There's an aspect of sieges that one rarely sees in fantasy: urban warfare. Or, at least, I haven't seen much. (recommendations?) Even personal-level fantasy warfare on a battlefield can be difficult to find -- warfare, that is, as in organized group fighting. I heartily recommend Bernard Cornwell's Warlord Chronicles for its close-up view of first-millennium-AD warfare if you're looking too. He puts you right in the shield wall with his MC.
One can find resources about urban warfare online with a little work. It's all modern urban warfare, of course, where hand-to-hand combat is far less common. Those principles will still apply whenever archers are available, but that still leaves the question of your average medieval-based fantasy soldier who's carrying around a sword or a spear and a shield.
Briefly, the range-weapon urban warfare skills to keep in mind are:
- Stay under cover as much as possible. Out of sight, essentially -- don't be a target to shoot at.
- Move fast when you must cross open spaces. This includes knowing where you're going and where any obstacles may be.
- Be alert! Watch for lines of fire, especially from above, double check everything, and be paranoid.
Questions of squad size will come into play, but these techniques can be adapted to small groups of men in potentially tight spaces.
Weak center: This might not work in a narrow side street, I think, but perhaps on a wide street or in a square. The center of the shield line, here, is deliberately "weak" and falls back when the enemy presses in. Being eager, the enemy keeps pressing and the overlap of their shields loosens up. The men to either side of the weak center can attack into the gaps, or even swing around completely and stab the enemy in the back.
In combination with the range-weapon tactics mentioned above, this should make for an interesting part of the story. Though by "interesting" I mean "brutal, messy and scary" of course. And what would happen if I throw half a dozen knights on horseback into the mix?
Have you ever researched small-group fighting tactics? I haven't had a chance to mention the military references I found on I, Clausewitz's blog -- this is my chance, I guess. Recommendations and references welcome, as always!