[OmikronWarrior]

I do not think anyone has ever written formally on forts.

But there are some rules of thumbs.

1) From the start, forts are mostly needed to start recruiting additional national commanders, especially mages to speed along research. This means placement and type are less important than build time and cost. Hence, swamp provinces (usually only 800 gold and 3 turns to build) are great places to place forts.

2) As the game progresses, more forts will be built and upkeep costs will rise resulting in less gold to spend on new commanders and troops every turn. Thus, building new forts does not result in the ability to recruit additional commanders per turn as gold is now the limiting resource.

3) Forts are excellent, albeit very expense defensive structures. Building them on particularly rich provinces or provinces with important sites can be a good investment.

4) Every nation has different types of forts with different stats. In general, high fortification is less useful than high administration and supplies, espeically if costs are equal.