Julius Caesar Crosses the Rubicon

The event

For nearly a decade, Julius Caesar had built an extraordinary reputation and a fiercely loyal army through his conquest of Gaul. Back in Rome, though, his political rivals in the Senate — backed by his former ally Pompey, with whom Caesar had once shared power in an informal arrangement called the First Triumvirate — grew alarmed at his growing strength and ordered him to disband his army and return to Rome as a private citizen, stripped of his command.

Caesar refused. Roman law forbade any general from bringing an army across the Rubicon, a small river marking the boundary between his province and Italy proper; to cross it under arms was to declare war on the Republic itself. Caesar crossed anyway, reportedly declaring 'alea iacta est' — 'the die is cast' — and marched on Rome.

The resulting civil war between Caesar and Pompey's forces raged across the Mediterranean for years, but its decisive battle came quickly, at Pharsalus in Greece in 48 BC, where Caesar's smaller, hardened army routed Pompey's larger force. Pompey fled to Egypt, where he was murdered on arrival, and Caesar was left the master of the Roman world — though, as the next events in Rome's story show, not for long, and not without enormous consequences for the future of the Republic.

Other witnesses

• Suetonius, Life of Julius Caesar 31-35
• Caesar, Commentaries on the Civil War