Quote Originally Posted by Stig
On this subject, what I don't get is that I can't destroy a tower with one unit of archers and the AI can. Do I place my units wrong or something? Or am I just an idiot?
You might be seeing the combined effect of archer fire and ballista/cannon towers.

If your defending archers are crowded around the gate they might be too far from the nearby towers to trigger their firing (in M2TW you need units near towers to make them fire). You want to see flags showing on all your towers in range of incoming siege towers and rams, which means they're "turned on." If you don't have enough archers spread out on the walls to trigger that, then place some of your ground troops at the base of the towers to trigger them. And try to upgrade to ballista or cannon towers when you have that option.