I started writing this in January and sort of got stuck on it, along with some other things going on. I’m writing here to sort my thoughts out about something, so it may not be the most coherent.
City-fortresses don’t really exist anymore. If they did, what might they look like? Why would anyone want one?
Bottom Line
Fortifying the city as-is will require billions of dollars, a reserve system, and would probably create a tradeoff between mass resettlement and maintaining accustomed levels of economic activity. Two historically novel problems are the volume of traffic required for commerce and the threat of stand-off attack. The fortress would have no strategic depth to mitigate the effects of air and missile attacks, which are much easier to carry out on the margin than even in the mid-20th century.