shell, we can arrive at the fragmentation pattern for a shell travelling in the negative x direction.
The dip in the negative x direction comes from the nose of the shell obstructing some fragmentation, and the larger dip in the positive x direction is the same for the base - a more significant effect for the more significant blockage provided by the base of the shell.
This can all be combined together by some clever interpolation (good god it took a while to figure out how to massage the data to make that possible!).  If we select a fragmentation density - say 1 fragment per square meter, we can generate a contour plot showing us the thickness of armor required to generally have no perforations.

Note the axes are not the same scale - this is to provide a better visualization of the regions.  At this density, a single artillery shell is likely to perforate a BTR 12 times at ranges up to 7 meters.

If we set the criteria to only 1.2 perforations per artillery shell (on average), we can see that our BTR isn't safe even up to 20 meters away!

This can all be consolidated into a few lines showing the maximum distance that you're likely to penetrate a 1x1 meter target with 0.2, 0.4 ... 1.8 fragments per artillery shell.  The flat region at the top might be because I capped the maximum fragment size I analyzed.

THOR
So as not to clot this up with duplicate plots, I only grabbed the interesting ones from the THOR runs:

Here's the penetration velocity from a 5 g fragment according to THOR.  Not much at all, eh?  THOR, as previously mentioned, was the standard, as best as I can tell, for modeling armor protection.  Unfortunately, as I previous mentioned, it seems to have problems with fragment-like objects.  This is further reinforced by the surprising results that the Soviet Artillery Effects study showed, which as far as I can tell, old armor/artillery models used THOR.  I suspect the truth lies between R&I and THOR here.  THOR predicts the armor is pretty resistant to 5 gram fragments at ranges beyond 5 meters, while R&I predicts danger out to 20 to 30 meters.

If we step up to 10 gram fragments, shown above, we can see the density start to fall off.  It does so sharply.  If you refer to the probability curve I posted earlier, you can see that the probability of has a strong negative curvature to it, so the larger we go, we'll see much fewer fragments.

These 10 gram fragments are impressively dangerous, however.  THOR predicts these 10 gram fragments maintaining a velocity of 146 m/s after punching through 10mm of armor, at a density of 1.03 fragments per square meter.
Even under the conservative THOR model, our BTR gets perforated with 11 fragments of greater than 10 grams.  That's going to cause some damage - whether it's injuring crew members or passengers, or damaging equipment.
Unfortunately, this same barrage in CMBS presents absolutely zero identifiable damage to the BTR.  It's worth noting that all this data is probabilistic, but CM clearly doesn't reflect this data.  I'd say, from what I've shown here, at least light armored vehicles are more resistant in-game to artillery fire than they should.  Combine this with the reports that we've seen from the SAE as well as front-line combat in Ukraine, and I'd say there's a fairly strong case here.  I know these plots only show a single case of 12 shells, but it takes a while to write and generate them!  I've recorded observations from a number of tests, both in real games and purposeful tests, in addition to the one presented here, but I don't have good enough data to present more plots on those cases.
I leave tonight with this question: What else do we need to know here?  What more can I do to help us understand this?
Thanks everyone for helping in this thread, and I hope to see more discussion.

Recht & Ipson
So, the BTR-70 has 10mm armor at its thickest.  Seems artillery shell fragments can easily penetrate this!

Here's the maximum velocity of a 1 gram fragment as it travels from the blasts.  It can be seen that the fragments barely lose their velocity This can be used to calculate the velocity if a fragment impacts something.  Say... a 10mm thick plate of armor on a BTR.

So you can see the velocity of the fragment after penetrating a 10mm plate at any point in our artillery distribution.

We can combine this with the density of the fragments greater than a certain mass.  And, for the sake of thoroughness (if you can call it that haha), the same plots for a 5 gram fragment:

 

At the BTR's position, we have the following data points:
Density of fragments > 1 gram: 2.42 frags/m^2
Density of fragments > 5 grams: 1.49 frags/m^2
Penetration velocity of fragments > 1 gram: 98 m/s
Penetration velocity of fragments > 5 grams: 270 m/s
I showed earlier (the common knowledge) that heavier fragments are more deadly - and this is confirmed here (probably because I used the same model).  If we take the dimensions of a BTR-70 (7.5 m X 2.8 m X 2.3 m) and call the average cross section presented to the artillery shells here as the average between the front and side cross sections, we get about 12 square meters.
So this barrage hit our BTR with 29 fragments greater than 1 gram, which probably don't have enough energy to cause significant damage inside the vehicle.  It also hit with 17 fragments greater than 5 grams, which certainly have enough energy to cause some significant damage to whatever they hit.
According to Recht and Ipson's model.  Next post, I'll run it using THOR.