In January 49 BC Julius Caesar, governor of Gaul, stood with a single legion beside the Rubicon, a small river that marked the border of Italy. The Senate had ordered him to give up his army. Crossing the river under arms would mean civil war.
According to the historian Suetonius, Caesar hesitated, then said: "The die is cast." His soldiers followed him across.
Rome's greatest general, Pompey, fled the city with much of the Senate. Within four years Caesar had defeated his rivals from Greece to Egypt to Spain.
