Well what’s true about urban warfare is you can fortify prepared positions against bullets and use local knowledge and interior lines well enough that the defender’s at a huge advantage if you’re limited to small arms. You’d want air support or artillery, howitzers at least. Maybe you could do it with support weapons or explosive charges for breaching, but that’s very expensive in time and men, and explosives aren’t just lying around anymore. (Tannerite?)
I’m thinking of Vienna in the Austrian Civil War, the Karl-Marx-Hof housing development that leftists held against trained soldiers. Until they brought cannons in.
Which is the thing, when you line up your logistics and your politics (in a civil war, the besieger often starts off wanting to capture intact) to the point where you have heavy weapons, things change.
The MOVE bombing in Philadelphia - that was a group that had fortified their base, which was in a rowhouse block with party walls that could be tunneled through, and explicitly planned a dramatic final stand, but the Philly police had the logistical and political support to bring in a helicopter and bombs and they won it in a rout.
Guernica, you remember the Picasso painting, that’s from the Spanish Civil War, that’s a thing a right-insurrection pulled against a left-held town when it got bomber planes and worked up a “gloves are off” ideology.
The Siege of Sarajevo, that went on for years and there was hostile artillery in the hills encircling the town, but the New World Order crimped the besiegers’ materiel supply, denied airspace, and resupplied the city with UN convoys, you’d need US or Russian government patronage to pull that off.
The food supply - yeah, on one hand the just-in-time supply system cuts down stocks but from the French and Russian Revolutions we know cities are perfectly capable of fielding expeditionary forces of sufficient mass to seize food from more thinly populated areas.
(when it looked like Trump was going to lose and things might get rough in that direction, I looked up the location of nearby distribution centers, not the worst idea)
On the other hand, the idea that rightist forces would be able to lay sieges on cities strong enough to contain breakout attempts, long enough to force submission, prevent resupply by air or sea, either prevent reinforcements from elsewhere from breaking the siege or siege all leftist centers simultaneously while holding off any external intervention, but at that point we’re still talking militia guys with ARs and not an actual military, what scenario is that?
Re: The besieger still wanting to capture intact: I want to stress that’s most common in cases where the idea of you winning militarily is utterly ridiculous, at least for cases like the MOVE bombing anyway- where I should note the entire thing was handled by the Philadelphia police rather than the U.S. military, and even then the police used much less force than they could potentially have sued. I think this bears stressing because while a civil war is very unlikely, tiny groups who murder a handful of random police officers and maybe some civilians before getting themselves killed happen all the time and will continue to happen.
But more importantly, seconding the last sentence; we’re very unlikely to have a true civil war which comes down to grassroot leftists vs. grassroot rightists; any even slightly possible situations would be one or the other rising against the U.S. government- and would probably lose eventually. I could maybe see a situation in which a big chunk of the military splits off, which… would get pretty bad, probably in new and interesting ways that have never been seen before. The only way I could really picture that happening though if a president openly suspended the constitution and declared themselves King.