When you sally against a siege,

If, at the beginning of the deployment stage, you find your army at say, the 9 o'clock position, and the enemy outside the gate at the 12; you may find your archers and slingers quite useful clustered on the wall at the corner of the wall at about 10:30. More often than not, the enemy will march around that corner to meet your infantry (which if sent marching out the 9 o'clock gate will usually "draw" them on around.) Skirmishers sent running after the enemy from the 12 will also increase their casualties. This can be quite helpful when your own army is small, and you find yourself besieged by a full stack almost every turn. You may not break every siege this way, but two or three sallies will cut them down to a really weak assault force when they do attack.

You do not have to engage with your infantry. Their mere presence near short of that corner will cause enemy casualties as archers and slingers, and even towers cut down their ranks. Save actual infantry contact for when siege towers are unloading and they are coming up the ladders. When you have a small army of 8 - 10 against a full stack, no lives can be thrown away.

If the way is clear, cavalry can finish off what the missile has whittled down, but don't send them to fight what the enemy has sent to block the cavalry. If you cannot run around them to cut down fleeing enemies, save your cavalry.

If you can draw their archers and slingers away from their spearmen, turn cavalry loose on them, but keep a hand on them to pull them out if they get too close to spears.

"Grouped" infantry will usually do well even if left alone. "Grouped" cavalry, even with your hands on them, will do what they feel like doing, usually with disastrous results. Example, I sent grouped cavalry to cut down archers. While one unit of four went after the archers, the other three units went right after spears, which had been a safe distance away. Fortunately, I saw what they were doing and realized they were "grouped" and "ungrouped" them fast. Then they did as they were told.

Strength and Honor

Celt Centurion