Crossing the Rubicon

The idiom "Crossing the Rubicon" means to pass a point of no return, and refers to Julius Caesar's army's crossing of the Rubicon River (in the north of Italy ) in 49 BC, which was considered an act of insurrection and treason. Julius Caesar uttered the famous phrase "alea iacta est"—the die is cast—as his army marched through the shallow river.