The Roman general who crossed the Rubicon River is Julius Caesar, marking a pivotal point in Roman history. In 49 BCE, his crossing signified defiance against the Roman Senate and led to a civil war. The phrase "crossing the Rubicon" has since become synonymous with making irreversible decisions. Caesar’s actions ultimately brought an end to the Roman Republic and led to his rise as a dictator, which transformed the governance structure of Rome. This event played a crucial role in the establishment of the Roman Empire and altered the course of Western history.