I think the author gave some hints here. An objective turning these barbarian people to gentle noble is just a cover. No matter how much the 8th battalion soldiers make merits on battlefield, if they cause a havoc/harming the bystanders on peaceful era accidentally or not, gives the royal family an excuse to terminate them
Someone please give me link to read novel. I couldn't find it anywhere ╥﹏╥
not sure if you still need it but heree:
https://www.novelupdates.com/series/the-villainess-captured-the-grand-duke/?grr=1
Lol he just plant a flag there (⊙…⊙ )