[jwdunne]

That's an interesting question I've thought a lot about in the past (the rise of the great empires in general, to be honest).

My best guess is that they were able to do this thanks to the advancement required to face off the threads before their eventual rise. There wasn't anybody who could really compete with what they had after those wars were won. The Pax Romana held relative peace in Europe because of that strength.

I'd love someone with more knowledge on the subject to come and answer this - really fascinating subject.

[jwhitlark]

A lot of Roman strength was organizational. In conquering, they spread that knowledge. It would probably have been hard to do it again with the same technique.