I think Army Cohesion should go up if you encounter an enemy army of similar size (within 100 men) by up to 30%. And get a 5-10% increase for each fief that is taken (aka successful siege).
Engineering should level from siege weapons doing their thing, and relations should go up by a few points for all those who participated in a successful siege in an army you lead, showing you're a competent leader etc.
Engineering should level from siege weapons doing their thing, and relations should go up by a few points for all those who participated in a successful siege in an army you lead, showing you're a competent leader etc.