Defense Multipliers

[Edward]

A while back someone posted detailed information on how defense multipliers worked. I was surprised to find out that certain multipliers don't work together. However I can't remember which ones!

Possible defensive strength multipliers are:

Terrain
City Walls, SAM, Coastal Fortress
Fort (built by settler/engineer)
Veteran
Unit is Fortified
Misc (Pikeman vs. horse, Aegis vs. Missle)

Obviously you're not going to get the benefit of both a fort and city walls, but I remember a startling combination that didn't work. Something like "being fortified is meaningless behind a city wall".

Thanks

[Xin Yu]

I haven't really tested it but I tend to believe in it:

attack=8*base-attack*vet
defense=8*base-defense*vet*terrain*flag*max-modifier, where

base-defense=defense factor of the unit;
vet=1.5 for vet, 1 for non-vet;
terrain=terrain modification;
flag=1.5 if the defender has 'x2 vs mounted' flag and the attacker is a land unit with move=2, hp=1, and fp=1;
flag=3 if the defender has 'x2 vs air' flag and the attacker is a non-missile airunit;
flage=5 if the defender has 'x2 vs air' flag and the attacker is a missile unit;
max-modifier=maximum of all other modifiers, fortified=1.5, fortress=2, wall=3, etc.

Fortified units behind city walls will be useful if being attacked by units ignoring city walls (howitzer, bomber, etc.)

Special rules: fighter gain advantage against helicopter, partisan gain advantage against 0-attack units (settler, diplo, caravan, etc.), ships in city are not protected by walls and are punished when attacked by land and air units.

After attack and defense factors are calculated the odds are calculated as follows:

if attack<defense then probability of attack win=(attack-1)/(2*defense);
if attack >=defense then the probability of attack win=1-(defense+1)/(2*attack).
In other words the weaker of the two (attack, defense) gets punished twice the difference of attack and defense.
Remember that both attack and defense have been multiplied by 8 and there is no round-down.



[This message has been edited by Xin Yu (edited June 09, 2000).]

[Aurelius]

[quote]<font size=1>Originally posted by Xin
Fortified units behind city walls will be useful if being attacked by units ignoring city walls (howitzer, bomber, etc.)

Wow, I've always assumed that the units got both the fortified bonus and the city walls. Well, one thing is 'certain', it's good to be fortified behind city walls as your units repair faster.

"partisan gain advantage against 0-attack units (settler, diplo, caravan,
etc.)"

I've always suspected such concerning Partisans vs engineers. Thanks Xin, can AI partisans pick out what they attack in a stack? It's uncanny how they always kill my engineers when stacked with superior defensive units.

Anyone, I don't seem to be able to get the answer to the question, "is there an advantage to attacking from defensive enhanced terrain?" (I've always wondered if a unit gets the defense when attacking)

later

Edited to increase font size...
[This message has been edited by Aurelius (edited June 09, 2000).]

[Hasdrubal]

quote: Wow, I've always assumed that the units got both the fortified bonus and the city walls.

So did I. They don't?

quote: "is there an advantage to attacking from defensive enhanced terrain?" (I've always wondered if a unit gets the defense when attacking)

No, if you attack then you don't recieve a terrain-related bonus.

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Ceterum censeo Romanem esse delendam.
[This message has been edited by Hasdrubal (edited June 08, 2000).]

[Edward]

Thanks, Xin Yu, for the excellent and thorough answer.

[cavebear]

In a recent game against the AI, I became very frustrated when my Alpine units were being wiped out by Armor. The Alpines were fortified behind city walls on grassland. I thought they would have a defense of 21 (5*1.5 = 7.5, rounded down to 7, and 7*3=21). The Armor attacks with 10. Even if the AI had Sun's or the Armor was veteran, the attack should only be 15. The Armor won over 1/2 the time. It did not matter whether the Alpines were fortified or not (20 tests of each).

Conclusion 1: Fortifying within city walls generally has no value (there are specific exceptions, as Xin noted). I do it anyway on general principles.

Conclusion 2: The AI cheats. We know it builds with fewer shields, but I think the battle calculations are fudged as well.

[Sten Sture]

I have seen several references lately to city walls tripling defensive strength, whereas I have always thought it was just doubled.

Help?

[Aurelius]

Didn't catch the stop fast enough.
[This message has been edited by Aurelius (edited June 09, 2000).]

[Aurelius]

quote: Originally posted by Sten Sture on 06-09-2000 05:16 PM I have seen several references lately to city walls tripling defensive strength, whereas I have always thought it was just doubled. Help?

I was surprised to find that city walls triple defense too. But both my MPG and V2.42 specifically mention it in the Civilipedia.

[Smash]

civlopedia says defense tripled against all ground units cept howies

[Sten Sture]

but is it right??

cavebears example makes it look doubled.

vet armor 15 vs vet alpine behind walls if 2x = 14... vet armor wins >50%

[Xin Yu]

In my previous post I did not mention HP and FP. By saying 'win' I meant winning one round, which causes the enemy to lose FP points out of 10*HP.

Armor has a better FP than Alpine. And the alpine maybe not vet?

[SCG]

quote: I have seen several references lately to city walls tripling defensive strength, whereas I have always thought it was just doubled.

Some of the confusion might be from the fact that city walls ignore fortification. So a fortified unit would be effectively doubled from what it would be out of the city (1.5 x 2 = 3) It actually defends as an unfortified unit would (1 x 3 = 3).

You might be able to think of it this way. If you barricade the doors behind city walls, you are less mobile to do things like dropping burning oil down on the attackers from above - you are harder to get to, but it is also harder for you to get to the attackers.

Another way to look at it is city walls are just a souped up fortifying process that stays.

And Sten, it is discussed in another thread recently that the armor wins more often because of other factors like hit points, not because of the attack strength and defense strength.

[Sten Sture]

d'oh! I knew that - sorry.

the hit points and fire power thing...
[This message has been edited by Sten Sture (edited June 09, 2000).]

[DaveV]

Here's how I get a quick estimate of battle odds. It's an oversimplification, but pretty accurate. In Xins's formula above, I use Attack*HP*FP for the base attack, and Defense*HP*FP for the base defense. So in Cavebear's example, the Alpines are 5*2*1 (base) * 3 (city walls) = 30. The attacking Armor is 10*3*1 (base) = 30. So I'd expect even results, as Cavebear is reportign.

By the way, this calculation explodes the old myth about vet pikemen being better than musketeers. Vet pikes are 2*1.5*1.5 = 4.5; muskies are 3*2 = 6. If the muskies become vets, they are 3*2*1.5 = 9, twice(!) as good as a vet pike. And the muskies are 3*2 = 6 on attack, the equivalent of a catapult.