Under the Reign of Augustus, the Roman empire shifts from a republic to an empire with a more centralized government under the leadership of an Emperor. Its from this period of about 27 BC to 200 AD that the empire reaches its greatest extent stretching from Britannia all the way to the Persian Gulf. This is more of an overview of the era and the emperors who led the empire. None the less, a super interesting period in history and one of the greatest empires in history!