Leave Age of Medieval running without touching anything and the map will still change. That is deliberate.
Houses fall out over real things: a raid, an embargo, a refused ultimatum. Two Houses can settle it between themselves in a private war. Or the matter climbs to their crowns, and it becomes a war of realms, with vassals marching for a quarrel that started two valleys away.
Wars end too, at a peace table, and land that was taken stays taken. In one test world that we let run for three years, settlements changed owner 93 times, with no player in it.
We do not hold wars back by hand to keep the map tidy. What limits a war is what limits it for you: food for the troops, coins for the pay, and a wall that somebody has to get through.
Age of Medieval is developed by UnderStudio in UnderStudio 2D and published by Brasa Interactive. It releases on 17 May 2027.
Official site: https://ageofmedieval.com/