Against a full stack of elite (although early period) Venetian troops led by a great general, I found that only 7 town militia did the trick in Vienna.

Firstly, town militia took out their ladder unit as it climbed, routing their Venetian militia spearmen. Then two units of town militia took on the seige tower's forces from both sides, and took heavy losses before the Venetian unit routed.

Next, I had three units line up in front of the gate in a 5 or 6 soldier-wide, deep unit formation, set to GUARD. Then, the unit which repelled the laddermen came down and stood on the left flank, in the same depth formation, set to attack, aligned towards the gate itself.

Next, I pulled my remaining town militia off the wall after routing the seige tower's forces, and set them to attack in a complimentary fashion from the right flank.

Finally, the ram broke through the gate and I had the two flanks charge the unit coming through, making contact simultaneously from both sides, forcing an almost instant rout.

Then the general broke through with his heavy militia spearmen and his mounted guard, and forced a pocket to form. The units in guard mode held formation while the flankers attacked from the sides, stopping the advance and also simultaneously wore down the enemy morale.

Slowly, one by one, the general lost his guard units, but even more than that, the surrounded enemy could not fight off my inferior, unupgraded, novice town milita. This was on very hard, very hard by the way, as the Danes in a recent posted campaign.

Finally I slew the general himself, after approximately 37 percent of his force was already dead. Routing did not follow immediately, as I had to slay even more of his elite troops. Even after 81 percent of his army lay dead, routing units continued to return against me.

Finally I ended up sallying against his remaining hundred archers and spearmen who stopped routing and started peppering me with arrows. It was a heroic victory.

(I'm familiar with the grammatical usage of 'an' heroic victory, but I feel it is an outdated and inconsistent rule, therefore I aim to eliminate its usage)

Spoiler Alert, click show to read: 










I say that town militia are all you need except against late period units... but by that time, I have too much territory to bother defending anything, merely seeking and exterminating any and all who attempt to resist my rule. And against the Hordes, I prefer an active, aggressive defense over seige defense anyway. Night fighter and high chevron generals paired with infinite mercenaries/veteran spearmen/heavy cavalry.

Guarding walls? Militia units and archers are all you ever need. The game rightly gives defenders an advantage on the walls. This is the militia men's home, they will fight to the death to protect it from an invader, especially while they still have the walls in their possession.

Version: LTC (not latest version, however) and latest vanilla.