Bunkers Immune to Arty + Other Issues

[Philistine]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Claymore:

The historical record is clear on the effect of plunging fire on the concrete bunkers/strong points during WWII. Plunging naval gunnery during the Overlord and post-Overlord advance to Cherbourg DID NOT KNOCK OUT A SINGLE concrete bunker according to my references (available upon request).

CM modeling of artillery vs pillboxes DOES NOT require any fixes/patches.<HR></BLOCKQUOTE>

Could you post the reference? I don't have any idea whether a 14" naval gun would take out a pillbox or not, but I would imagine there would be a distinct difference in construction between a pillbox built to cover a beach, and thus expected to be hit w/ 8" to 14" guns and one built inland, where the biggest gun they will probably see is 8", and that infrequently.

The fact that BTS toned down the pillbox resistance suggests that there is some level of artillery fire which would damage them. (If the tweak was just to make them slightly vulnerable to 14" guns, it hardly seems worth it).

--Philistine

[Claymore]

Philistine posted "Could you post the reference? ...snip"

Gladly.

The best three (and at hand for exact title/ref) are:

"UTAH BEACH TO CHERBOURG, 6­27 JUNE 1944 (1947, facsimile reprint 1984, 1990, 1994; 213 pp., illustrations, maps, appendixes). CMH Pub 100-12, paper, GPO S/N

008-029-00129-2

A companion volume to Omaha Beachhead, this narrative rounds out the account of the landings at corps level and below and relates the course of VII Corps combat

operations which resulted in the capture of Cherbourg on 27 June 1944."

OMAHA BEACHHEAD (1945, facsimile reprint 1984, 1989, 1994; 167 pp., illustrations, maps, annexes). CMH Pub 100-11, paper, GPO S/N 008-029-00128-4, An operational account of a major phase of the campaign in Normandy between 6 and 13 June 1944.

ST-LO (1946, facsimile reprint 1984, 1994; 128 pp., illustrations, maps). CMH Pub 100-13, paper, GPO S/N 008-029-00127-6,

The operations of a single corps in the First Army's offensive during the first three weeks of July 1944 designed to deepen the lodgment area preparatory to the breakout

from Normandy.

Many more available upon request.

Cheers

[Guest aaronb]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Philistine:

Could you post the reference? I don't have any idea whether a 14" naval gun would take out a pillbox or not<HR></BLOCKQUOTE>

From http://www.warships1.com/Weapons/WNBR_14-45_mk7.htm ,

"Armor Penetration with 1,590 lbs. (721 kg) AP Shell

Range Side Armor Deck Armor

0 yards (0 m) 26.9" (668 mm) ---

10,000 yards (9,144 m) 15.6" (396 mm) 1.15" (29 mm)

15,000 yards (13,716 m) 13.2" (335 mm) 1.95" (50 mm)

20,000 yards (18,288 m) 11.2" (285 mm) 2.85" (73mm)

25,000 yards (22,860 m) 9.5" (241 mm) 4.00" (102 mm)

28,000 yards (25,603 m) N/A 4.75" (121 mm)

"

Basically, at point-blank range, you get 66cm of armour penetration.

After it has slowed down in the air (plunging fire at long range onto a deck - or pillbox), you get 12cm of armour penetration.

This is a british 14" gun - if we assume that the properties are close enough to other 14" guns, the top-penetration capability of an armour-piercing round is not enough to go through a bunker that is rated at 50cm of armour.

Repeated hits might gouge enough chunks out of the top to finally penetrate.

Even a 16" gun from this site maxes-out at about 18cm. Pillboxes are still safe.

[Brer Pinkey]

Could be my bad memory (@work so I can't check) but doesn't the bunker modeling have a stated value for the slit itself? I think the back door is a lower armour value also. Would the blast effect of a close miss directly in front or behind have a chance of penetrating these weaker areas? If this is not included in the abstraction might it be possible to model it as a 'hit weak point' strike?

And just a by the by, I had a 50% success ratio taking out two german pillboxes with a US infantry flamethrower from behind. I think the detailed hit information specifically said it hit the door.

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"What are we going to do tonight Brain?"

"The same thing we do every night Pinkey... We're going to take over Europe!"

[Jager 7]

Excellent research AaronB. At greater ranges the penetration advantage of NGF is negated and it all becomes plunging fire.

I have been inside a Japanese concrete bunker that had taken a direct hit on the outside of something large...don't know what. On the inside...not even a crack in the smooth wall or ceiling.

Out here..

[M Hofbauer]

Brer Pinkey,

taking bunkers out from the rear in close combat, be it with flamethrowers or simple infantry with grenades, isn't a special occurrance (as your post might suggest) but is SOP in CM. The problem is top-hits with large caliber arty.

otherwise, I agree with Jager7: excellent work Aaronb and Claymore! t seems you too follow the motto: "do want a game that works!"

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"Do want a game that works???" (CPT Stransky)

[Philistine]

<BLOCKQUOTE>quote:</font><HR>Originally posted by aaronb:

{snip}

"Armor Penetration with 1,590 lbs. (721 kg) AP Shell

Basically, at point-blank range, you get 66cm of armour penetration.

After it has slowed down in the air (plunging fire at long range onto a deck - or pillbox), you get 12cm of armour penetration.

This is a british 14" gun - if we assume that the properties are close enough to other 14" guns, the top-penetration capability of an armour-piercing round is not enough to go through a bunker that is rated at 50cm of armour.

Repeated hits might gouge enough chunks out of the top to finally penetrate.

Even a 16" gun from this site maxes-out at about 18cm. Pillboxes are still safe.

<HR></BLOCKQUOTE>

Interesting. I'd assume also that Naval (as well as regular) fire would use HE and not AP, and thus the actual armor penetration would be even less than you posted.

Thanks for the posts aaronb & Claymore.

--Philistine

[Olle Petersson]

<BLOCKQUOTE>quote:</font><HR>Originally posted by M Hofbauer:

Olle, ...

There is no adding-up effect of armor penetration or damage capability of single rounds...

Sorry but I think your opinion above is very silly. Any round, be it artillery or not, has a certain penetration performance, and based on that a certain chance of defeating the target's armor. The first round has as much or as little chance to destroy the target, as does the last round.<HR></BLOCKQUOTE>

This is correct but also very wrong.

Anybody knows that cutting down a tree with an axe can't be done with one stroke. Still it's possible to use axes to cut down trees, the secret is to strike several times at roughly the same spot.

There is no real difference with armour plates or concrete.

- Face hardened armour plate is pretty resistant to light hits, but loose a lot of it's performance once penetrated. T-34 frontal armour breaking in two pieces upon penetration wasn't uncommon, I've been told.

- Homogenious armour degrades less, but is also less persistent against "nagging" hits.

- Concrete is very brittle at the surface and even pistol shots cause external "flaking".

*** Begin examples: ***

In WW2 Norway had virtually no ATGs at all, but managed to knock out a couple of German tanks (PzKw I/II) using regular MMGs by shooting Looonnng bursts at the same spot. Each bullet cause some itsy bitsy tiny crack and denting of the armour, and the overall effect eventually results in a kill. More often than not the MG crew was killed by the tank before this happened though...

A more recent example is the A-10 Warthog. A round from it's 30mm cannon has no chance whatsoever to penetrate the armour of a modern MBT, still that gun can defeat any tank. It's the repeated hammering from a burst that does it.

Another civilian example is the jackhammer used to drill in stones and concrete. One blow from the hammer makes virtually no damage, and each blow is just as inefficient. Still it can make deep holes and penetrate thick slabs of concrete.

*** End examples ***

Anyway; it's not the performance of each round that changes, but each hit alters the performance of the target.

Usually this is not a big deal.

* Your example of rifle firing not being able to knock out a tank is fair, considering that it would take a lot more time and ammo than is available in a CM battle, plus that the tanks are better armoured than a PzKwI.

* Your example of a 37mm gun against a KT front armour; I suppose the n:th round, n probably being somewhere between 100 and 1000, hitting the same spot would penetrate, and by then most of the armour plate would be less resistant than originally. Still beyond the scope of CM.

* Multiple direct hits on a pillbox would degrade it's armour. How much is up to what weapon is used, how the fuse is set, where the hits are relative to each other, and so on.

If using 14" guns with the purpose of taking out pillboxes, the fuses will be set at a slight delay to allow the round to penetrate the surface before detonating. This would create a crater in the roof. If another round hits that crater, that crater will be deeper. Repeat until pillbox is knocked out... If it takes 3, 5 or 7 hits I don't know, but each hit has some effect.

This can be within the scope of CM.

* The issue of face hardened armour applies mostly to the Soviet stuff, and is thus definately within the scope of CM2.

A comment to Claymore about the issue of bunkers not destroyed with prep fire:

This was what in CM is referred to as a "Target wide" map fire. So there can't have been that many direct hits on any specific pillbox. Try in CM to place a wooden bunker in each corner of a square, about 100m a side, and then call for a "target wide" 105mm mission to the centre of the square and watch how many bunkers get blasted...

I can't recall any photographs from D-day showing the bunkers surrounded with craters from near misses, as would have been the result of directly aimed fire.

I think I've made myself a bit more clear now.

[IntelWeenie]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Olle Petersson:

* Multiple direct hits on a pillbox would degrade it's armour. How much is up to what weapon is used, how the fuse is set, where the hits are relative to each other, and so on.

If using 14" guns with the purpose of taking out pillboxes, the fuses will be set at a slight delay to allow the round to penetrate the surface before detonating. This would create a crater in the roof. If another round hits that crater, that crater will be deeper. Repeat until pillbox is knocked out... If it takes 3, 5 or 7 hits I don't know, but each hit has some effect.

This can be within the scope of CM.<HR></BLOCKQUOTE>

But it currently isn't. Yes, buildings in CM are modeled something along these lines, but they aren't armored.

You do have a point about cumulative effect, but IMHO it would take more than a dozen or so (point detonating HE) shells fired to do destroy a typical Atlantic Wall bunker by "chipping".

<BLOCKQUOTE>quote:</font><HR>A comment to Claymore about the issue of bunkers not destroyed with prep fire:

This was what in CM is referred to as a "Target wide" map fire. So there can't have been that many direct hits on any specific pillbox. Try in CM to place a wooden bunker in each corner of a square, about 100m a side, and then call for a "target wide" 105mm mission to the centre of the square and watch how many bunkers get blasted...

I can't recall any photographs from D-day showing the bunkers surrounded with craters from near misses, as would have been the result of directly aimed fire.

<HR></BLOCKQUOTE>

Again, prep fires such as you're talking about are well beyond the scope of CM. Guns this size are almost never used in such close proximity to one's own troops because of the extreme danger of 'shorts'. Remember, the battlewagons usually were firing at distances of 10-25 miles (16-40 Km)!

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Canada: Where men were men, unless they were horses.

-Dudley Do-right

[Olle Petersson]

<BLOCKQUOTE>quote:</font><HR>Originally posted by IntelWeenie:

You do have a point about cumulative effect, but IMHO it would take more than a dozen or so (point detonating HE) shells fired to do destroy a typical Atlantic Wall bunker by "chipping".<HR></BLOCKQUOTE>

But as someone else noted; the pillboxes in CM are not "typical Atlantic wall bunkers", but inland pillboxes designed to take some less than infinite pounding from 20cm guns or less.

<BLOCKQUOTE>quote:</font><HR>Again, prep fires such as you're talking about are well beyond the scope of CM.<HR></BLOCKQUOTE>

Of course. The only reason I brought it up was in reply to Claymore's ranting about it's inefficiency.

In CM (version 1.05) there are a couple of ways to knock out pillboxes:

1) HE rounds through the slit. (Difficult to hit.)

2) Spigot mortar direct hit. (Fairly short range and it may take a couple of hits to knock out the box.)

3) Flame throwers. (Can attack from any angle, but only at short range.)

4) Rear door penetrations. (Much less effective than firing slit penetrations, but also less dangerous to the attacker.)

Only the Spigot actually have a real chance of destroying the bunker (by internal combustion). The other merely destroys the inventory or force the crew to leave.

I need to compare data of the Spigot and 14" shells to find out which has the most blast in CM, but judging by the craters there is no doubt...

Well within the scope of CM is also to bring up a couple of big (>10cm) guns (field guns or howitzers) to shoot directly at the pillbox from any convenient direction, read "the sides", preferrably using HC but more likely HE. 50+ direct hits from these should result in something else than "hit, no significant damage". A slow and ineffective way, granted, but still plausible. This is currently not possible in CM.

As for buildings in CM. These provide excellent HE protection for infantry. Even when using direct fired HE from tank guns or howitzers the building usually collapse before the occupants. This also seems ahistorical, since direct fired HE, aimed at windows and other openings, usually wipe out almost anything inside but leave the house standing. I use DF HE against enemies in buildings a lot, but still has never seen a wipeout from one "penetrating" round. When my infantry is attacked in the same manner it takes about one casualty per five HE shells fired, way too low.

As I see it, the reason for this thread to come up in the first place was for me the question; If 14" guns can't destroy a pillbox, then what can?

Cheers

Olle

[Claymore]

Ollie stated:

"The only reason I brought it up was in reply to Claymore's ranting about it's inefficiency"

me rant? hee hee hee HAW HAW HAW

I stand by the historical record. When faced with a pillbox that could not reduced with infantry (for numerous reasons) the Amis typically called in 105 M4s. Lacking that they used whatever tank they had handy. I have yet to read in any After Action Report (AARs) of any towed AT/Infantry gun used in the same manner. I would hazard that the unlimbering time and the unprotected nature of a field piece precluded them being used in such a manner. I am sure that the Russians used them in this manner however.

E.g. AARs of the 38th Cavalry Recon Squadron from Sept/44 - May/45.

The 38th Cavalry faced many Jerries in situations modeled exactly in CM, typically a company of infantry with an attached platoon of tanks and/or tank destroyers. The tanks would lay direct fire on the front of the pillbox both suppressing return fire and eventually knocking out the pillbox. If you read the AARs note that the 105 M4 was called an Assault Gun by the Americans.

Also,

"A comment to Claymore about the issue of bunkers not destroyed with prep fire:

This was what in CM is referred to as a "Target wide" map fire. So there can't have been that many direct hits on any specific pillbox. Try in CM to place a wooden bunker in each corner of a square, about 100m a side, and then call for a "target wide" 105mm mission to the centre of the square and watch how many bunkers get blasted...I can't recall any photographs from D-day showing the bunkers surrounded with craters from near misses, as would have been the result of directly aimed fire."

I don't have the American Forces in Action "UTAH BEACH TO CHERBOURG, 6­27 JUNE 1944" on my desk today. If I did I could scan a photograph of the forts at Crisbeq (very poor spelling attempt) showing craters from naval gunnery. The craters are on the same order of size as the pillboxes themselves although the gunnery did not knock them out. From memory I would say the top lip was at least 10m across. Let me bring my book from home tomorrow and scan the photograph. Send me your email address and I will post the photo to you.

or

If someone give me instructions on how to post photos to the CM forum, I will do so here.

The forts were in direct LOS of the Utah beach and targeted DIRECTLY by naval vessels. It doesn't say where the FOs were when this was happening. Since it is not part of the written record I will not guess where they were.

[Ataru *~]

Remember, the craters of the 14 inch shells in CM are about 4 times the size of the pillboxes; again, they're no coastal bunkers.

BTW, still looking for an explanation on the Flamethrowers.

Ataru

[PzKpfw 1]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Olle Petersson:

Of course. The only reason I brought it up was in reply to Claymore's ranting about it's inefficiency.

In CM (version 1.05) there are a couple of ways to knock out pillboxes:

1) HE rounds through the slit. (Difficult to hit.)

Cheers

Olle<HR></BLOCKQUOTE>

Uber Stuarts can get multiple slit hits at over 400ms while going 30mph, just ask Bastables what 2 Stuarts did to my poor 88mm bunker in 60 secs while drag raceing up a road .

Least my Sniper exacted some revenge as 1 of Basta's tank jockey's stuck his head to far out the hatch .

Regards, John Waters

------------

"Everyone is sick of the war, except those lunatics at Military HQ".

[This message has been edited by PzKpfw 1 (edited 09-07-2000).]

[IntelWeenie]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Olle Petersson:

But as someone else noted; the pillboxes in CM are not "typical Atlantic wall bunkers", but inland pillboxes designed to take some less than infinite pounding from 20cm guns or less.<HR></BLOCKQUOTE>

Then why are we debating the 14" guns' effectiveness? (sigh)

If we consider pillboxes to only be 'lesser' Westwall-type or other fortifications, then we should only concern ourselves with the weapons the allies used on those structures. Most accounts I have read stated that bombardment by 105-203mm arty was typically ineffective against the Westwall's concrete emplacements. Why? Because they were designed to withstand such bombardment. So, they had to be taken out the old-fashioned way: by the PBI (Poor Bloody Infantry).

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Canada: Where men were men, unless they were horses.

-Dudley Do-right

[Lee]

I think at this point we need some comment from Steve or Charles.

Just how thick is the concrete in these pillboxes? Should the

walls be able to withstand a direct hit or near miss by really big

artillery? And even if the concrete walls themselves could take

the punishment, could the crew inside live through the blast wave

if the shell were to hit near the viewing slit side of the pillbox,

thus giving the blast direct access to them?

Now, we're talking big artillery/rockets here only, not mortars and

light artillery.

[Ataru *~]

The game's physics shouldn't change depending on what happened or didn't happen; they should be based entirely on what *could* have happened. And they are... so why make an exception here? That is, IF the penetration values are actually wrong. Better than pretending the game's pillboxes are monstrous coastal bunkers.

This isn't an engine wrecking issue; if something is wrong it could probably be changed with a few keystrokes, and thus there's no harm in mentioning it.

Ataru

[Brer Pinkey]

hrrmm

<BLOCKQUOTE>quote:</font><HR>

taking bunkers out from the rear in close combat, be it with flamethrowers or simple infantry with grenades, isn't a special occurrance (as your post might suggest) but is SOP in CM. The problem is top-hits with large caliber arty.<HR></BLOCKQUOTE>

No. I checked. Yesss, the SOP for reducing a bunker is close assault etc... My previously unclear question is: Are the door and/or firing slit of a concrete bunker, as modeled in CM, modeled in such a way so that a sufficiantly large & close area of effect blast is able to penetrate either of them and cause non-negligable damage to a concrete bunker? Hmmm?

------------------

"What are we going to do tonight Brain?"

"The same thing we do every night Pinkey... We're going to take over Europe!"

[JoshK]

Caution: From memory only.

From The Good War, a great oral history btw.

An infantry commander's account of facing the west wall. His unit's advance was totally stopped, so SP 155mm was called in. The SPA drove up to the ridge overlooking the bunkers. They lined up a DF shot and had a first round hit.

The gunner told the infantry officer that he took out the bunker, yet the infantry officer pointed out that it was structurally unaffected.

The gunner basically said "trust me on this one" What happened is that the explosion on the face of the bunker caused overpressure that killed or incapacitated the entire crew.

Later on in this account the infantry officer got to pull the lanyard himself. He seemed to get quite a kick out of it.