From Caesar to Augustus

Less than a year later, Caesar was murdered by a group of his enemies (led by the republican nobles Marcus Junius Brutus and Gaius Cassius). Consul Mark Antony and Caesar's great-nephew and adopted heir, Octavian, joined forces to crush Brutus and Cassius and divided power in Rome with ex-consul Lepidus in what was known as the Second Triumvirate. With Octavian leading the western provinces, Antony the east, and Lepidus Africa, tensions developed by 36 B.C. and the triumvirate soon dissolved. In 31 B.C., Octavian triumped over the forces of Antony and Queen Cleopatra of Egypt (also rumored to be the onetime lover of Julius Caesar) in the Battle of Actium. In the wake of this devastating defeat, Antony and Cleopatra committed suicide.

By 29 B.C., Octavian was the sole leader of Rome and all its provinces. To avoid meeting Caesar's fate, he made sure to make his position as absolute ruler acceptable to the public by apparently restoring the political institutions of the Roman republic while in reality retaining all real power for himself. In 27 B.C., Octavian assumed the title of Augustus, becoming the first emperor of Rome.

Age of the Emperors

Augustus' rule restored morale in Rome after a century of discord and corruption and ushered in the famous pax Romana–two full centuries of peace and prosperity. He instituted various social reforms, won numerous military victories and allowed Roman literature, art, architecture and religion to flourish. Augustus ruled for 56 years, supported by his great army and by a growing cult of devotion to the emperor. When he died, the Senate elevated Augustus to the status of a god, beginning a long-running tradition of deification for popular emperors. 

Augustus' dynasty included the unpopular Tiberius (14-37 A.D.), the bloodthirsty and unstable Caligula (37-41) and Claudius (41-54), who was best remembered for his army's conquest of Britain. The line ended with Nero (54-68), whose excesses drained the Roman treasury and led to his downfall and eventual suicide. Four emperors took the throne in the tumultuous year after Nero's death; the fourth, Vespasian (69-79), and his successors, Titus and Domitian, were known as the Flavians; they attempted to temper the excesses of the Roman court, restore Senate authority and promote public welfare. Titus (79-81) earned his people's devotion with his handling of recovery efforts after the infamous eruption of Vesuvius, which destroyed the towns of Herculaneum and Pompeii.

The reign of Nerva (96-98), who was selected by the Senate to succeed Domitian, began another golden age in Roman history, during which four emperors--Trajan, Hadrian, Antoninus Pius, and Marcus Aurelius--took the throne peacefully, succeeding one another by adoption, as opposed to hereditary succession. Trajan (98-117) expanded Rome's borders to the greatest extent in history with victories over the kingdoms of Dacia (now northwestern Romania) and Parthia. His successor Hadrian (117-138) solidified the empire's frontiers and continued his predecessor's work of establishing internal stability and instituting administrative reforms.

Under Antoninus Pius (138-161), Rome continued in peace and prosperity, but the reign of Marcus Aurelius (161–180) was dominated by conflict, including war against Parthia and Armenia and the invasion of Germanic tribes from the north. When Marcus fell ill and died near the battlefield at Vindobona (Vienna), he broke with the tradition of non-hereditary succession and named his 19-year-old son Commodus as his successor.

Decline and Disintegration

The decadence and incompetence of Commodus (180-192) brought the golden age of the Roman emperors to a disappointing end. His death at the hands of his own ministers sparked another period of civil war, from which Lucius Septimius Severus (193-211) emerged victorious. During the third century Rome suffered from a cycle of near-constant conflict. A total of 22 emperors took the throne, many of them meeting violent ends at the hands of the same soldiers who had propelled them to power. Meanwhile, threats from outside plagued the empire and depleted its riches, including continuing aggression from Germans and Parthians and raids by the Goths over the Aegean Sea.

The reign of Diocletian (284-305) temporarily restored peace and prosperity in Rome, but at a high cost to the unity of the empire. Diocletian divided power into the so-called tetrarchy (rule of four), sharing his title of Augustus (emperor) with Maximian. A pair of generals, Galerius and Constantius, were appointed as the assistants and chosen successors of Diocletian and Maximian; Diocletian and Galerius ruled the eastern Roman Empire, while Maximian and Constantius took power in the west.

The stability of this system suffered greatly after Diocletian and Maximian retired from office. Constantine (the son of Constantius) emerged from the ensuing power struggles as sole emperor of a reunified Rome in 324. He moved the Roman capital to the Greek city of Byzantium, which he renamed Constantinople. At the Council of Nicaea in 325, Constantine made Christianity (once an obscure Jewish sect) Rome's official religion.

Roman unity under Constantine proved illusory, and 30 years after his death the eastern and western empires were again divided. Despite its continuing battle against Persian forces, the eastern Roman Empire–later known as the Byzantine Empire–would remain largely intact for centuries to come. An entirely different story played out in the west, where the empire was wracked by internal conflict as well as threats from abroad–particularly from the Germanic tribes now established within the empire's frontiers–and was steadily losing money due to constant warfare.

Rome eventually collapsed under the weight of its own bloated empire, losing its provinces one by one: Britain around 410; Spain and northern Africa by 430. Attila and his brutal Huns invaded Gaul and Italy around 450, further shaking the foundations of the empire. In September 476, a Germanic prince named Odovacar won control of the Roman army in Italy. After deposing the last western emperor, Romulus Augustus, Odovacar's troops proclaimed him king of Italy, bringing an ignoble end to the long, tumultuous history of ancient Rome.