For most of history, if a city was under siege, they had to be on high alert for sappers, mining under the walls, where they would place explosives. So they would listen to the ground, and when they heard sounds down there, would countermine to meet the enemy sappers & hopefully stop them from completing their mission. Fighting might occur underground.

If we consider possible tunnel fighting in the present day, one could visualize not only in-your-face combat in the tunnels, using state of the art weaponry, including robots/droids/drones to carry explosives forward (either anti-personnel or tunnel collapsing ordnance), then one should consider the theoretical use of tunnel boring machines in combat. Each side with the possibility of outflanking the enemy–maybe with an entire fleet of borers–and coming up in the tunnel to their rear. Also the use of fleets of "hunter seekers", as shown in Dune. And who knows what EDs (or other lethal devices) might have been embedded in the walls for remote use against oncomers. A fight of controlled chaos, danger on all sides, plus above and below. Can also believe that the sith/reptiles/demons would be using human shields.

>>8818308 The pussified commie guvs will be forced to accelerate, because the poor souls in those states will see the rest of the country back at it, making money, recreating, marrying, etc. No way, no how is that crap going to stand when they look across the state line at that and say, "WTF are we doing?"

>>8818836 Consider that POTUS has the power. Extreme power, under state of emergency throughout the land. And yet the man knows that the less it appears he is heavy handed, the better. Truth. So he is 2 steps ahead of those fuckers, as always, forcing them to do things against their will, things he can correctly deny having ordered. If any state or territory's populace gets pissed about their situation (they will), they will have to take it up with their commie overlords. Life is good.