Rome was able to gain its empire in large part by extending some form of citizenship to many of the people it conquered. Military expansion drove economic development, bringing enslaved people and loot back to Rome, which in turn transformed the city of Rome and Roman culture.
Rome became the most powerful state in the world by the first century BCE through a combination of military power, political flexibility, economic expansion, and more than a bit of good luck. This expansion changed the Mediterranean world and also changed Rome itself.
