Attacking bunkers

Started by Amra, 13 May 2021, 02:19:06 PM

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Steve J

I would have thought the Churchill AVRE with Petard mortar would count too, given it was designed for this sort of role.

Ithoriel

The Russian B-4 203mm tracked howitzer (same chassis but smaller gun than the Br-5 280mm mortar)  was known as "Stalin's Sledgehammer" for it's ability to reduce fortifications to rubble. I suspect lots of larger artillery pieces should have a "bunker buster" ability.

We assumed the "six to hit" represented the need to concentrate fire on specific points to collapse the structure, rather than plastering it haphazardly with fire.
There are 100 types of people in the world, those who understand binary and those who can work from incomplete data

sultanbev

The Germans used 88s against pillboxes and steel turretted bunkers on the maginot line (and probably others) so that is where their bunker buster rating comes from. Having said that, any high velocity gun large calibre could do the same with armour piercing, so all the following should also be rated as such:
3.7" AA
85mm AA
90mm AA (French & US)
10cm K18 gun
10.5cm Flak39
12.8cm PAK44/Jagdtiger
M12 SP 155mm, M2 Long Tom
ISU-152, ISU-122
122mm M31/37 corps gun
Russian 152mm field guns
Russian 107mm corps gun various makes
Japanese 105mm and 150mm field guns (not howitzers)
KV-2 (had concrete piercing ammo)
203mm B4 (had concrete piercing ammo)
Sturmtiger (does have a HEAT round)
No doubt there'll be others.

As for hitting a bunker, it did depend on how much cover it was in. The Japanese log bunkers were particularly difficult to see in Asian theatres. Allied tanks eventually developed a procedure where they used canister or HE to blast away the camo scrub and netting, AP round to penetrate the bunker wall, then HE through the hole just made, and if that failed they drove the tank onto the bunker roof and ground the logs down with the tracks, or brought up a flamethrower.

In Europe the bunkers tended to be more substantial but more obvious, so AP was the first shot, then HE through the hole. The AP was fired at the weapons slits where possible, so even if it didn't penetrate the concrete it might get through the firing slit and wreak havoc inside, or send splinters in that would damage weapons and crew. Sometimes they fired WP/smoke first to blind the gunners inside. So for BKC, I would have thought using the A/T factors should be the primary direct fire factor used.

The AVRE Petard was a bit different in that it used what was an early version of HESH in effect, so was a bunker buster on steroids. The 15cm sIG33 (Brummbar, etc) is different again as it had a HEAT round which might have an effect on bunkers, but was more for demolishing houses and MG nests. It's low velocity HE round cannot be compared to a 155mm Long Tom HE round for example.

In my own rules I just treat bunkers as hull down tanks with armour thicknesses converting concrete to steel at 1:4.5 ratio taken from the Morrow Project rules, eg an 18" thick pillbox is the same as 4" of steel armour, ie the same as a Tiger I, then special damage rolls modified by the weapon used, and whether the hit could penetrate or not. Bunker "armour" varies from 1-6cm for log and earth MG nests, around 10-12cm for pillboxes, up to 35cm for Atlantic Wall command bunkers.

pbeccas

A can of worms has been opened 😀

I guess this is why it's easier to target the unit inside.

Amra

OK all interesting ,although not directly concerning the Western Desert .

So do we have an actual BKC4 rule supporting the Bunker Buster special ability ?

How do you destroy a bunker ?

Big Insect

Six to Hit & Six to Save is the intention for BB weapons. Exactly as Ithoriel states.

The reason for Six to hit is not anything to do with its size - it is to do with the fact that you need to hit most big bunkers in the right place to do them (or their occupants) any significant damage.

In the game 'Bunkers' can range from a small (ish) Japanese log-bunker right up to a Maginot Line type monolithic building.
For the bigger western reinforced concrete type bunkers - particularly on the Atlantic Wall - you could play a house rule based on 'Hit on a 3' but 'Save on a 3'. We use that sometimes in FWC for assaults on large fortified complexes.

You also had the situation in the Winter War, where the Finns repeatedly poured water over their bunkers to create a dense layer of ice over the surface, in addition to the concrete and steel structure. The only disadvantage to this was that it made the bunkers look glossy black and so they stood our against the snow - although some defenders then ended up applying a painted on white camo as well. How you'd reflect the protection of an 'enhanced' bunker like that is a good question - but the soviets dealt with them by driving their big tracked 'mortars' up to within a couple of hundred yards and shooting at the bunkers over open sights!

As with all things BKC - it really does depend upon the level of extraction you want to go to. I am sure that all of the weapons listed by Sultanbev would have some sort of BB capability, but against different types of bunkers they would be more or less effective. The BB designations is easily added at the extra points cost showing for Special Abilities, as you see fit in your own game.
NB: this is not a set of WW2 siege rules - the section on fortifications and fighting in buildings is added very much as an 'add-on'.
'He could have lived a risk-free, moneyed life, but he preferred to whittle away his fortune on warfare.' Xenophon, The Anabasis

This communication has been written by a dyslexic person. If you have any trouble with the meaning of any of the sentences or words, please do not be afraid to ask for clarification. Remember that dyslexics are often high-level conceptualisers who provide "out of the box" thinking.

Raider4

Quote from: Amra on 17 May 2021, 07:24:31 AM
How do you destroy a bunker ?

617 Squadron and a dozen Tallboys?*


* The 1945 version of "Take off and nuke it from orbit, it's the only way to be sure".

Amra

Cheers Big Insect ,that helps
It's hit on 6 and saves on 6
But how many hits does a bunker take ?

Big Insect

6
Hits come off like other units at the end of the turns and Bunkers cannot be suppressed (but Occupants can).
Cheers
'He could have lived a risk-free, moneyed life, but he preferred to whittle away his fortune on warfare.' Xenophon, The Anabasis

This communication has been written by a dyslexic person. If you have any trouble with the meaning of any of the sentences or words, please do not be afraid to ask for clarification. Remember that dyslexics are often high-level conceptualisers who provide "out of the box" thinking.

Ithoriel

Quote from: Big Insect on 17 May 2021, 04:21:07 PM
6
Hits come off like other units at the end of the turns and Bunkers cannot be suppressed (but Occupants can).
Cheers

So you need an average of 36 dice to demolish a pillbox? Presumably the nano-repair-bots fix a pillbox that has taken 5 or less hits? :)

Our version with 2 hits for an earth and wood bunker, 3 for a concrete one, 4 for a medium structure and 6 only for the largest command posts or gun batteries and with hits not slowly recovering every turn, unlike troops, looks very feeble by comparison.
There are 100 types of people in the world, those who understand binary and those who can work from incomplete data

Amra

Thanks,is that in the rules anywhere I missed ?
The only bunker buster has 5 shots , so better activate lots of times !

Big Insect

Quote from: Ithoriel on 17 May 2021, 05:04:33 PM
So you need an average of 36 dice to demolish a pillbox? Presumably the nano-repair-bots fix a pillbox that has taken 5 or less hits? :)

Our version with 2 hits for an earth and wood bunker, 3 for a concrete one, 4 for a medium structure and 6 only for the largest command posts or gun batteries and with hits not slowly recovering every turn, unlike troops, looks very feeble by comparison.

That looks like a very sensible approach
The thing for me from a mechanism approach is consistency - if you keep hits on units, I'd suggest you keep them on fortifications, and vice-versa.
As stated previously - the 'challenge' is that of course a single Bunker model actually represents more than just 1 Bunker on the table.

Cheers
Mark
'He could have lived a risk-free, moneyed life, but he preferred to whittle away his fortune on warfare.' Xenophon, The Anabasis

This communication has been written by a dyslexic person. If you have any trouble with the meaning of any of the sentences or words, please do not be afraid to ask for clarification. Remember that dyslexics are often high-level conceptualisers who provide "out of the box" thinking.

Ithoriel

We allow regular units to recover 1 hit at the end of their player turn. Elite recover two. Greens and Fanatics none. It is not possible to recover the last hit point, so units once damaged become a little easier to kill. So ... consistency? .... what's that? :-D

It does mean that it is worth pulling regulars and elites back to recover, if you can.
There are 100 types of people in the world, those who understand binary and those who can work from incomplete data

Ithoriel

Quote from: Amra on 18 May 2021, 02:47:46 AM
Thanks,is that in the rules anywhere I missed ?
The only bunker buster has 5 shots , so better activate lots of times !

Our little group tends to take the rules as written as suggestions and a starting point, following Douglas Bader's dictum,"Rules are for the guidance of wise men and the obedience of fools." If we haven't added at least half a dozen house rules to a rule set we probably haven't played them. :)
There are 100 types of people in the world, those who understand binary and those who can work from incomplete data

Itinerant Hobbyist

Great discussion and this kind of flexibility is what I like about BKC