Question about Fortresses

[Deathwalker]

Can some one help me. What use are fortresses. I’ve tried building them and ZOE never seems to work and they don’t expand your border. Can anyone give me a example of were there worth building?

[Marauder]

as far as i know, they only give a defensive bonus.

[SpencerH]

I almost never build them since I dont see much value. I guess a garrisoned fortess built on top of a resource that is near the border wouldnt be a bad idea.

[zulu9812]

They are supposed to give a zone of control, but it works differently to Civ2. Instead of preventing the enemy from moving past the fortress, units occupying a fortress (or indeed any unit with a ZOC) can take a kind of 'pot shot' at enemy units moving through that 9-square zone. However, it doesn't occur with every unit passing through the ZOC and I'm not sure what the formula is.

[SpencerH]

I've never seen evidence of the ZOC effect of fortresses but it could be like the naval defenses (I forget the correct term) that are very subtle.

[Willem]

I got into the habit of building them every other square in key areas, then putting a bombard unit in each, along with a defensive unit. The AI will almost always try to go through the middle, rather than fight the Fort. So by the time the enemy unit reached my city, they were usually pretty badly damaged, especially if the ZoC also kicked in. Which it very seldom does.

[Nym]

AFAIK fortresses only give a defensive bonus.
I usually use them to protect strategic places like mountain near a border city.