Rubicon

The Rubicon (Rubico) is an ancient Latin name for a small river in northern Italy. In Roman times it flowed into the Adriatic Sea between Ariminum[?] and Caesena[?]. The actual modern identity of the water-course is uncertain, it is usually identified as the Pisciatello in its upper reaches and then the Fiumicino to the sea.

The river is notable as Roman law forbade any general from crossing it with a standing army. The river was considered to mark the boundary between the Roman province of Cisalpine Gaul[?] and the Roman heartland, the law thus protected the republic from internal military threat.

When Julius Caesar crossed the river in 49 BCE, supposedly on January 10, in pursuit of Gnaeus Pompeius Magnus he broke that law and made armed conflict inevitable, the die was cast (iacta alea est) as Caesar is said to have remarked. As Suetonius describes the scene Caesar was apparently still undecided as he approached the river and Suetonius gave credit for the actual moment of crossing to the appearence of a supernatural apparition.

The phrase "crossing the Rubicon" has survived to refer to any person committing themselves irrevocably to a risky course of action.