Attackers choosing Combat promotions
Combat promotions are unique because they are the only modifier promotions that always affect the unit who owns them. (Drill promotions also always affect the unit owning them but I don't call them "modifier" promotions). All other modifier promotions such as City Raider and Shock always affect the total defense modifier of the defender.
When defenders have a large number of defensive modifiers (defense bonuses if you prefer), a promotion which subtracts a fixed amount (e.g. 20% for CR1) becomes relatively less useful compared with a 10% increase on the attacker's strength that a combat promotion would provide.
Now I know a lot of you hate the maths so I'll completely avoid it this time other than giving you the end formula. However, you will need to know what the variables in the formula are:
Let C be the number of combat promotions you are considering taking.
Let A be the number of combat promotions you already have.
e.g. if you are deciding between C2 and shock but already have C1, then you are considering the case that C=1 and A=1.
Let TDM be the Total Defense Modifier. Those of you using the latest version of Advanced Combat Odds will have this value readily available (as long as you have it enabled from options) but for everyone else you need to work it out very carefully. To calculate the Total Defense Modifier, you add up all of the bonuses that the defender has including penalties on the attacker (like 50% amphibious penalty), and then you subtract all the bonuses the attacker has excluding combat promotions.
Assuming the total defense modifier is not negative and we exclude the possibility of Combat VI (it has +25% bonus instead of +10%), the following formula will apply. (When the total defense modifier is negative, something which is fairly rare anyway, the choice between combat and another promotion becomes less interesting and is not really relevant to this discussion.)
Let X be the equivalent reduction in the defender's total modifier.
Then,
This might be confusing without the help of an example.
Example
Here I have an Infantry trying to amphibiously attack an injured Rifleman.
Even though the rifle is already fairly injured, the infantry is still going to have trouble surviving the attack because there are so many defensive bonuses including some City Garrison promotions and 25% for being on a hill.
The attacking infantry has the option of choosing Combat 2 or Pinch. (It could also take Drill 1 but that is for another discussion.)
The screenshot was taken using ACO so the Total Defense Modifier is already shown at the bottom for us. Note that in ACO the "+25% Vs. Gunpowder Units" bonus is actually shown instead as a negative modifier on the defender (but still in green). This makes it a bit easier to see how the total defense modifier is reached.
The attacker already has +10% strength from his Combat 1 promotion but this is shown under the modifiers for the attacker instead. If you are not using ACO, that 10% strength modifier would be in the list with the defense modifiers so you need to be careful to exclude it from the TDM calculation.
So we have:
C = 1. (we are considering taking 1 combat promotion)
A = 1. (we already have one combat promotion)
TDM = 130.
So X = (100 + 130) * 1 / (10 + 1 + 1) = 19.17%
This tells us that if we were to select the Combat 2 promotion for the infantry, it would have the same effect as a promotion which gave -19.17% on the defender. In other words, Combat 2 in this situation is about as good as City Raider 1. Considering this infantry might be trying to reach the Amphibious promotion at 5xp (with Combat 1 and 2), Combat 2 might even be preferable to Pinch. It's up to you to make decisions like that.
For Dummies
If you really want to avoid doing any maths you could instead use a table of some values. Let's try that now...
If we already know A (how many combat promos we have) and C (how many combat promos we are considering taking), we can find the values of the total defense modifier that would make the equivalent reduction in defense modifier exactly the same as some standard value like 20% or 25%. I say 20% or 25% because promotions like City Raider 1, Shock etc. typically have 20% or 25% as their modifiers.
For Really Dumb Dummies
(Heavily simplified)
Combat 1 beats City Raider 1 when the total defense modifier is more than 120%.
Combat 2 beats City Raider 2 when the total defense modifier is more than 170%.
Against a gunpowder unit, Combat 2 beats Combat 1 + Pinch when the total defense modifier is more than 200%.
Combat 1+2 beats Combat 1 + City Raider 1 when the total defense modifier is more than 140%. (e.g. Aggressive civs or quechuas)
If you have a request for another simple rule, please mention it!
Combat promotions are unique because they are the only modifier promotions that always affect the unit who owns them. (Drill promotions also always affect the unit owning them but I don't call them "modifier" promotions). All other modifier promotions such as City Raider and Shock always affect the total defense modifier of the defender.
When defenders have a large number of defensive modifiers (defense bonuses if you prefer), a promotion which subtracts a fixed amount (e.g. 20% for CR1) becomes relatively less useful compared with a 10% increase on the attacker's strength that a combat promotion would provide.
Now I know a lot of you hate the maths so I'll completely avoid it this time other than giving you the end formula. However, you will need to know what the variables in the formula are:
Let C be the number of combat promotions you are considering taking.
Let A be the number of combat promotions you already have.
e.g. if you are deciding between C2 and shock but already have C1, then you are considering the case that C=1 and A=1.
Let TDM be the Total Defense Modifier. Those of you using the latest version of Advanced Combat Odds will have this value readily available (as long as you have it enabled from options) but for everyone else you need to work it out very carefully. To calculate the Total Defense Modifier, you add up all of the bonuses that the defender has including penalties on the attacker (like 50% amphibious penalty), and then you subtract all the bonuses the attacker has excluding combat promotions.
Assuming the total defense modifier is not negative and we exclude the possibility of Combat VI (it has +25% bonus instead of +10%), the following formula will apply. (When the total defense modifier is negative, something which is fairly rare anyway, the choice between combat and another promotion becomes less interesting and is not really relevant to this discussion.)
Let X be the equivalent reduction in the defender's total modifier.
Then,
This might be confusing without the help of an example.
Example
Here I have an Infantry trying to amphibiously attack an injured Rifleman.
Spoiler :
Even though the rifle is already fairly injured, the infantry is still going to have trouble surviving the attack because there are so many defensive bonuses including some City Garrison promotions and 25% for being on a hill.
The attacking infantry has the option of choosing Combat 2 or Pinch. (It could also take Drill 1 but that is for another discussion.)
The screenshot was taken using ACO so the Total Defense Modifier is already shown at the bottom for us. Note that in ACO the "+25% Vs. Gunpowder Units" bonus is actually shown instead as a negative modifier on the defender (but still in green). This makes it a bit easier to see how the total defense modifier is reached.
The attacker already has +10% strength from his Combat 1 promotion but this is shown under the modifiers for the attacker instead. If you are not using ACO, that 10% strength modifier would be in the list with the defense modifiers so you need to be careful to exclude it from the TDM calculation.
So we have:
C = 1. (we are considering taking 1 combat promotion)
A = 1. (we already have one combat promotion)
TDM = 130.
So X = (100 + 130) * 1 / (10 + 1 + 1) = 19.17%
This tells us that if we were to select the Combat 2 promotion for the infantry, it would have the same effect as a promotion which gave -19.17% on the defender. In other words, Combat 2 in this situation is about as good as City Raider 1. Considering this infantry might be trying to reach the Amphibious promotion at 5xp (with Combat 1 and 2), Combat 2 might even be preferable to Pinch. It's up to you to make decisions like that.
For Dummies
If you really want to avoid doing any maths you could instead use a table of some values. Let's try that now...
If we already know A (how many combat promos we have) and C (how many combat promos we are considering taking), we can find the values of the total defense modifier that would make the equivalent reduction in defense modifier exactly the same as some standard value like 20% or 25%. I say 20% or 25% because promotions like City Raider 1, Shock etc. typically have 20% or 25% as their modifiers.
For Really Dumb Dummies
(Heavily simplified)
Combat 1 beats City Raider 1 when the total defense modifier is more than 120%.
Combat 2 beats City Raider 2 when the total defense modifier is more than 170%.
Against a gunpowder unit, Combat 2 beats Combat 1 + Pinch when the total defense modifier is more than 200%.
Combat 1+2 beats Combat 1 + City Raider 1 when the total defense modifier is more than 140%. (e.g. Aggressive civs or quechuas)
If you have a request for another simple rule, please mention it!
