Rubicon - History

History

During the Roman republic, the river Rubicon marked the boundary between the Roman province of Cisalpine Gaul to the north-east and Italy proper (controlled directly by Rome and its socii (allies)) to the south. On the north-western side, the border was marked by the river Arno, a much wider and more important waterway, which flows westward from the Apennine Mountains (its source is not far from Rubicon's source) into the Tyrrhenian Sea. Governors of Roman provinces were appointed promagistrates with imperium (roughly, "right to command") in their province(s). The governor would then serve as the general of the Roman army within the territory of his province(s). Roman law specified that only the elected magistrates (consuls and praetors) could hold imperium within Italy. Any promagistrate who entered Italy at the head of his troops forfeited his imperium and was therefore no longer legally allowed to command troops.

Exercising imperium when forbidden by the law was a capital offence, punishable by death. Furthermore, obeying the commands of a general who did not legally possess imperium was also a capital offence. If a general entered Italy whilst exercising command of an army, both the general and his soldiers became outlaws and were automatically condemned to death. Generals were thus obliged to disband their armies before entering Italy. In 49 BC, supposedly on January 10 of the Roman calendar, G. Julius Caesar led one legion, the Legio XIII Gemina, south over the Rubicon from Cisalpine Gaul to Italy to make his way to Rome. In doing so, he (deliberately) broke the law on imperium and made armed conflict inevitable. According to the historian Suetonius, Caesar uttered the famous phrase ālea iacta est ("the die has been cast"). Caesar's decision for swift action forced Pompey, the lawful consuls (G. Claudius Marcellus and L. Cornelius Lentulus Crus), and a large part of the Roman Senate to flee Rome in fear. Caesar's subsequent victory in Caesar's civil war ensured that punishment for the infraction would never be rendered.

Suetonius's account depicts Caesar as undecided as he approached the river, and attributes the crossing to a supernatural apparition. The phrase "crossing the Rubicon" has survived to refer to any individual or group committing itself irrevocably to a risky or revolutionary course of action, similar to the modern phrase "passing the point of no return".