Quote Originally Posted by Tiberius Nero
Even if you end up defending against an attack to the fort (which is unlikely, since tha AI always wastes a turn when besieging, builds equipment on the second and attacks on the third, if it has enough equipment, and a fort can only withstand 3 turns of siege), even then you are at a disadvantage as opposed to an open field battle, as siege battles are brutal for both sides, little maneuvering is allowed in the bugged alleys of forts and it practically boils down to man-to-man combat, with little flanking. Cavalry is also useless in fort battles.
Forts are good to winter in, though, it seems. I've found that my generals are less likely to get sick in a fort during the winter.

It would be awesome if you could build permanent forts of stone, though. Which the Romans did do on their borders. Stone forts with long siege-times would make building forts more advantageous.

The great thing is they'd become strategic locations that could be captured by an enemy, adding an interesting little layer of strategy.