Crossing the Rubicon
Julius Caesar's crossing the Rubicon river on 10 January, 49 BC precipitated the Roman Civil War, which ultimately led to Caesar's becoming dictator and the rise of the imperial era of Rome. Caesar had been appointed to a governorship over a region that ranged from southern Gaul to Illyricum (but not Italy). As his term of governorship ended, the Roman Senate ordered Caesar to disband his army and return to Rome. He was explicitly ordered not to take his army across the Rubicon river, which was at that time a northern boundary of Italy. In January 49 BC, Caesar brought the 13th legion across the river, which the Roman government considered insurrection, treason, and a declaration of war on the Roman Senate. 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.