Anons, when it comes.to the border, there is a semi lethal weapon. I say semi because it can be demonstrated without hurting anyone, unless they step across the border.
Flamethrowers.
Inspires great fear, too. Instinctual, unlike other weapons.
This is an invasion. Read how the flame throwers worked in the Pacific for dug in Japanese. Many surrendered rather than be burned out.
My first reaction would be napalm the lot, then fire bomb any city that helped them on the route. Good thing I'm not in charge. Kek! This is still, however, an act of war, whether you wish to call it such or no.