When did Julius Caesar cross the Rubicon River?

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Statue of Julius Caesar in Roman military attire stands in front of a domed building in Rome, Italy, with a clear blue sky in the background. — Julius Caesar Julius Caesar, bronze sculpture in Rome.

Julius Caesar crossed the Rubicon River on January 10–11, 49 BCE.1

By leading his troops across this small stream, which served as the boundary between his province of Cisalpine Gaul and Italy, Caesar violated the law that prohibited a general from bringing an army into Italy. This act of defiance effectively declared war against the Roman Senate, initiating a civil war that ultimately led to Caesar becoming the undisputed ruler of the Roman world.213