Augustus (originally Octavian) is arguably the single most important figure in Roman history. In the course of his long and spectacular career, he put an end to the advancing decay of the Republic and established a new basis for Roman government that was to stand for three centuries. This system, termed the "Principate," was far from flawless, but it provided the Roman Empire with a series of rulers who presided over the longest period of unity, peace, and prosperity that Western Europe, the Middle East and the North African seaboard have known in their entire recorded history. Even if the rulers themselves on occasion left much to be desired, the scale of Augustus's achievement in establishing the system cannot be overstated. Aside from the immense importance of Augustus's reign, he himself is an intriguing figure: at once tolerant and cruel, ruthless and forgiving, shameless and considerate.

Early life:

Octavian was born in the city of Rome on 23 September 63BC. He was given the name Gaius Octavius Thurinus. His mother Atia was the niece of Julius Caesar. In 59BC, when he was four years old, his father died. His mother married a former governor of Syria, Lucius Marcius Philippus. Philippus claimed descent from Alexander the Great, and was elected consul in 56BC. Philippus never had much of an interest in young Octavian. Because of this, Octavian was raised by his grandmother (and Julius Caesar's sister), Julia Caesaris.

Caesar’s Death

At the time Caesar was killed on the Ides of March (the 15th) 44BC, Octavian was studying and undergoing military training in Illyria (present day Albania). Rejecting the advice of some army officers to take shelter with the troops in Macedonia, he sailed to the Italian peninsula to learn if he had any potential political fortunes or security left to him as an inheritance. After landing on the Italian peninsula, he learned the contents of Caesar's will, which named him as Caesar's political heir as well as heir to two-thirds of his estate. Having no living legitimate children, Caesar had adopted his great-nephew Octavian as his son and main heir. Upon his adoption, Octavian assumed his great-uncle's name, Gaius Julius Caesar.

At the same time, Mark Antony (Marcus Antonius), Caesar's chief lieutenant and best friend, had taken possession of Caesar’s legal papers and assets and had expected that he himself would be the principal heir. Arriving in Rome on 6 May 44BC, Octavian found Mark Antony granted amnesty to Caesar’s assassins – chiefly Marcus Junius Brutus and Gaius Cassius Longinus (familiarly known as Brutus and Cassius).

Winning the Support of the Roman People

Octavian celebrated public games, instituted by Caesar, to ingratiate himself with the city’s people. He also succeeded in winning considerable numbers of the dictator's troops to his own allegiance. While Octavian’s popularity was on the rise, public opinion in Rome turned against Mark Antony. Antony attempted to pass laws which would lend him control over Gaul (present day France), but the Senate refused to comply. Octavian, meanwhile, built up a private army in Italy by recruiting Caesar’s veterans, and on 28 November persuaded two of Antony's legions to join his troops with the enticing offer of monetary gain. In the face of Octavian's large and capable force, Antony saw the danger of staying in Rome, and fled to Gaul where he attempted to seize power from the Roman government located there.

The Senate then called upon Octavian for aid, granting him the rank of senator in spite of his youth. Octavian’s soldiers forced the Senate to confer a vacant consulship on him and in doing so provided that Octavian would be sole consul. On April 43BC, Antony's forces were defeated by Octavian in two battles, forcing Antony to retreat.

Realized that forming an alliance would be far more beneficial than ongoing strife, Octavian soon reached an agreement with Antony and with another of Caesar's principal supporters, Lepidus, who had succeeded Caesar as chief priest. On November 27, 43 BCE , the three men were formally given a five-year dictatorial appointment as the Second Triumvirate—the first having been the informal compact between Pompey, Crassus, and Julius Caesar.

The Second Triumvirate

The new Triumvirate drew up a list of “proscribed” political enemies, and the consequent executions included 300 senators and 2,000 other patricians. Two of those political enemies were Brutus & Cassius, the chief architects of Julius Caesar’s assassination. Following Caesar’s murder, both Cassius and Brutus fled to the east and were located in Greece.

After forming the Second Triumvirate, Octavian and Antony crossed the Adriatic and, under Antony's leadership (Octavian being ill), won the two battles of Philippi against Brutus and Cassius, both of whom committed suicide. Antony, the senior partner, was allotted the east (and Gaul). Octavian secured Africa and Sicily, while Lepidus took control of Spain.

Like the First Triumvirate, the Second Triumvirate was ultimately unstable and could not withstand internal jealousies and ambitions. Antony detested Octavian and spent most of his time in the East, while Lepidus favored Antony but felt himself obscured by both his colleagues, despite having succeeded Caesar as the chief priest in 43 BC. As a result of his clear insecurities, Lepidus betrayed Octavian by foolishly attempting to seize control of Octavian's legions. Octavian unilaterally expelled Lepidus from the Triumvirate, but allowed him to retain his Pontificate.

The End of the Triumvirate

Despite having married Octavia, Octavian's sister, in 40 BC, Antony openly lived in Alexandria with Cleopatra VII of Egypt, even siring children with her. A master of propaganda, Octavian turned public opinion against his colleague.

When the Triumvirate's second term expired in 33 BC, Antony continued to use the title Triumvir; Octavian, opting to distance himself from Antony, refrained from using it. Octavian illegally obtained Antony's will in July 32 BC, and exposed it to the Roman public: it promised substantial legacies to Antony's children by Cleopatra, and instructed that his body should be shipped to Alexandria for burial. Rome was outraged, and the Senate declared war against Cleopatra, an important distinction because Octavian did not want the Roman people to consider it a civil war.

Octavian's forces decisively defeated those of Antony and Cleopatra at the Battle of Actium in Greece in September 31 BC, chasing them to Egypt in 30 BC. Both Antony and Cleopatra committed suicide in Alexandria, and Octavian personally took control of Egypt and Alexandria (Egyptian chronologies consider Octavian as Cleopatra's successor as Pharaoh). A conspiracy organized by Lepidus's son was crushed by Octavian. With the complete defeat of Antony and the marginalization of Lepidus, Octavian, having restyled himself "Augustus", was left sole master of the Roman world, and proceeded to establish the Principate as the first Roman "emperor".