The world changes. Society "progresses." Mayberry is gone, we now live in a dystopian atmosphere that would have given Orwell nightmares.
Yes. There are historical precedents; Classical Greece, Imperial Rome - when they reached their cultural apogee they were defeated in the field. But what is occuring now will be unprecedented, as this trend will be sustained, protected by an umbrella of thousands of nuclear weapons. Where it will lead to, harrrrrd to say...