You cannot solve problems by killing people on mass. Making war even cheaper will certainly not help.
Oh but you can, you just need to do it thoroughly and brutally, ie the way things were done historically.
There would be no refugees fleeing if there were no refugees left.
No refugees would flee a warzone where they risk death to enter an enemy territory where they faced almost certain death at the hands of an organised military force.
Insurgents could not hide amongst civilian populations if the rulers were willing to systematically wipe out civilians until the insurgency stopped.
A lack of morals and a willingness to do whatever necessary is a significant advantage in any war.