A republic run by competing commanders
Rome did not become an empire in one move. For about a century before the first emperor, the Republic was shaken by quarrels between powerful individuals who commanded armies. Historians debate why, but one common explanation is that after centuries of Roman expansion, soldiers increasingly depended on their generals for pay, plunder and land when they retired. Loyalty to the state weakened, and loyalty to a commander grew. The offices and customs of the Republic stayed in place, but the men who held real power increasingly ignored their limits.
The sequence below follows that personal story from Sulla to Octavian. The constitutional machinery, including the role of the Roman Senate, matters too, but it was the choices of a few individuals that decided each crisis.
Sulla: the precedent
The rivalry between Gaius Marius and Lucius Cornelius Sulla set the pattern. In 88 BCE, when the Senate gave Sulla the command against King Mithridates of Pontus and a political faction tried to transfer it to Marius, Sulla marched his army on Rome itself. This was the first time a Roman commander is known to have done so. He later won the civil war that followed, and in 82 BCE had himself made dictator without a fixed term. He ordered proscriptions, lists of enemies who could be killed and whose property was confiscated, and he rewrote parts of the constitution to strengthen the Senate.
Sulla then did something unusual. He resigned the dictatorship, probably in 79 BCE, and died the following year. His reforms did not last long, but the precedent did: an army could be used to settle politics.
Pompey and Caesar
Gnaeus Pompeius, called Pompey, began his career as a young supporter of Sulla and won a reputation through campaigns in Spain, in the suppression of the slave rebellion of Spartacus, a revolt against Roman slavery, and against Mediterranean pirates in 67 BCE. In the 60s he reorganised Rome’s eastern territories, and his settlement made Syria a Roman province, with its capital at Antioch on the Orontes. He returned in 62 BCE and disbanded his army, but found that the Senate was reluctant to reward his veterans.
That frustration helped bring about an informal alliance in 60 BCE between Pompey, the wealthy Marcus Crassus and the ambitious Gaius Julius Caesar, now called the First Triumvirate by modern writers. Caesar, consul in 59 BCE, then took command in Gaul. The conquest of Gaul between 58 and about 50 BCE gave him wealth, a devoted army and enormous prestige. Meanwhile the alliance fell apart: Caesar’s daughter Julia, Pompey’s wife, died in 54 BCE and Crassus was killed fighting the Parthians at Carrhae in 53 BCE.
By 50 BCE the Senate, backed by Pompey, wanted Caesar to give up his command and return as a private citizen, where his enemies could prosecute him. On about 10 January 49 BCE, Caesar led a legion across the Rubicon, the boundary of his province, and began a civil war. Pompey left Italy, and Caesar defeated his forces at Pharsalus in Greece in 48 BCE. Pompey fled to Egypt, where he was killed. Caesar followed, became involved in the royal dispute in Ptolemaic Alexandria, and allied himself with Cleopatra VII.
Caesar’s dictatorship and the Ides of March
After further victories in Africa and Spain, Caesar held a series of dictatorships and finally, in early 44 BCE, was named dictator for life. He carried out reforms, including the calendar, and pardoned many enemies. His position still alarmed many senators, who feared the end of the old order. On 15 March 44 BCE, the Ides of March, a group of senators including Marcus Brutus and Gaius Cassius stabbed him to death. The assassins thought they were restoring the Republic. Instead they set off another round of civil wars.
Octavian and the first emperor
Caesar’s great-nephew Gaius Octavius, then about 18, learned that Caesar’s will adopted him. He took the name Caesar, gathered veterans loyal to the dead dictator’s memory, and entered politics. In 43 BCE he, Mark Antony and Marcus Lepidus formed the Second Triumvirate, a legal board with sweeping powers. Their proscriptions killed many opponents, including the orator Cicero.
The triumvirs defeated Brutus and Cassius at Philippi in 42 BCE, and then competed with each other. Octavian pushed Lepidus aside and defeated Sextus Pompey, Pompey’s son, at sea in 36 BCE. The final contest was with Antony, who had allied himself with Cleopatra. At the naval battle of Actium in 31 BCE Octavian’s fleet, led by Agrippa, won, and Antony and Cleopatra died in 30 BCE as Octavian entered Egypt.
Octavian now controlled the Roman legions and the treasury of Egypt, and he had no rival left. He was careful not to claim the title of king or dictator, which Romans distrusted. In 27 BCE he formally handed his special powers back to the Senate, which in turn gave him the honorific name Augustus. In practice he kept command of the main armies and the provinces where they were based, and he held other powers for life. The result, usually called the Augustan principate, was an autocracy dressed in Republican forms.
Why ambition mattered, and what it did not explain
The generals’ rivalries did not alone cause the Republic’s end. Land hunger, debt, rural change and the problems of governing a vast territory with city institutions all played a part. Even so, the personal stories matter, because each commander took a step that made the next one easier. Sulla marched on Rome, Pompey commanded beyond normal limits, Caesar crossed the Rubicon and Octavian turned victory into a settled system. The Republic’s offices continued under Augustus, but the question of who held power had been answered by force of arms.