Reign of Augustus

The reign of Augustus as Rome's first emperor began in 27 BC with his first settlement with the Roman Senate, which granted him extraordinary proconsular powers, control over half of Rome's provinces and most of its armies, and the title of augustus ('the revered'). Prior to this event he is labeled by historians as Octavian (Latin: Octavianus), having been born Gaius Octavius, before adopting the name of his great-uncle Gaius Julius Caesar, who named him as his primary heir in his will. In 30 BC Octavian defeated fellow Roman triumvir Mark Antony and his wife Cleopatra, Queen of the Ptolemaic Kingdom, conquering Egypt and bringing it under his personal possession. Styling himself as princeps ('leading citizen', or 'first citizen'), Augustus sought to uphold the facade that he was a restorer of the Roman Republic, though his reign is viewed as the beginning of the Principate phase of the Roman Empire, which was ruled subsequently by members of his imperial family. After his death in AD 14, Augustus was deified and succeeded by his stepson and adoptive son Tiberius.

During his second settlement with the Roman Senate in 23 BC, Augustus resigned from the consulship and was not elected to this position again until 5 and 2 BC, so that he could help foster the political careers of his grandsons Gaius and Lucius Caesar. However, Augustus was granted the additional powers of the tribunate and censorship, holding these privileges for life and without formal election to either of these offices. He was granted authority to dictate affairs within the pomerium of Rome. Through his legates, he exercised direct control over provinces allotted to him by the Senate, but also interfered in the governance of provinces nominally controlled by the Senate through its proconsul governors. With the death of former triumvir Lepidus in 12 BC, Augustus assumed the title of pontifex maximus ('supreme pontiff'), head of Rome's College of Pontiffs. In 2 BC, the Senate also conferred on Augustus the title of pater patriae ('father of the country').

Augustus also conducted Rome's diplomacy. The Senate deferred to his decisions in the realm of foreign relations as he established peace treaties with the Parthian Empire in West Asia (to the east of Roman Syria) and the Kingdom of Kush in Northeast Africa (to the south of Roman Egypt). Augustus oversaw military campaigns in various regions. He completed the Roman conquest of Hispania with the Cantabrian Wars in the northern Iberian peninsula. In Southeastern and Central Europe, Augustus also ensured the Roman conquest and annexation of Dalmatia, Pannonia, Noricum, and Raetia. In Germania, Roman armies conquered as far as the Elbe River. However, with the defeat of Publius Quinctilius Varus by the forces of the Cherusci chief Arminius at the Battle of the Teutoburg Forest in AD 9, Augustus settled on defending the Rhineland as Rome's northern frontier.