Posting this one because the numbers are a good illustration of what a wall actually does.
Attacker: roughly 6,000 axes, 900 light cavalry, one ram stack
Defender: 2,400 spears, 800 swords, wall 20
Result: attack repelled, wall down to 17, all attacking troops lost.
Morale was at 78% — they are bigger than me but not enormously — and luck came in at −8%, so this was not a fluke roll. The wall did the work. At wall 12 the same stack takes the village comfortably.
Rebuilding the wall cost about four hours of production. Cheapest defence I have ever bought.