[Norfleet]

Originally posted by Sheap:
Castle walls don't "regenerate" unless the siege is lifted (in which case they are repaired fully), or a spell such as Arcane Masonry is used.

Castle walls will be fully repaired if the siege is broken and the province reverts back to the owner's hands. Castle walls *DO* regenerate if the defender's strength now exceeds the attacker's strength, such as if the attacker withdrew forces, the defender summoned or teleported in more units, the attacker was attacked and suffered casualties, or the attacker attempted to storm with some of his forces and failed.