Julius Caesar was a Roman general, statesman, Consul, and notable author of Latin prose. He played a critical role in the events that led to the demise of the Roman Republic and the rise of the Roman Empire. Caesar's conquest of Gaul, completed by 51 BC, extended Rome's territory to the English Channel and the Rhine. With the Gallic Wars concluded, the Senate ordered Caesar to lay down his military command and return to Rome. Caesar refused, and marked his defiance in 49 BC by crossing the Rubicon with a legion, leaving his province and illegally entering Roman territory under arms. Civil war resulted, from which he emerged as the unrivaled leader of Rome.