Defense economics will prevent this transition to city-states from happening.
Emerging defense technologies like drones, lasers, robots, micro-scale manufacturing, and self-driving vehicles - along with the latest generation of existing weaponry like MANPADS and anti-tank missiles - all preference the defender. They allow a group of relatively untrained and loosely organized defenders who know the terrain well to deploy extremely effective resistance against an attacker, as long as it's at short range. A drone swarm can quite literally destroy all hostile forces within an area without risking a single person, but it can't do this beyond say 100 miles out. These technologies are all for defense, not power-projection.
This has a similar effect as the development of the musket in the 1500s. The musket allowed relatively untrained militias to enjoy superior firepower over the knights and longbowmen that had trained professionally their whole lives. As a result, smaller city-states and colonies could defend themselves against the large standing armies that kings and emperors could wield, and so the feudal system collapsed. This reversed with rifles (their greater accuracy benefitted from more professional training) and modern armor & explosives (which required an industrial base and supply chain greater than any city could muster), ushering in the era of nation-states. Military technology is changing again, and that's why I believe the nation-state system is again going to revert to smaller decentralized units.
> They allow a group of relatively untrained and loosely organized defenders who know the terrain well to deploy extremely effective resistance against an attacker, as long as it's at short range. A drone swarm can quite literally destroy all hostile forces within an area without risking a single person, but it can't do this beyond say 100 miles out.
We already have this "drone swarm", we just call it a guided missile.
The hard part in fighting a modern army isn't killing them, it's finding them. The defender is inherently at a disadvantage in this regard because they have things to defend, which necessitate that they're position in the vicinity. Russia is struggling at the moment not because defenders are inherently advantaged but because they're relying on conscripts and relatively untrained soldiers.
> The musket allowed relatively untrained militias to enjoy superior firepower over the knights and longbowmen that had trained professionally their whole lives. As a result, smaller city-states and colonies could defend themselves against the large standing armies that kings and emperors could wield, and so the feudal system collapsed.
The exact opposite of what you're describing happened with the wide utilization of gunpowder. Pre-gunpowder, city-states and small kingdoms enjoyed relative independence due to the sheer expense of penetrating walls. Post-gunpowder, artillery (not rifles) required a whole professional organization to be utilized effectively, and formed the backbone of the army, so small states could no longer field or effectively defend against larger states, leading to increased centralization of authority, well before the creation of nation-states. "Makers of Modern Strategy from Machiavelli to the Nuclear Age" covers this transition pretty extensively.
Yes; this, and all of NATO is assisting Ukraine with G-2 (intelligence) and G-4 (logistics).
In other words, Russia created a military that was bad at being a military.
The only good thing that will come of this conflict is a revitalization in the study of military arts.
Changing topic: you said upthread “[people are] vastly underestimating the difficulty of bringing a complex system like the economy up from a cold start. In my experience with complex systems that are much less complex than the economy, it can't be done.”. Your personal example is irrelevant because it is a single person trying to restart an economy. Cities recover after earthquakes (my city Christchurch 2010) and wars (I have visited ex-Yugoslavia) due to many independent actors working, perhaps not so much due to your “command economy” example. Capitalist individuals route around damage. Although I admit effective centralised government helped Christchurch recover quickly.