Definition: To commit to an irreversible course of action; the point of no return; making a final decision
Variants: to cross the Rubicon
Origin: Historian Plutarch in his biographical work, Plutarch’s Lives (c. 110 AD), recounts the story that led to this famous phrase. In 50 BC, the Roman Senate led by Pompey, ordered Julius Caesar, who was the governor of Gaul, to disband his army (he commanded four legions) and return to Rome since his term was completed. Caesar was fearful of being prosecuted should he return to Rome without the immunity given to magistrates. On January 1, 49 BC, Pompey persuaded the Senate to declare Caesar an enemy of the state and ordered him to return to Rome for a trial. Two of Ceasar’s loyal men traveled 250 miles to let Caesar know what Pompey had orchestrated. When he heard the news, Caesar uttered the famous phrase, “The die has been cast.” Caesar assembled his forces and marched toward Rome. They reached the River Rubicon, which separates Rome and Gaul, in mid-January. As he reached the river banks, Casesar turned to his army and said, “Even now we may draw back, but once across that little bridge, the whole issue is with the sword. Take we the course which the signs of the gods and the false dealing of our foes point out?” When his soldiers roared their approval, he responded, “Let the die be cast” — in other words, “let’s go for broke.” Caesar easily defeated Pompey and his forces in the resulting civil war, becoming the greatest leader of the Roman Empire until his assassination in 44 BC.
For further reading: Sticklers, Sideburns & Bikinis: The Military Origins of Everyday Words and Phrases by Graeme Donald, Osprey Publishing (2008).
Lives of Noble Grecians and Romans by Plutarch, Modern Library (1992).