Crossing the Rubicon

The phrase "crossing the Rubicon" is an idiom meaning "passing the point of no return". Its meaning comes from the crossing of the Rubicon river by Julius Caesar in January 49 BC at the head of the 13th Legion. Caesar was not allowed to command an army within Italy proper, and by crossing the river with his forces was defying law and risking death. The crossing precipitated a civil war, which eventually led to Caesar becoming dictator for life (dictator perpetuo). Caesar had previously been appointed governor of a region that stretched from southern Gaul to Illyricum. As his term was coming to an end, the Senate ordered him to disband his army and return to Rome. Caesar defied the order, and instead brought his army to Rome, occupying the city of Ariminum then crossing the Rubicon towards the south. The exact date of the crossing is unknown, but scholars usually place it on the night of 10 and 11 January because of the speeds at which messengers could travel at that time. The phrase alea iacta est ("the die is cast"), allegedly uttered by Caesar just before the crossing, also comes from this event.