I think they explained it cuz the other party(her fiance) is involved that there may be an incursión or coup within the country from nobles that may happen
IIRC, after Almus sets up some stone fortresses at his border...
Some serfs from Diabelwhatever’s towns desert because of famine or unfair taxation. It’s supposed to be a death penalty if they flee, and to “harass” or fuck with Almus’s men on guard, they butcher the peasants... until they can’t take it anymore and intervene, causing a reason for Diabelwhatever to attack Almus.
Also salt mines...?
Or not. I think the LN/Manga is very different from the WN I read, and my memory’s bad and I could be thinking of a different, yet similar isekai since a lot of isekai have a ton of overlap.