 According to some authors, he is said to have uttered the phrase ""alea iacta est""—the die is cast—as his army marched through the shallow river.Today, the phrase ""crossing the Rubicon"" is a metaphor that means to pass a point of no return.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 allies) to the south.