Roman Empire

From 27 BC Rome and its territories were ruled by a series of emperors, beginning with Augustus. By the 2nd century AD the empire covered about 13 million square kilometers (5 million square miles), with an estimated population of 55 million. Rome's main aims were to maintain peace in the empire and to extract money and other resources, mostly through taxation. The empire was administered as a series of provinces. Local elites became increasingly important and were given administrative posts: by the 3rd century AD they had become highly Romanized. In the 3rd and 4th centuries the empire declined through internal conflict and external threat, especially from Germanic peoples, including the Visigoths, Franks, Vandals and Ostrogoths. From the late 3rd century the eastern and western halves of the empire were usually ruled separately. After the sacks of Rome the city was occupied by Germanic invaders in the 5th century. The eastern empire survived and was gradually transformed into the medieval Byzantine empire.