Does that mean giving your siege weapons a Combat promotion will allow them to do exactly the same amount of collateral as giving them a Barrage promotion?
No. Combat promotions don't change the base strength of the unit, nor do they change the collateral multipliers. Therefore, Combat promotions do not improve your collateral damage. It's a completely different calculation.
Phrederick said:
That's very interesting. In light of that, do you think there are any situations where barrage will be more useful than Combat/CR/Drill? What would you do if you had a single siege unit with a stack attacking a city? What about if the odds are 0.1% with Barrage and 0.2% with CR? The difference is so low that it seems like it would make sense to go with Barrage, if you knew that the roundoff wouldn't mean it made zero difference (Like a treb with Barrage I)
Here's a graph I posted when last looking into this (catapults vs longbows):
On the right hand edge of the graph, where things are really flat - yeah, I think Barrage is better. One way of thinking about this is that the Barrage promotion makes your catapult about 11% better (under the specific assumptions of that experiment - cats vs strength 6 defenders). So if City Raider isn't giving you that kind of improvement, you should go with Barrage. That doesn't necessarily mean 9% improved survival chances, though - you'd want to be looking at damage done as well, and possibly some other factors.
Where Barrage gets potentially complicated to evaluate is the impact that it has on subsequent attacks. Again - integer math. If the Barrage promotion allows you to catch a jump point, then you are getting a much better return on the investment than if you missed it.
You also want to consider how many units are vulnerable to a collateral attack. Barrage is more effective against a city with seven defenders than it is against a city with two.
But what's the opportunity cost of the Barrage promotion? There are two ways I see to look at this. One is to consider that you a city that contributes only catapults to the war effort (they are, after all, a decent size for whipping). Should you invest one catapult of hammers to first get a barracks? How many catapults do you need to attack with to see a profit on that investment?
Likewise, in a city that has a barracks, are you better off training three catapults, or two swords/crossbows/pikes/elephants? My hunch is that you'd rather distribute the promotions to the latter group, but I'd be happy to find out that I'm wrong if somebody else wants to do the experiment....
