The Titanium Bunker

[Redwolf]

As for data, one 75mm AP round could do between 600 and 1000mm of concrete:

http://books.google.com/books?id=CqrzT-bAUioC&pg=PA30&lpg=PA30&dq=%22ap%22+concrete+penetration+%2275mm%22&source=bl&ots=_Mktaeu1qk&sig=Jv8wmC64wCQruuCLCiG16W4uaNM&hl=en&sa=X&ei=9RzwUND0IM7O0QHL64DgDg&ved=0CC4Q6AEwAA#v=onepage&q=%22ap%22%20concrete%20penetration%20%2275mm%22&f=false

[A Canadian Cat]

Which is to say that I think this bunker should be VERY hard to take out, but not quite this hard.

Did anything change in CMFI or in 2.0 to make bunkers harder to knock out?

I ask because a while back I started the blue and grey campaign and the first two battles are on the beach and include several bunkers (or was it just the first battle). Anyway, they were no cake walk but they were not very hard to destroy. I destroyed them all, mostly with Shermans from the beach. There was one that proved tougher and since there was no Sherman that could get to it I used engineers and their demo charges to blast it. I certainly did not have an experience like this with any of those bunkers.

[c3k]

A save turn where the Sherman is blazing away, and has been for a turn or two, would be good to look into. C3K... maybe you can volunteer to check it out?

Steve

Oh, look! I just volunteered to check it out.

Okay, LiveNoMore, please PM me a savegame. I'll run some tests on this bunker resistance. (MikeyD, PM as well, please, so we don't duplicate one another.)

Ken

PS - The assumption that the inner walls are bare concrete and would allow ricochets is not something to which I subscribe. The German army had a lot of WWI vets. They knew a thing or two about how to survive artillery barrages. Part of that got transferred to the training manuals. Lining the INSIDE walls with sandbags (particularly the back wall and around the apertures) would greatly reduce any ricochet effect.

[ASL Veteran]

As for data, one 75mm AP round could do between 600 and 1000mm of concrete:

http://books.google.com/books?id=CqrzT-bAUioC&pg=PA30&lpg=PA30&dq=%22ap%22+concrete+penetration+%2275mm%22&source=bl&ots=_Mktaeu1qk&sig=Jv8wmC64wCQruuCLCiG16W4uaNM&hl=en&sa=X&ei=9RzwUND0IM7O0QHL64DgDg&ved=0CC4Q6AEwAA#v=onepage&q=%22ap%22%20concrete%20penetration%20%2275mm%22&f=false

Bunkers aren't made out of just regular poured concrete - you know that right? There are layers of steel reinforcing among other things within the concrete. Many small concrete bunkers begin life as a steel shell.

[akd]

Oh, look! I just volunteered to check it out.

Okay, LiveNoMore, please PM me a savegame. I'll run some tests on this bunker resistance. (MikeyD, PM as well, please, so we don't duplicate one another.)

Ken

PS - The assumption that the inner walls are bare concrete and would allow ricochets is not something to which I subscribe. The German army had a lot of WWI vets. They knew a thing or two about how to survive artillery barrages. Part of that got transferred to the training manuals. Lining the INSIDE walls with sandbags (particularly the back wall and around the apertures) would greatly reduce any ricochet effect.

Ken, please PM me.

[slysniper]

It is a good point to see how bunkers are doing again. I have ran no test for them recently. But I was designing a scenario with MG bunkers concrete, and found them great vs. infantry fire from the front. But still found them losing crewman to small mortar rounds. Which has always been their weak point. So instead of wasting that tank ammo, , just hit the things with 45 to 81 mm mortar fire and they die too easy still from what I see.

Other than that, they play pretty realistic from what I have seen.

[Redwolf]

Bunkers aren't made out of just regular poured concrete - you know that right? There are layers of steel reinforcing among other things within the concrete. Many small concrete bunkers begin life as a steel shell.

I know how concrete looks from the inside. Nothing is "just concrete" unless you use it for weight or something.

The AP shell shouldn't have extra difficulties with some extra layer of steel.

[MikeyD]

I just reran my little test swapping out the Shermans for Priests and their nice 95 pound HE artillery rounds. Good if you want the occupants to immediately panic, maybe if you're lucky kill most of them and perhaps eventually get them to abandon the bunker. but I still can't 'KO' the darned thing.

[akd]

HE will just burst on the exterior. Hit it from the rear with AP/HEAT or demo charge it. If you want bunkers that can be (predictably) KO'd by direct fire from the front, use the wood type.

Remember this is a generic stand-in for any number of very well-protected bunkers, including bunkers buried partially under several feet of earth. Often the only option to take out these bunkers was to maneuver out of their fields of fire, close and neutralize with demolitions, flame weapons or earth moving. It is actually fairly generous to allow them to be KO'd so easily with a rear aspect hit.

Suppression and morale state not impeding the function of the bunker crew is definitely a problem, but is not specific to bunkers (AFVs have same problem). Also note that there may be some bugs here that make bunkers either too vulnerable or too invulnerable under certain circumstances.

[YankeeDog]

HE will just burst on the exterior. Hit it from the rear with AP/HEAT or demo charge it. If you want bunkers that can be (predictably) KO'd by direct fire from the front, use the wood type.

I don't disagree with you at typical combat ranges (hundreds of meters or more), but at <50m, from a dead-on frontal aspect, it seems to me an HE shell through the firing slit would be fairly achievable. Hitting a ~.2m x 2m slit at 500m is really frickin' hard. Hitting same at 50m, not so much. Maybe not something that could be done reliably on the first shot, to be sure, but within a half dozen tries or so, I should think.

One tactic that wast used in dealing with both German concrete bunkers in the ETO and Japanese bunkers in the PTO was to suppress the occupants and force them away from the firing slit with small arms fire, and assign some lucky sod sneak up and try to fire a bazooka round through the firing slit. Obviously a high risk maneuver, but apparently successful often enough that they kept trying it and training the technique. If this tactic worked with a bazooka, and considering that a tank main gun is far more accurate than a bazooka, then I should think it would work with a tank.

I suspect the reason you don't hear much about tanks KOing bunkers frontally from point-blank range is that moving a tank up that close to the front of a bunker would usually be *really* dangerous, as even MG bunkers were usually protected by enfilading fire from AT assets, and the approaches to the bunker would often be covered with mines, tank ditches, etc. Bunkers were also often carefully sited to take advantage of natural terrain so that armor *couldn't* just drive right up to them.

But if a tank does actually manage to saunter up to hand-shaking distance with a bunker, then I don't see how even the a very well-made bunker survives very long.

[LiveNoMore]

@akd; I have some of the saved game turns dealing with this. Don't know how to get them to you though.

[akd]

I don't disagree with you at typical combat ranges (hundreds of meters or more), but at <50m, from a dead-on frontal aspect, it seems to me an HE shell through the firing slit would be fairly achievable. Hitting a ~.2m x 2m slit at 500m is really frickin' hard. Hitting same at 50m, not so much. Maybe not something that could be done reliably on the first shot, to be sure, but within a half dozen tries or so, I should think.

This falls back to the aiming for vulnerable points discussion of old. Remember the AI aims center of mass of the exposed area of a target vehicle/bunker. By moving extremely close, you reduce dispersion to zero and ensure that every shot hits the same point. If this coincides with an invulnerable area, as it may under some circumstances with bunkers, your are S.O.L. (just as you may be with a Tiger). Move the tank back a couple hundred meters and you should see more spread of hits across the front of the bunker.

@akd; I have some of the saved game turns dealing with this. Don't know how to get them to you though.

PM me and I will give you my e-mail. Or use Dropbox to upload a save. I am most interested in a save showing the Sherman fail to KO the bunker from behind.

[YankeeDog]

This falls back to the aiming for vulnerable points discussion of old. Remember the AI aims center of mass of the exposed area of a target vehicle/bunker. By moving extremely close, you reduce dispersion to zero and ensure that every shot hits the same point. If this coincides with an invulnerable area, as it may under some circumstances with bunkers, your are S.O.L. (just as you may be with a Tiger). Move the tank back a couple hundred meters and you should see more spread of hits across the front of the bunker.

Interesting point. It may well be that the CMx2 engine has reached the point of refinement that the "Achilles Heel" of certain types of units, such as concrete bunkers, needs to be taken into account in some way. IHMO, it's actually a good sign that the game engine has reached a point of refinement that its worthwhile to have a serious discussion about things like this.

It seems a reasonable conclusion that the aiming routine for tank gunners should in some way "know" that a concrete bunker is more or less invulnerable to main gun fire everywhere but the firing slit, and therefore aim for the firing slit when the range & aspect makes this a practical target.

[ASL Veteran]

"Bunker 24, known as a “silo” bunker by the Americans was a fighting bunker of the general construction plan Type SK/6a or Kampfbunker. Built in 1938, the same year as Bunker 27, it was slightly smaller than the troop shelter, but boasted an armored machine gun turret on the roof. Protected by walls 2 meters thick, it could accommodate a crew of nine, though more could fit inside if the situation warranted. Impregnable to even direct hits from the largest shells then in use, it suffered from the same weakness as Bunker 27 in that its northwestern orientation also left it vulnerable to an attack from the sides and rear where its main entrance lay.

Riding atop the tanks in order to avoid bouncing betty anti personnel mines the Americans quickly reached bunker 24 and 25, a smaller troop shelter 100 meters to the southwest and began to methodically assault both structures. One of the tanks was equipped with a bulldozer blade, which it used to push dirt over bunker 24s firing embrasures and exits, while infantrymen placed shaped charges on top. After several of these charges were detonated, two Germans rushed out of the exit and surrendered.

Although bunker 25 fell quickly to a team of infantrymen and combat engineers supported by one of the tanks, bunker 24 proved to be a more difficult challenge. While engaged in placing shaped charges on bunker 24, heavy German artillery and mortar fire as well as small arms fire (probably from the positions of the nearby 3rd platoon) forced the men of company B to withdraw to their line of departure at bunker 27 to seek shelter after they had suffered heavy losses.

While the infantry pulled back to safety, the four tanks from Company A, 709th Tank Battalion continued the attack against Bunker 24, and it’s adjacent trenchline with cannon and machine gun fire. One Sherman was soon knocked out by a direct hit caused by the intense German artillery fire. The bulldozer tank attempted to use it’s blade to bury the occupants of the bunker alive, but it slipped over the edge of the ice covered embankment at the rear exit and became wedged against the door.

The crew’s frantic efforts to place the engine in reverse and back out of their predicament proved unsuccessful. Undeterred, the Gis inside the dozer tank decided to do as much damage to the bunker as possible and fired all of their ammunition, about seventy rounds of 75mm high explosive and white phosphorus against the armored door, scarcely ten feet away. While they were eventually forced to abandon their tank, the crew at least could boast that “We didn’t get in, but the Krauts didn’t get out.”

When Wegner arrived at Bunker 24 at 2000 hours, he noticed that there were ten sacks of American high explosives and shaped charges stacked along the entrance side of the bunker. He couldn’t help but notice the dozer tank partially blocking the right entrance door and saw that the outer walls of the bunker were heavily damaged. On the steps by the left entrance lay rubble and he noticed metal reinforcing rods sticking out of the concrete at the corner that completely blocked the entrance. Near the right entrance lay two seriously wounded soldiers who had just been brought out of the bunker. A step or two inside the entrance he stumbled on two bodies that had just been laid near the door. Inside the right side of the bunker, Wegner saw a dim light burning and noticed several soldiers engaged in caring for the wounded and clearing out the interior. In his words, the interior of the bunker presented a tragic sight. From the roof hung steel reinforcing rods and metal strips. The interior walls of the bunker were also cracked and shattered, evidence of the American’s use of the new “beehive” shaped charges. Bits of concrete and equipment lay upon the dead and wounded. Wegner found the body of Oberleutnant Kold underneath that of another dead Volksgrenadier. When he lifted Kolb’s body, the smell of phosphorus filled the air, already chokingly thick with the smell of gunpowder and concrete dust. Except for skin abrasions and bruises, none of the dead or wounded had any marks on them; evidently they were killed or injured by blast overpressure and concussion.

Another survivor of Bunker 24 was Unteroffizier Kurt Klein, who had accompanied Kolb as NCO in charge of the company’s command group. Klein was found covered in blood and babbling incoherently, evidently having suffered a mental breakdown from the strain of being trapped in the bunker while artillery, shaped charges, and tank shells were detonated within feet of him and the others. It was Klein who had found the body of his best friend, Heinz Kolb and though wounded himself, had tried to shield the body from further harm. In addition to his psychiatric injuries, Klein also suffered from phosphorus burns on his face and neck that required extensive treatment.

After receiving first aid, Klein was evacuated to a military hospital in Plauen, where he was beset by nightmares and crying fits. Shortly thereafter he was moved to an Army mental hospital in Rodewisch, where one doctor wanted to use shock therapy to treat his depression. A kindly staff doctor, who also had a son in the Wehrmacht who was Klein’s age, took a liking to him and had him put to work in the hospital telephone exchange as part of his therapy. Here he worked as an operator until the end of the war, when he was taken prisoner. Classified as a combatant, Klein was forced to walk to the nearest POW camp while still dressed in his pajamas."

That passage compliments of "Victory was Beyond Their Grasp: with the 272nd Volksgrenadier Division from the Hurtgen Forest to the Heart of the Reich."

If only those foolish Americans would have known that just one or two AP rounds from any of those four tanks could have taken care of bunker 24 in a few seconds. They could have left the engineers with their demo charges behind and a lot of lives could have been saved since they wouldn't have been hit by that artillery fire. It should also be noted that the tanks were not subjected to any AT fire and had the freedom to drive around at will.

Here is an example of that bunker type that I found after a quick search

http://en.tracesofwar.com/article/7877/Westwall---Regelbau-SK-Bunker-Aachen-Forest.htm

[sburke]

I knew I'd heard that story, but thought maybe it was in Bloody Aachen. Victory was Beyond Their Grasp is a great read.

[Michael Emrys]

...Priests and their nice 95 pound HE artillery rounds.

Huh? Last time I checked, a 105 mm HE shell weighed 32 lbs. Are you talking about something else?

Michael

[John Kettler]

Michael Emrys,

I fear this is a case of mental files getting crossed. I suspect this is where the 95 lb. shell weight originated. The M12 GMC was so potent a bunker and hardened position destroyer the German commander at Aachen, Germany said it was unfair.

http://en.wikipedia.org/wiki/M12_Gun_Motor_Carriage

Regards,

John Kettler

[LiveNoMore]

The Titanium Bunker finally went down thanks to two determined bazooka teams.

Uploaded with ImageShack.us] Uploaded with ImageShack.us

[akd]

Thanks for the saves LiveNoMore. The issue with the Sherman failing to take the bunker out from the rear appears to be slope effect. The Sherman's angle to the side combined with its elevation above the bunker makes the aim point effectively impervious to AP, so the TacAI just fires HE. If the Sherman moved around more behind the bunker, it would fire AP and penetrate.

[Battlefront.com]

Ah, that explains the failure from the rear attack. Not necessarily the outcome one would expect, but technically it's not a bug. The attack on the front, though, is still something to look into.

Steve

[Michael Emrys]

I fear this is a case of mental files getting crossed. I suspect this is where the 95 lb. shell weight originated. The M12 GMC was so potent a bunker and hardened position destroyer the German commander at Aachen, Germany said it was unfair.

That thought crossed my mind as well. But I think the 95 lbs may be the weight for the complete round, propellant and case as well as the shell.

Michael

[John Kettler]

Michael Emrys,

I fear your long run of correctness has at last been broken. For one, the 155mm gun fires a separate bagged charge, therefore uses no cartridge case. For another, the standard HE shell by itself comes in at 95 pounds. Thus sayeth Wiki.

http://en.wikipedia.org/wiki/155_mm_Long_Tom

Ammunition

The gun utilized separate loading, bagged charge ammunition. The propelling charge consisted of base (9.23 kg) and increment (4.69 kg). The data in the table below is for supercharge (base and increment).

Projectiles.[13][15][16]

Type Model Weight Filler Muzzle velocity Range

APBC/HE AP M112 Shell 45.36 kilograms (100 lb) Explosive D 2746 ft/s - 837 m/s 24075 yds 22,014 m

HE HE M101 Shell 42.96 kilograms (95 lb) TNT 2800 ft/s - 853 m/s 25714 yds 23,513 m

Smoke WP M104 Shell 44.53 kilograms (98 lb) White phosphorus (WP) 2800 ft/s - 853 m/s 25940 yds 23,720 m

Smoke FS M104 Shell Sulfur trioxide in Chlorosulfonic acid 2800 ft/s - 853 m/s 25940 yds 23,720 m

Chemical H M104 Shell Mustard gas, 5.3 kilograms (12 lb) 2800 ft/s - 853 m/s 25940 yds 23,720 m

Dummy Dummy Mk I Projectile – – –

Dummy Dummy M7 Projectile 43.09 kilograms (95 lb) – – –

Since it would be entirely justifiable for you to object that the M12 mounted the 155mm GPF, rather than the 155mm Long Tom, I checked on that, too. The HE shell for the 155mm GPF weighs exactly the same as that fired by the 155mm Long Tom.

http://en.wikipedia.org/wiki/Canon_de_155mm_GPF

Regards,

John Kettler

[Michael Emrys]

Ah well, as I said in another thread, "I may not always be right, but I am never wrong."

Michael

[John Kettler]

LiveNoMore,

Be grateful it was Titanium instead of Unobtainium. Otherwise, ALL your tanks would be Winchester and the bunker would still be shooting! And, yes, the term is used in military aerospace. I heard it myself on several occasions. We thought of it as being near zero weight, infinitely strong, easily formed and machined.

http://en.wikipedia.org/wiki/Unobtainium

Regards,

John Kettler

[womble]

LiveNoMore,

Be grateful it was Titanium instead of Unobtainium. Otherwise, ALL your tanks would be Winchester and the bunker would still be shooting! And, yes, the term is used in military aerospace. I heard it myself on several occasions. We thought of it as being near zero weight, infinitely strong, easily formed and machined.

http://en.wikipedia.org/wiki/Unobtainium

Regards,

John Kettler

Ah, Unobtanium, a transperiodic element in the same family as Handwavium and Imaginiarium.

Edit: I wonder if the atomic number of Imaginarium is the square root of -1? I'm pretty sure the atomic numbers of Un and Ha are surds. Or something like that.