Rubicon

Rubicon, Italian stream, famous for the crossing made by Julius Caesar in 49 B.C. As commander of Roman troops in Gaul, Caesar crossed this stream—once the border between Rome and Gaul—in reaction to the order for him to give up his power. Today the saying “to cross the Rubicon” indicates that something irreversible has occurred. In 49 B.C. this crossing eventually led to the rule of Rome by Julius Caesar.

See also: Caesar, (Gaius) Julius.