Real quick, Lemon, what does Siege do?
Cities have a passive defense bonus of 25%+25% per defensive building. Siege reduces this by the strength of the siege bonus. It does not affect terrain defensive bonuses.
Damn ninjas.
I think they stack, but I'm not 100% sure. You can check in the admin interface if you want.
So, uhhh...
What does defensive bonus do, exactly? And what bonuses do the different terrain bonuses give? Wouldn't, to a certain point, bowmen be able to rain death without retaliation if there was a wall and the attackers don't have a siege weapon? And don't the Stone Wall and Fortress give +50% each? That's what the 50 means right?
And even though I know you almost certainly won't answer this: When is the best time to use siege weapons, then? After all, they're rather slow.
Defensive bonuses simply increase the defense stat of all defending units. If they get a +125% defensive bonus (+50% from hills and +75% from a city), then a unit with 4 base defense goes into battle with 9 defense.
As for terrain, forest/hill/mountains get +25/50/75% defense.
Walls don't have any physical presence in a battle, and give the same percentage bonus for all defending units, from bowmen to axemen to calvary to boats. That said, in a battle with forces that are even slightly similar, a defender with a good bonus will be able to shred his opponent with the crazy defense he can get.
Yeah, 50 is a 50% bonus, I made a mistake when I said that they were all 25% apparently.
You should use them when it is benifical, i'm not really going to tell you when that is, but you should be able to figure out when it is more useful to send some over and wait the turns it takes to get there then to produce a few more regular troops and attack a few turns sooner.