"The loyalty and security of a settlement is affected by a number of things, such as if there is a culture mismatch between the settlement owner and its inhabitants, whether the town was recently captured, the strength of the garrison, kingdom policies, governor skills, and so on...," the developer outlines in the strategy game's sixth development update post. When a settlement's loyalty dips, the dev explains, you'll find more and more of its hitherto happy Folk will start to "take up arms in the form of militia".

If that militia hits a tipping point - that is, if it feels it's in a stronger position that the settlement's garrison and loyalty reaches a low enough level - a Rebellion will kick off.