Are trenches too effective?

[Redwolf]

Originally posted by JasonC:

On map means the individual fall of shot is being observed. They see whether each round is an "over" or an "under". (An under obscures the target, an over shows it in sillouette against the blast plume). And they also see whether it is off-line, in the direction of the target. They correct after every round. Off map is firing in battery, on a single angle from each of 4-6 mortars spaced side to side, then just dropping rounds down the tube as fast as they can reload.

Excellent points, Jason.

Seems I should have given the on-map accuracy more credit.

[imported_no_one]

I just dont see it.Even though I hate doing it,I just ran a simple test with 4 on map 81mm mortars(all with 40 rounds)firing direct,versus 4 on map 81mm mortars(all with 40 rounds)firing indirect with the help of a Coy HQ(with no bonuses),on a single trench apiece(IOW,2 enemy trenches total).All mortars were regular,as was the Coy HQ.I did everything I could to make the test unbiased,without allowing it to take forever.

They all looked pretty even to me,but I'm not wasting time counting each round.Suffice to say that it was not close enough to even warrant a closer inspection.

If someone would like to give a different,possibly less biased test a shot,I would like to know the results.

[ March 23, 2004, 06:39 PM: Message edited by: no_one ]

[JasonC]

Both of those are on map, both thus reflect individual corrections between each round. Try instead either of those, compared to an FO. The FO will put down the rounds in a much more scattered pattern. The on map will put down the round in thin lines along each direction of fire, with around a third of them clustered quite close to the aim point. The FO will cover the edges of the pattern better, and have greater side to side spread, with fewer rounds clustered immediately around the aim point.

"But isn't the HQ doing the same thing as the FO?" No. The FO is correcting 1-2 shots to within 50m then saying "fire for effect", after which no additional aiming or corrections take place.

[John Kettler]

To clarify my prior D-20 example, the weapon is the beginning-in-1955 progressive successor to the Russian WW II 152mm gun-howitzers. As such, it would be reasonable to assert that its effectiveness, round for round, would be higher than the WW II models, since one could argue both more powerful explosive fill and higher quality steel in the shell body. The basic concept still holds, though.

JasonC makes some excellent points. Things would be much simpler for players if they actually had the capabilities for pattern orientation and concentration real gunners had, not to mention more ammo types and fuze options . As it is, we seem to have a point target setting (Target) and an open sheaf (Target Wide) but no parallel sheaf, which by the way, is the standard firing pattern.

Conceptually, what the FO's really trying to do is put the mean point of impact (MPI) over the target by adjusting the spotting round/rounds where he wants them before calling in fire for effect (FFE). This is because one gun in a battery is used as the base gun upon which all the other guns in the battery align, yielding a predictable impact pattern, within statistical limits. Nor do we have the ability to call for a battery/battalion volley

or multiples thereof. Unless conducting surprise fire, the FO should be able to walk the aimpoint onto the target, then call for the number of rounds

and the rate of fire, as well as dictating shifts, lifts, and pauses. Artillery would be much more useful this way, rather than being an explosive spasm of short duration, and with the smoke/dust problem Treeburst155 describes, probably off target. If conducting an attack through open terrain with limited artillery resources, there's a lot to be said for slowly drizzling HE on the foe, since it keeps heads down, then going to high rate right before the troops are close enough to assault. Artillery fire delivered too soon or in the wrong way is artillery fire wasted.

Regards,

John Kettler

[Redleg Bob]

I think the real issue with indirect vs. trenches is not necessarily that FA is an inappropriate suppressive weapon against trench networks, but rather, that CMXX does not allow the player to select an appropriate munition and/or shell/fuze combination. Of course indirect fires aren't working -- HE Quick (A point detonating High Explosive round) is exactly the wrong shell to use! While I recognize that proximity fuzes were likely rare and expensive in WWII, I do not understand why an FO cannot select a time fuze instead, as these fuzes are much cheaper and easier to use. Further (and this is getting a little out on a limb) the best thing for hasty trenches IMHO is a 50/50 HE/WP mix (Shake and Bake) which destroys equipment, kills people, and completely obscures the trench itself.

But, to be honest, that may be a bit boring for people who aren't FA types and CMXX really is geared toward CO and Bn manuever tactics, which it models quite well.

[Carl Puppchen]

I am very glad that I started this thread. I learned a lot reading through the various comments. Here is what I think I learned:

- trenches are VERY effective against indirect fire, meaning off board artillery

- trenches have a relative weakness for on board HE fire and on board mortars

- firing at the trenches with a machine gun will suppress the infantry inside and limit their movement (unless they panic and run, which is just what you want to have happen)

- no one has really disagreed that trenches are perhaps too cheap in CMAK - since there is very little "good" cover in the desert scenarios such as heavy buildings, rubble, etc.. and open terrain means that the attacker usually has good LOS so a key hole defense is very hard to pull off - thus "relative" to other cover options trenches are hard to beat

- trenches in reverse slope defenses are VERY tough to beat, since you can't really bring on board mortars to bear and you can't suppress the defenders with MG's and direct HE (from relatively cheap onboard guns like the 65mm Italian IG) unless you drive a tank up over the crest, and this is a dangerous thing to do (especially when I am playing the Axis in the desert and you have junky british tanks with little / no HE)

Thanks again for all the tips.

[JasonC]

Redleg Bob - they not only didn't have lots of promixity, they didn't have lots of timed either. Nor lots of WP. What they had was stacks and stacks of plain HE, which when firing against trenches they used on fuse delay.

The undermodeling of CM HE effect against trenches stems from accurately treating shrapnel effects, but not really tracking blast proper, particularly the way it travels through cover.

In the real deal, the effective weapons against trenches were 150mm and larger HE. And the reason it was effective is it caved in trenches and buried people. The blast wave from buried HE does that, not the shrapnel from surface or air detonations. This was already true in WW I (when long static lines allowed much better ID of enemy positions, at least the forward ones).

To shelter from serious HE, defenders needed deep dugouts (or cellars in towns) - which risked blocked entrances but were not nearly as exposed as trenches. Airburst was not the answer, delay was, and the counter to that in turn was going deep underground.

[Redwolf]

Good summary, Carl.

I don't generally argues about the prices, I really wouldn't know what a correct price for a force catalysator like a trench is if I had to choose just one price independetly of inmates, terrain and time/weather.

However, one point I would like to repeat is that the trenches only appear that touch because the foxholes offer so enormously few benefit. The game should properly punish an attacker who have the defender time to dig in.

The 45% exposure foxholes do in no way fit in with a defense with 8% exposure trenches, minefields and major roadblocks, not to speak of concrete bunkers.

I think BFC should have added more defense settings, hastly, moderate and deliberate. In the latter case you get 8% exposure foxholes, you get every stationary AT weapon presighted and that is the only mode where you get bunkers and pillboxes. Moderate has 25% exposure in foxholes in the open and allows all the other stuff. In hasty you get the foxholes we have no but no trenches and no real AT mines.

[John Kettler]

Troops,

A properly dug trench should permit the troops to move about unhindered, so long as they keep their heads below parapet level. This seems to me a defect in current trench modeling, but as noted by several people, the foxholes need work, too, being more like field scrapes than the real deal. My kingdom for "Shake and Bake!" Also, I think it's much too easy to knock out bunkers with rather anemic weapons.

Regards,

John Kettler

[imported_no_one]

Originally posted by JasonC:

Redleg Bob - they not only didn't have lots of promixity, they didn't have lots of timed either. Nor lots of WP. What they had was stacks and stacks of plain HE, which when firing against trenches they used on fuse delay.

The undermodeling of CM HE effect against trenches stems from accurately treating shrapnel effects, but not really tracking blast proper, particularly the way it travels through cover.

In the real deal, the effective weapons against trenches were 150mm and larger HE. And the reason it was effective is it caved in trenches and buried people. The blast wave from buried HE does that, not the shrapnel from surface or air detonations. This was already true in WW I (when long static lines allowed much better ID of enemy positions, at least the forward ones).

To shelter from serious HE, defenders needed deep dugouts (or cellars in towns) - which risked blocked entrances but were not nearly as exposed as trenches. Airburst was not the answer, delay was, and the counter to that in turn was going deep underground.

In the real deal,dealing with large calibre indirect(150mm+) HE versus infantry in the open would equal surface or air detonations,for sharapnel effect?(Though you say these were more rare?)

150mm+ indirect versus trenches would equal fuse delay,right?So what does this mean for a round that falls 20m,more or less,from a trench line?Would the rounds still need to be as accurate as surface detonation rounds?What would be the effects of the dirt plume(dirt,rocks,shrapnel)falling back to earth,or down into trenches?How big would a dirt plume be from a 150mm,and up,indirect round of HE with a delayed fuse?

Also,what does FA and WP stand for?

[ March 24, 2004, 11:06 PM: Message edited by: no_one ]

[Carl Puppchen]

WP is white phosphorus

[JasonC]

FA is short for field artillery.

Surface detonations would be the normal thing when shooting at men above ground. That does have some blast effect but only quite close to where the round goes off, where it tends to be overkill. Fragments go out to a wider radius and are dangerous to anyone exposed. Just lying down can reduce exposure to fragments by a factor of 5 to 10. Uneven ground, any substantial cover to block long straight lines of flight, also help. When there is no obstruction and men are upright, they can be hurt at much longer distances than they can by blast. The fuse they use for this is called "quick", and basically goes off on impact.

Occasionally you'd see airbursts from proximity fuses (US late war) or timed fuses (everybody had them, but they were rare and easy to mess up). The other thing that can cause airbursts is tree cover, when fuse quick rounds strike branches high enough up, and explode before they hit the ground. These comments apply to all calibers, 50mm mortar up to 210mm howitzer.

But delay is used against dug in positions or against towns. Medium calibers (105 e.g.) certainly also used it in those cases, but it isn't as effective as the bigger stuff, 150mm and up. Because shells of modest size spread dangerous fragments fairly well, but have extremely limited actual blast.

A single 150mm shell will typically leave a crater around 15 feet across by about 5 feet deep. If one lands within a few meters of a trench it will obviously cave it in. Even 10m away it can easily make the nearest wall collapse into the rest of the trench. Each shell is displacing on the order of 20 tons of earth. Fragments can be intercepted by cover but the whole blast wave cannot. It just turns "cover" into the new "projectile". It dissipates only by spreading out far enough.

[tabpub]

A single 150mm shell will typically leave a crater around 15 feet across by about 5 feet deep. If one lands within a few meters of a trench it will obviously cave it in. Even 10m away it can easily make the nearest wall collapse into the rest of the trench. Each shell is displacing on the order of 20 tons of earth. Fragments can be intercepted by cover but the whole blast wave cannot. It just turns "cover" into the new "projectile". It dissipates only by spreading out far enough.

Jason, you are overstating the amount here a bit. A crater that size would be about half the amount of dirt you say (actually, about 13 tons). While still a lot, not nearly the 20 that you stated. I do agree that the concussion wave would cave in a lot of non-reinforced trenchs if the round landed in the proximity that you described in your example though, depending on the composition of the soil; etc. (which I don't think could be modelled in a game in the near future, though it would be nice..."Oh, crap, we have dug our trench in a peat field!"

[JasonC]

2.3 m radius, squared, 3.1416, 1.67 m deep, cup shape giving roughly 2/3rds of a square shape (less than square = 1, more than triangle = 0.5), in two dimensions, equals 12.3 cubic meters of earth, which would be 12.3 tons at the density of water. Dirt is considerable denser than water. The estimate is quite conservative. Typical dirt is 2.5 times the density of water which would give 31 metric tons.

If instead of a cup shaped 2/3rds, one uses a triangle 1/2, you get 6.92 cubic meters of earth, which still gives 17.3 metric tons. If one uses 2.5m radius and 3/4 shape and expresses the result in english unit tons, you'd get 51 tons. All results are on the order of 20 tons - order implies the right number of digits not the right decimal point - and 20 tons is on the conservative side. So no, I am not overstating the case.

For comparison, a 75mm shell typically leaves a crater only 1 foot deep and 2-3 feet across. There is no comparison. A 105mm shell typically leaves a crater 2 feet deep and 5 feet across, thus only about 1/6th as much earth moved as a 155mm shell. (Maybe less, because the shallower craters are less cup shaped, a bit closer to a triangle).

[Kanonier Reichmann]

Interesting discussion this. Suprisingly enough I've had a contrary experience in CMAK where less than 23 150mm artillery shells basically caused the rout of a platoon and a halfs worth of generally veteran German Rifle squads from their reasonably extensive trenchworks. I was fairly surprised (and pleased) at the outcome as it allowed me to renew my attempt to take the position with my few remaining troops. I may have been lucky perhaps by killing their leader early in the piece at a guess but it still turned out to be very effective.

Regards

Jim R.

[ March 25, 2004, 10:50 PM: Message edited by: Kanonier Reichmann ]

[JasonC]

KR - were they by any chance in woods? Airburst 150mm or larger is effective even against trenches. Which is why good players don't put their trench systems in the woods...

[cool breeze]

Just hopping to be impressed, but do you know the size of crater and weight of dirt for 210mm and other cool sizes?

[cool breeze]

Just hopping to be impressed, but do you know the size of crater and weight of dirt for 210mm and other cool sizes?

[tabpub]

Originally posted by JasonC:

2.3 m radius, squared, 3.1416, 1.67 m deep, cup shape giving roughly 2/3rds of a square shape (less than square = 1, more than triangle = 0.5), in two dimensions, equals 12.3 cubic meters of earth, which would be 12.3 tons at the density of water. Dirt is considerable denser than water. The estimate is quite conservative. Typical dirt is 2.5 times the density of water which would give 31 metric tons.

If instead of a cup shaped 2/3rds, one uses a triangle 1/2, you get 6.92 cubic meters of earth, which still gives 17.3 metric tons. If one uses 2.5m radius and 3/4 shape and expresses the result in english unit tons, you'd get 51 tons. All results are on the order of 20 tons - order implies the right number of digits not the right decimal point - and 20 tons is on the conservative side. So no, I am not overstating the case.

For comparison, a 75mm shell typically leaves a crater only 1 foot deep and 2-3 feet across. There is no comparison. A 105mm shell typically leaves a crater 2 feet deep and 5 feet across, thus only about 1/6th as much earth moved as a 155mm shell. (Maybe less, because the shallower craters are less cup shaped, a bit closer to a triangle).

Your example is a crater 15 feet in diameter by 5 feet deep. This results in an area of 281.25 cubic feet of dirt. This converts to 10.4 cubic yards. Now since a cubic yard is equivilent to 1.25 tons, the figure of 13 tons is correct. Now this would be for a hole that is straight down 5 feet in a diameter of 15 feet. As you did point out, craters are "cup shaped" and would be less than this amount. If anyone is interested, a sample site would be here http://www.rossjimson.com/information/

As they (and I) are in the business of moving stone and dirt, I would I have to disagree that the amount of 20 tons was a bit over the top. I don't have any idea what the water bit has to do with anything, as the weight of dirt is a known fact, and we don't have to extrapolate what it is. This is not a college experiment.

[Kanonier Reichmann]

Originally posted by JasonC:

KR - were they by any chance in woods? Airburst 150mm or larger is effective even against trenches. Which is why good players don't put their trench systems in the woods...

Nope, in the open on the brow of a hill. As I say, I was very pleasantly surprised.

Regards

Jim R.

[JasonC]

The "water bit" is that a metric ton is defined as the mass of a cubic meter of water. Your topsoil figure works out to around 1.5 times the density of water - which is less than the 2.5 times figure I've seen for earth generally, rather than topsoil in particular.

And a circle of radius 7.5 feet has an area of ~177 feet, times 5 feet of depth is ~884, or 32.7 cubic yards - if the sides were vertical, which they aren't. Your figure used the square of the radius (56.25 feet) but left out the factor of pi.

So vertical sides on your own density gives 40.875 tons. If the cup shape is 2/3rds in 2 dimensions, that would drop to 18 tons for the "bowl". If it is 3/4ths it would be 23 tons. Again 20 tons is the right order of magnitude.

[ March 26, 2004, 03:12 AM: Message edited by: JasonC ]

[Andrew Kulin]

I saw the above calculations and here's my two cents worth. The density of soil "particles" is typically 2.6 to 2.8 g/cm^3 (or 2.6 - 2.8 tonnes per m^3). (Water is 1.0 tonnes/m^3)

But soil is not 100% solid (otherwise it is called rock). There are void spaces in the soil structure that allow for air and/or water to be present in the soil. Use 30% void space as typical figure and your soil density drops by 30%. So use a figure in the 1.6 to 2.1 tonnes/m^3 range for typical soil density. That covers range of dry sands to wet till/hardpans.

If they are really serious about wargaming then I think BFC really needs to consider the effect of soil mechanics on combat in CMX2. :|)

Cheers

Andrew

[tabpub]

Originally posted by JasonC:

The "water bit" is that a metric ton is defined as the mass of a cubic meter of water. Your topsoil figure works out to around 1.5 times the density of water - which is less than the 2.5 times figure I've seen for earth generally, rather than topsoil in particular.

And a circle of radius 7.5 feet has an area of ~177 feet, times 5 feet of depth is ~884, or 32.7 cubic yards - if the sides were vertical, which they aren't. Your figure used the square of the radius (56.25 feet) but left out the factor of pi.

So vertical sides on your own density gives 40.875 tons. If the cup shape is 2/3rds in 2 dimensions, that would drop to 18 tons for the "bowl". If it is 3/4ths it would be 23 tons. Again 20 tons is the right order of magnitude.

I stand corrected. I was tired and still hungover and forgot the pi. Mopighhlk! <sound of foot inserted into mouth> I have come to rely on computers too much and have lost touch with the operation of a basic calculator and equations.

Back to the basic premise of the thread; no, I personally don't think that they are over effective, they "feel" about right.

[Redleg Bob]

JasonC,

Hate to be the guy to bring up old issues (i.e. not earth density), but I was wondering if you could help me out about this time fuze thing, as I obviously more of a recent vintage Redleg.

For all those in the forum who didn't know, the process nowadays for using a time fuze (in a manual environment) is quite simple. The Fire Direction Center, which calculates the firing solution for the guns, extracts a fuze setting off of the Graphical Fire Table (GFT) and sends it along with the other information to the guns. The Section Chief of the howitzer announces the firing data (e.g. HE, Time, Deflection 1300, Quadrant 475, Time 17.6) and the Ammo Chief selects a time fuze, uses a fuze setter to rotate the timer around to the correct value, and places the fuze on the round.

The Chief gives the command to fire, the pressure of the burning powder thrusts the rounds forward which begins the timer. When the time runs out the fuze explodes and causes the round to detonate.

From the time the gun receives the data, the round should be downrange in no more than 30 seconds.

Is this how it worked back in the day? Was it just a lack of fuzes, or has the technology changed quite a bit?

Thanks for the help!

Redleg Bob

P.S. The early post that elucidated the problem with point detonating fuzes is why US forces currently use VT or base ejecting (still in the air, only something comes out of the round like bomblets or burning felt wedges or whatever) projectiles in every indirect system from 60mm mortars on up in combat.

[John Kettler]

Here's something I found online while researching a different topic. It's the modern U.S. Army fire adjustment field manual, FM 6-30. I'll provide an excerpt shortly when I edit this, but for now, know that it is the book on procedures for adjusting fires and deciding what to fire at which target. Though obviously there are sections covering advanced technology, a lot of old school core procedure still remains.

http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/6-30/f630.htm

Here's the pertinent excerpt. Note particularly what it says about Shell HE Fuze Quick (default CM fuze unless VT is used) versus trenches.

Begin excerpt.

4-15. SHELL HE AND FUZES

Shell HE is the shell most often used by the observer in adjustment. It can be used with impact, time, or proximity (VT) fuzes for various effects.

a. Shell HE, Fuze Quick. Shell HE, fuze quick bursts on impact. It is used against the following:

Personnel standing.

Personnel prone on the ground.

Unarmored vehicles.

Light materiel.

Shell HE, fuze quick loses its effect if troops are in trenches, on uneven ground, in frame buildings, or on earthworks.

b. Shell HE, Fuze Delay. A 0.05-second delay can be set on the quick fuze to allow either ricochet fire or penetration (Figure 4-2). If the observer is firing into dense woods, against light earthworks or buildings, or against unarmored vehicles, he should use fuze delay for penetration. If a very high charge is fired at a small angle of impact on a very hard surface, a ricochet may occur, which results in low airbursts.

Figure 4-2. FUZE DELAY

c. Shell HE, Fuze Time. Shell HE, fuze tirne bursts in the air at a given time along the trajectory. An airburst is shown in Figure 4-3. It is used against the following:

Troops in the open.

Troops in trenches.

Troops in deep foxholes.

Troops in soft-skinned vehicles.

Fuze time must be adjusted to the proper height of burst unless the firing unit has corrections for nonstandard conditions computed. Therefore, consideration should be given to another shell-fuze combination if time is critical and airbursts are desired. Fuze time should never be used for high-angle missions.

Figure 4-3. FUZE TIME OR VT

d. Shell HE, Fuze Proximity. The VT (or proximity) fuze is a radio-activated fuze that detonates at a predetermined height of burst. A VT fuze provides the same effect as fuze time but does not have to be adjusted. It is an excellent fuze to fire with shell HE for surprise and unobserved fires. Also, it is very effective in high-angle fires. It should be used in missions conducted by an aerial observer when an airburst is desired. It is used against all targets that can be attacked with fuze time.

End excerpt.

Regards,

John Kettler

[ April 03, 2004, 01:50 AM: Message edited by: John Kettler ]