How many fortresses to build?

[TwoBits]

Patrol is the only command available to defend a province with a fortress, unfortunately.

Personally, it sounds like some people are building too many fortresses. The original poster had 7 for 18 provinces. Wow! That's a lot of gold expenditure that could have otherwise gone into, well, a lot of things - like researchers, commanders, or more conventional forces to take more land and go on the offensive.

Remember, a fortress only stops an enemy who wants to besiege you. They're not forced to stop there - they can bypass the place and keep on attacking elsewhere. The AI probably won't do that very often (ever?), but an SP player would certainly consider doing it...