The first two centuries of the Empire saw a period of unprecedented stability and prosperity known as the Pax Romana 'Roman Peace'. Octavian's power then became unassailable, and in 27 BC the Roman Senate formally granted him overarching power and the new title Augustuseffectively making him the first Roman emperor. The following year Octavian conquered Ptolemaic Egyptending the Hellenistic period that had begun with the conquests of Alexander the Great of Macedon in the 4th century BC. The predecessor state of the Roman Empire, the Roman Republic which had replaced Rome's monarchy in the 6th century BC became severely destabilized in a series of civil wars and political conflicts.
Although fragmented briefly during the military crisis, the empire was forcibly reassembled, then ruled by multiple emperors who shared rule over the Western Roman Empire based in Milan and later in Ravenna and over the Eastern Roman Empire based in Nicomedia and later in Constantinople. From the accession of Caesar Augustus to the military anarchy of the third centuryit was a principate with Italy as metropole of the provinces and the city of Rome as sole capital 27 BC - AD.
As a polity it included large territorial holdings around the Mediterranean Sea in EuropeNorth Africa and West Asia ruled by emperors.
