How did the Roman Empire rise to power?
The Roman Empire came, sadly, out of the slow decay of the Roman Republic. The transformation was subtle and long-term; the key reason appears to be that the Roman Constitution was designed for the governance of Rome and her environs, and was undermined over time as Rome began to conquer overseas territories. The office of "Tribune of the People" became the key office in exploiting the spoils of foreign countries; factions vying for that office became corrupt in its attainment and execution. Because of the infighting and political stagnation, eventually one man consolidated enough power to become Emperor. Considering the United States in the world today and its disregard for its founding documents and focus on the all-powerful Office of the President, one can't help be struck with the similarities, and how history repeats itself, and if, in fact, the American Republic founded only a few hundred years ago is now the American Empire. See a more detailed history of the Late Roman Republic at the link:
The Roman Empire became a powerful ancient civilization first because of location and resources. Italy being located right on the Mediterranean Sea and sandwiched between other powerful civilzations gave it a great abundance of resources and strength. Also great leaders such as Julius Caesar that started to build Rome as a great city and empire by also focusing on military strength in order for Rome to conquer other great civilizations such as the Ottoman Empire. Then you Have Augustus Octavian who brought Rome to a Golden Age, or Pax Romana. This was a time when the Colosseum was built and there was peace among the whole empire. Location, resources, and great leaders all contributed to the rise of the great Roman Empire.
One key to its success was the "join the club" policy. Once taken by force, conquered people were entitled to a 'second-class' Roman citizenship, with partial rights and privileges (know as 'the Latin Right'). This discouraged insurrection of newly conquered territories and reinforced coorperation and adhesion to the group:
The granting of citizenship to the conquered and the allies was a vital step in the process of Romanization. This step was one of the most effective political tools and (at that point in history) original political ideas (perhaps one of the most important reasons for the success of Rome).