Quote Originally Posted by Didz View Post
Tactically, 'Do NOT try to defend the walls.' ....the number of casualties you inflict will be minimal and the troops you place on the wall are irrelevant in defending the winners circle. The AI will either kill them quickly or by-pass them and make a run for the centre. Any troops placed on the walls should be considered nothing more than a 'speed bump' sacrifice, so militia or other weak troops are the most that should be wasted on the task.
It is possible to defend the lowest level fort walls efficiently. To some extent it is also possible with the 2nd level fort, but a complete waste of time with the star fort.

Remember, that once the walls are captured the gates become unlocked, so beware of enemy cavalry charging through the gates into the rear of your defences.
If you are defending (as opposed to defending when 'intercepting') you can deploy field defenses within the fort. Stakes at the gates (slightly off the gates, closer to the center) prevent cavalry from entering unless they blow a hole in the wall with their artillery. This is not common though (unfortunately). The AI just makes a dash for the walls (and the center); cavalry follow; once their infantry is destroyed (while cavalry lingers at the stakes), the artillery crews abandon their guns and make a dash for the 'center'.

Artillery: Indirect fire artillery should be placed around the centre of the fort and used to lob shells over the wall at the attackers. They may also be able to hit the enemy on the opposite wall if placed carefully (remember they have a minimum range).
I never had success with indirect artillery in fort defense. Direct artillery: that's a different story, especially in star forts (where they can be properly defended by infantry in "V" formation).

Cavalry: Not a lot of use to be honest....in fact it tends to get in the way. But if you have some I found it best to stick it in the corners of the fort as far from the action as possible and use it as a last resort to deal with any crisis situation.
A unit or two of light cavalry (preferrably: light dragoons who can join the fight in the fort on foot later on) hidden in the bushes by the fort can come in handy to destroy AI artillery.

Buildings: These are often useful for sticking poor quality units into, but personally I wouldn't recommend sticking decent infantry into them as the rate of fire from the windows is much reduced, and to be honest the last thing you want is to have melee heavy infantry chasing your men around inside a building.
Light infantry (all types) shine in buildings. Note though that post patch, AI's priority #2 (if not #1) is to assault buildings. So, entrances should be protected.

That's my 2 cents ;)