City Defense Bonus

I am curious about the city defense bonus -- i know there are two seperate values, one for cultural strength and one for physical fortresses. I know they are exclusive. So...

1) What is the formula for determining a city's cultural defense status? How can I predict when one of my city's will grow in defense ability -- it seems to be in multiples of 20%? What is the rate of recharge for battered defenses?

2) If your "higher value" defense gets battered to a point where the other defense now has a higher value, will they swap? That is, let's say your cultural bonus is 80% but you had walls as well -- let's say some catapults took your cultural level down to 40% ...would the walls then kick in at 50%?

3) When to fortifications become obsolite? I read that gunpowder units and above ignore walls when attacking, which sort of makes sense, but it says in the manual that units above musketmen cannot also utilize walls?

So, Musketmen in a walled city get no bonus when defending against macemen? That does make much sense to me...

I guess I feel that musketmen would still have a hard time attacking a city with walls, especially if arrows and crossbows were raining down on them. But, I suppose this is also a tangible benefit to musketmen that isn't really advertised -- whereas they only have 1 greater strength than a maceman, they will be able to ignore all the fortification bonuses.

While the defense value comes from two separate sources, they simply stack and give a single city defense value.

Culture gives something like 20% for each expansion of the city's culture, and so it will increase at the same point the culture does. It recharges a few percent each turn, though I think the rate increases with each turn the city isn't bombarbed.

Castles are basically obsolete with gunpowder, because I think all the units after that ignore them.

While the defense value comes from two separate sources, they simply stack and give a single city defense value.

Click to expand...

I didn't think they did stack! The manual states that your defense bonus will be which ever value is higher - so if you have walls (50%), and your culture is 80%, the total bonus isn't 130%... but just 80%. That's my understanding...