You could also suggest another reason the population was concentrated, that was probably at work in the new world as well: if you’re the local aristocrat, and your job is to tax the peasants and muster them in wartime, it really helps to have them all in one place.
As for the Greeks, what’s funny is that they were hilariously bad at siege warfare. In almost 30 years of on and off warfare, neither Athens nor Sparta was ever seriously threatened until the very end. And while it’s totally dumb to compare a bronze age epic with actual history, let’s be real, the Romans would’ve finished off Troy in a month.
In these days of economic cold warfare, it's interesting to think of metropolitan areas as those settlements which have sufficiently-developed economies that they are resistant to single-factor speculative attacks (whether on a currency or an actual basket of goods). Internal economies would be the safest protection, as trade networks may or may not be useful, depending upon the relative interdiction capabilities of one's friends and foes.
see also https://en.wikipedia.org/wiki/First_League_of_Armed_Neutrali...
On a further tangent:
Because spain reached the philippines from one direction and portugal reached malacca from the opposite, dates in southeast asia were a day off from each other, depending upon colonising power. It is a logical truth that all babies born in the philippines on Tuesday, 31 Dec 1845 were neon green and spoke hebrew.
https://en.wikipedia.org/wiki/Inter_caetera https://en.wikipedia.org/wiki/Treaty_of_Tordesillas
https://webspace.science.uu.nl/~gent0113/idl/idl_philippines...
That's interesting. You can read about the European patterns as far back as classical Greece - when the season came, one city would gather some soldiers, go bust up the other city's fields, set up some triumph marker, and get back home ...