Artillery and marshes

[rocketman]

I looked in the manual I found nothing while searching the forum. It is my impression while playing "Eye of the Needle" (which to a large extent is one big marsh), that artillery rounds that land in marsh areas have a much smaller explosion and kicks up much less debris/shrapnel. Also seems harder for FO to spot. Is this modeled in the game? If it is, is that also true for other ground conditions such as deep snow (FI) and mud?

[A Canadian Cat]

I have no idea.  Do you think you are seeing reduced explosions in game in the marsh right now?  I don't recall noticing.

[kevinkin]

Good question. I would imagine rounds would get dampened in thick marsh or mud. But not air/tree bursts. The answer at least in part may be in the forum somewhere.

Kevin

[womble]

Pretty sure it's been established that the damage effects of arty are the same whether it lands in Marsh or on a concrete hardstanding. I can't see an engine that makes no distinction for damage purposes making a distinction for spotting purposes.

[Jim1954]

I don't know for certain about marshes but I am currently playing a RT battle that features a small river in it.

My 82mm mortar rounds hit the water and there isn't even a splash.

[rocketman]

I might run some tests to find out.

[Vanir Ausf B]

There is no difference in effects between dry ground and mud, but I don't think marsh or water tiles have been tested.

[rocketman]

I will give it a go and see what I come up with.

[Melchior]

I'm curious to know too because I could swear marshes dramatically decrease the effectiveness of artillery fire.

Conversely forests tend to be about the worst place to be in the game during a bombardment.

[rocketman]

I'm half-way through testing. Should post results later on today.

[rocketman]

This is the test I ran. Flat area about 200 m in diameter with water around it, so no one could run away. Two platoons, HQ:s, and snipers from a rifle company - all in all about 80 men distributed over this area. All HQ:s in bunkers so that no unit would be out of command. I had an 81mm mortar on pre-planned, heavy, maximum barrage (100 shells). I then used the exact same map, but substituted grass for marsh and then also with heavy marsh. Units in the exact same spots for all three maps, and barrage called to the exact same spot and the same area range. Ran the test 10 times for each map and it looks like any differences are within the margin of error. The explosions look much smaller on marsh and heavy marsh, but the effect seems to be the same.

 

I wonder if results would be different if units are up and running, that is that shrapnel is dispersed shorter ranges from marsh ground conditions. But I'm not sure how to test it both in a valid and reliable way.

[Bulletpoint]

I'm curious to know too because I could swear marshes dramatically decrease the effectiveness of artillery fire.

Conversely forests tend to be about the worst place to be in the game during a bombardment.

 

No, in fact forests offer good cover against artillery in this game. At least against 60mm mortars. Lethality cut to about 1/3.

[Baneman]

No, in fact forests offer good cover against artillery in this game. At least against 60mm mortars. Lethality cut to about 1/3.

 

I tend to agree that treebursts are under-modelled in CM ( although this is just an observation, I've not done any proper tests ).

[Bulletpoint]

I tend to agree that treebursts are under-modelled in CM ( although this is just an observation, I've not done any proper tests ).

 

Well, I've done some tests, and light forest offers a lot of protection against 60mm mortars.

 

I don't know why that is.

 

It could be because treebursts take point of explosion so high that soldiers on the ground are getting outside of lethality range.

 

Or it could be the trunks of the trees blocking fragments (probably by blocking LOS between point of impact and centre mass of the soldier).

 

Or it could be that forest tiles simply have built into them a high cover modifier bonus.

[womble]

Bulletpoint, did you do your tests on "Light Forest" tiles with trees sprouting out of them, or were the trees growing out of mown sward or flat dirt? Checking the effects of 60mm bombs in the two different settings would show whether it is the "terrain save" of Light Forest or the effect of the trees at least.

[Melchior]

Well, I've done some tests, and light forest offers a lot of protection against 60mm mortars.

 

I don't know why that is.

 

It could be because treebursts take point of explosion so high that soldiers on the ground are getting outside of lethality range.

 

Or it could be the trunks of the trees blocking fragments (probably by blocking LOS between point of impact and centre mass of the soldier).

 

Or it could be that forest tiles simply have built into them a high cover modifier bonus.

 

I'm under the impression that forests provide cover and protection from a lot of things but artillery is not one of them. The way forest bombardments have been described a forest seems to amplify the effects of artillery fire. Rounds going off in the canopies of trees become airbursting rounds, and trees exploded by fire tend to spray lethal wood splinters adding to the overall fragmentation. 

[kevinkin]

Rocketman's test reminded me of that poor N Korean guy executed via a pre-spotted 120 mm mortar round.

 

But anyway ... the test appears conclusive. I would imagine modeling artillery fuses is outside the scope of CM.

 

Kevin

[JasonC]

Tree splinter lethality is extremely overrated. The increased lethality of medium to heavy artillery in woods, vs infantry without overhead cover, comes pretty much entirely from raising the height at which the shell bursts, not from extra secondary projectiles. VT fuse artillery is more, not less, effective. Because it gets the extra height, gets the right amount of it, and doesn't intercept primary metal shell fragments with tree trunks. If you were picking a VT height for 60mm you'd pick around 5 meters, not 30.

With much lighter rounds, I would expect trees to do more to protect infantry, especially taller trees. A 60mm round is quite weak as artillery goes, and its effective blast radius is considerable smaller than the height of typical trees. The shells are simply going to explode so high if they do hit a tree, that the direct blast will do nothing to men on the ground. Yes there will still be primary metal shrapnel, but you don't get nearly as many shards big enough to inflict serious wounds from a 60mm as from say a 105mm shell. Tnen many of those will hit trees on their way toward a man on the ground, etc.

Edited July 24, 2015 by JasonC

[cool breeze]

What JasonC said is pretty much exactly what I was thinking about the matter  ( not that that lends any extra weight to it  .  

 

The test with the trees on grass vs trees on light forest vs open grass seems good.  I think the experiment would be better tho if the guys were in foxholes and the rounds be made bigger.  Like JasonC says the trees give too high of airburst with 60mm.  I think 105 120 or 150 would be better.  providing foxholes makes it so the airbursting nature matters more, the bigger rounds make the explosions more in range, and while JasonC is playing down the wood splinters I imagine they might help when its a big round sending a large amount of wood flying. 

[JasonC]

cool breeze - I can explain the wood part two ways, one a priori and one experimental.  The experimental first - go find the Mythbusters episode where they shot cannonballs through the side of a mocked up wooden ship era ship wall, with pigs on the other side as all the splinters went flying from the cannon hole.  Superficial scratches were all they found.  Of course the details are different, but the principle is not.  Small splinters of wood have very little mass, no sectional density to speak of, and lots of total area for air resistance to slow them down.  They are remarkably poor penetrators.  Much larger chunks if they hit straight like an arrow can indeed penetrate, but both are rare among fragments (enough size, and the orientation of the hit).

 

Compare the casing of the actual shell.  It is mild steel and blown into thousands of fragments, each hard enough to keep going through anything water-like it hits.  Some get too small to carry very far before slowing down to less than lethal velocities, and that's why it is much safer to stand far from a shell going off than near one.  But all of them start at lethal velocities and they are all hard enough to penetrate well.  Are they large enough to cause significant injury, and do they intersect a man in the target area, become the only variables.

 

The energy from the explosion of the shell is driving primary or secondary fragments.  Using secondary ones just means a worse material to use and lots of dissipated energy, spent tearing the tree apart to use its bits, etc.  Better if the same energy is in the shell fragments than in the tree fragments.  It is an illusion to think the explosion can be made more deadly by being spread into more physical material of worse composition.  

 

Even shrapnel - spherical caseshot filled with metal balls - is actually marginally *less* effective than the same shell weight carrying more HE instead of the ball, because just driving the fragments of the shell casing to higher velocity is more important.  But that's with perfect projectiles in terms of size and density and hardness, etc.  With crappy materials and crappy random shapes hitting at mostly crappy angles, obviously the effect isn't going to go *up*.

 

Does this mean first hand accounts of the danger of being shelled in trees are rot?  No, nothing like it, but the men who know that much don't need to understand all the physics of *why* it is dangerous.  The reality is the big difference is purely the airburst.  Hitting the deck even without other cover reduces the danger to a man from a ground burst artillery shell by as much as 90%.  But it doesn't provide *any* protection, really, against an airburst at around 1/2 the casualty radius of the shell, into the air.  You can get protection against airburst shells, but you need to e.g. hug the side of a foxhole with a steel helmet uppermost - to get protection comparable to just lying flat with no prepared position, against ground burst artillery shells.  The same foxhole with head below ground would provide protection against everything but a nearly direct hit, vs ground burst artillery fire.

 

If the tree heights are between 1/2 the casualty radius of the shells hitting those trees and the full casualty radius, you get that huge air burst benefit - up to 10 times vs prone people without foxholes - with only a minor drawback for some shell fragments intercepted by trees in the way, and some energy dissipated uselessly into flying bits of wood.  But raise the explosion height to 4 times the effective blast radius of the shell, and you'd have a complete "ceiling" or "dome" just protecting the guys on the ground by holding all the explosions so far away they can't hurt anything.

 

In reality you get a mix of those things, plus some proportion of ordinary ground impacts.  But the net effect is greater danger if the shells are big enough and the trees are low enough.  The men picked up on that net effect - the rest is fixation on the visually impressive etc.

[LukeFF]

Tree-burst grogs.

[Bulletpoint]

Bulletpoint, did you do your tests on "Light Forest" tiles with trees sprouting out of them, or were the trees growing out of mown sward or flat dirt? Checking the effects of 60mm bombs in the two different settings would show whether it is the "terrain save" of Light Forest or the effect of the trees at least.

 

Yes, I did the tests with light forest tiles with trees, so I would have to go back and re-test with and without the actual trees. Maybe I will go back and test some day when my curiosity overcomes my laziness

 

I have a feeling the results are due to a combination of some rounds detonating too high for 60mm to have much effect on ground level, and that trunks of trees are blocking some lines between impacts and troops.

[kevinkin]

I am shooting from the hip but I believe the tree burst effect (a form of airburst)  is more moral than physical on dug in troops. But in the west US troops had to keep moving and in the open they needed to deal with the physical effects as well (many non-killing injuries from stupid metal and wood splinters). On defense, weapons like mortars need to be above ground to fire so they are at risk more than the rifleman. Perhaps using trees was a way to produce an air burst effect with available flat trajectory fire with say heavy flak like 88s? Although the canopy absorbs lateral moving fragments, a lot of shell fragments are directed down toward the ground (but with less energy) than would otherwise occur in the open. Tree bursts have both moral and physical effects and I think are best employed in suppression fire to harass the enemy with non-lethal wounds and lack of sleep in muddy below ground foxholes. Catching moving troops above ground in a forest would require excellent observation and timing. Not impossible just tricky.   

 

Kevin

 

PS didn't the Band of Brothers have a tree burst scene in it towards the end of the series?

Edited July 31, 2015 by kevinkin

[Bulletpoint]

On defense, weapons like mortars need to be above ground to fire so they are at risk more than the rifleman. 

 

I'm pretty sure mortars work their best from a dug out pit or trench... If I'm not mistaken, that's why they were invented - trench warfare.

[kevinkin]

Sorry .. Yes, from trenches or foxholes  but without overhead cover that would just block the outgoing shell.

 

Kevin