Battle Odds

[vmsbass]

I guess I am missing something, because the numbers don't seem to stack up. Allow me to explain:

I am defending with a Keshik with +10% Str and +25% vs Melee promotions against a Spearman with +10% Str and +20% Hill Def. So, the numbers as I see it are:

Spearman: 4 * 1.10 (Str) * 2 (vs mounted) = 8.8
Keshik: 6 * 1.10 (Str) * 1.25 (vs melee) = 8.25

Yet my friend said when he moused over to see the numbers he was getting something like 4.4 to my 3.6 (63% chance of victory, or roughly 2 to 1 odds); and it certainly played out like that, with his Spearmen winning most of the battles. But if my numbers are correct, shouldn't these battles have much closer odds? How do these numbers work?

 

[dirtyparrot]

Personally, I don't believe that the odds displayed are entirely accurate (I believe that PieceofMind has looked into this and is developing a more extensive odd displayer).

IIRC, combat bonuses are the only bonuses added to the attacker, the other bonuses (shock, etc) are substracted from the defender.

 

[JujuLautre]

There is a full article about that in the strategy articles section.

But basically:
- strength of the attacker is given from the original strength (including actual hit points) and its combat promotions.
- all other promotions and modifiers (terrain, river, defence...) are added together if they benefit the defender, and substracted if they benefit the attacker; if the net total R is positive, the result is applied to the defender positively (multiply by 1+R). If negative, it's applied negatively (divide by 1-R).

basically, except combat promos, things cancel each-other: city garrison cancels city raider, shock cancels shock...
So: speaman 4 * 1.10 (str) = 4.4
keshik: 0.1 (str) + 0.25 (melee) - 1.00 (spear vs mounted) = 0.65, applied negatively: 6/(1.65)

 

[PieceOfMind]

The main thing one has to keep in mind is that bonuses are always additive - not multiplicative. This is as with most modifiers used throughout the game, except it is not always clear (e.g. double production speed of walls for Protective leaders actually means +100% on base, which is not always the same as double the current rate).

The article Juju is talking about is Arathorn's Combat Explained.

@dirtyparrot,
The odds in Warlords and BtS are usually accurate. The only exceptions are on lower levels when one has free barb wins left, or occasionally when using siege units to attack and the damage required to kill the defender is a multiple of the damage per hit to the defender.

In earlier patches of Civ4 vanilla, there were deeper problems with the odds, because first strikes were not taken into account correctly (but they are now).

 

[vmsbass]

Thanks for the replies and link to that thread. Question answered