Literally any person with eyeballs:
"Sir! We have the ability, with our current weapons and current conditions, to entirely remove this enemy force from the field, and annihilate them entirely; we can remove this threat completely, for the rest of our lives, just by leveling our Dragon Killing Ballistæ and firing them three times."
"Do you want us to completely end this war, save all of these civilians, rescue the kingdom, and prove yourself to your father?"
Fucktarded Author/Mangaka:
"No! We has to wun away! I'zs too scawwy! Wun away!"
Van, who has almost acted like a grown up a few times, has literally never acted like this, and it's really fucking stupid.
I do not understand what the fuck is wrong with this author, but this was the stupidest fucking thing I have read in a minute, and I dont get what the fuck this fucking idiotic moron thought makes sense about suddenly running away from troops in contact.
The follow-on forces will already be investing the city, making it impossible to retake; by allowing the forces to simply run after you, they can now return to the city and take control, so you have helped them quite a bit; nobody else can come to the aid of any defenders because you dropped trees in the road, effectively giving the city of Scudetto to the enemy.
The fact that they lost their dragons simply means they have to use their own catapults, or the ones left behind when you abandoned the city.
Van should be hung, publicly, for cowardice, and for abandoning the City of Scudetto and its people.