Garisson your cities and castles?

[SnowlyWhite]

militia for cities(how many are free upkeep, spear militia as they have 75 men - not that riots are the problem that it was in rtw, but... out of rtw habbit:p), 2-3 pessies in castles.

In all honesty... the ai attacks are obvious from so many miles away, you have plenty of time to get back(ok, I'm watchtower obsessed, and 90% of the time I have a spy in every enemy city on my border). Also, the ai NEVER(or ok, in ~10 long campaigns, I never noticed it) sieges you when you're already attacking one of his cities unless you share a huge border.
Combine the above with the ai's passion for carrying tons of siege eq/artilery which makes his armies crawl and you should have plenty of warning. Also, as a side note, never saw him assaulting in the 1st turn(even when he has siege eq., he'll just sit there patiently to build his ram only to bombard your walls in the next turn...).

When I just conquered the city:

- it already has a trained spy in it(I keep training them till they reach max. - just go in the city again and again every turn) so the chance he gets in a spy vs. my guy with 9-10 skill is close to nil(not that he uses the opened gates anyway, but...);
- I redo my units, and what needs training I gradually send back to retrain(3/turn, or whatever, so the garnisson is all the time still close to full);
- in the mean time I build churches/townhalls(everything useful that the ai never builds);
- stack is back to full, some militias are trained, go for the next city; or stay there, whatever...

When I don't want to attack the faction and it's obvious that he prepares to attack me:

- 6-7 spear militia; ok, prolly I'd use more if it'd be very late in the game, however, very late ingame you have so many troops that it hardly matters(and he has so few:p) plus probably you can field 2/3rds of a stack in any desired city in 1 turn when you feel he's about to attack(each city/castle produces 3 units, and you should have at least 2 cities near enough).
- 1-2 pessie archers(highly optional);
- 1-2 cav. units(to chase the routers). Mailed knights or whatever should do just fine.

This should hold perfectly against anything bar mongol/timurids, but those are another story anyway. When he sieges, I just drop all the imagination I might have and just blob my militias to repel his attack. He does 2 holes on the left wall section near the gate, 2 on the right, so I can put my schildoms there in the deploy fase as he always does them in exactly the same place. Make sure the units are close enough to the wall where I know he'll make the holes in order to allow only few soldiers in at a time. Abit on the left/right too, so he can't charge at all, because he'll have to go around the wall abit.
If he has a general, lucky me, because you'll kill him very fast(general being mounted and the ai charging like the french at crecy, needless to say the general reaches the hole 1st and insists in fighting your spearmen till he dies - I know that a bg unit can mop a spear militia like no tommorow on open field with charge, however he can't charge here).
If he doesn't have siege machines... you fight on the walls, which already gives a huge bonus... I put 4 or so militias on the walls, and the other 2-3 are sent where it seems to be hotter. If I want to be nasty, I pull my cav. out through the gate and charge in his back(main gate is just fine, he'll ignore you anyway - that suppossing he didn't use the ram, if he did... side gate). Charge in the back, his units already worn out abit, morale penality due to them being in a big blob... they break on charge like no tommorow...

[kublikhan3]

Unless I am defending against a crusade or Jihad, I keep just enough troops to maintain order. Everything else gets dumped into my field armies. This lets you take the fight to them, instead of sitting around with an expensive garrison waiting to get attacked.

[JCoyote]

If you have access to them, sword militia are great for defending walls, and inexpensive.

[mountain goat]

playing as denmark , norse swordsmen mixed with merc spear and any heav cav works fine.

norse swordsmen hold the line and cut through most units. spears hold up the gates or blocks in the walls , while cav charges the flanks .

[TevashSzat]

I say, if you can defend your city by just creating a killing zone at where ever the enemy breaks a hole in your wall, just mass at the city square. No matter what your enemy has, having a decent sized garrison right next to the city square fighting at bottlenecks will be extremely effective. Having 3 or 4 units of cavalry helps out too since the city streets are ideal for a charge because once a mass rout starts, your cavalry can just run down the streat and capture everyone

[gingergenius]

1. Try to have a general in each city. unfortunately for me, I have thousands of yoots in my family tree but none are of age and my other generals are dropping like flies. Not enough adoptions.

2. All you need is archers (preferably fire) and spearmen. Put all your archers on the walls facing the enemy, form your spearmen blocking off the gate and the main road through to the main square - enemy AI isn't able to work out another route to the centre square so make sure the main throughway is blocked off.

3. When the enemy begins to advance with its men, it might be worth moving your archers back behind the spearmen. Or you could keep them on the walls, where they will kill more enemy but suffer more losses.

[caius britannicus]

I find swordsmen miltia highly effective at defending cities. My garrisons are normally 50% sword militia (they man the walls, even on VH they can defend the walls against knights) 25% crossbow miltia (they are on the walls also firing on ladders and towers) and 25% spears who guard against cavalry that will eventually try to get into the city via the main gate. If the enemy has seige equipement I get all my men off the walls and defend the main square. The formation is normally spears defend the front of the choke point against cavalry charges while the swords wait behind. My crossbows are dispersed around the city (keep them moving) to fire into the flanks of enemies.

Cavalry is only so usefull. Inside the city they are just dead men riding horses slowly through the streets. Sometimes I send them out to try and get the siege equipment or attack the seige towers. I generally leave ladders alone because they are dead when they try and attack the sword militia on the walls and are whittled down by crossbows.