this is my issue with this series.
all the tactics when they can just throw in the nuke and be done with it.
even if their tactics fails they can just throw in their nuke like Ike or the demon king to make tactics not even matter, even their top mage can beat the hero's party alone so like legit can't the demon king just solo the verse and be done with this.
the author could have easily made them powerful but not powerful enough where they can solo a whole corps of a standing army. I mean the only reason why they did the dragon thing is to give the demon king a cool entrance, she could have just teleport in the middle kill the dragon and everyone and not waste gunpower and not use the magic mirror device.