Rome had defeated her great rival Carthage and overcame a slave revolt led by Spartacus, but these victories came at a price. Army generals who could deliver foreign conquests accumulated enormous amounts of power. Julius Caesar, seeking glory, would challenge the very existence of the republic. Join historian Bettany Hughes in an exploration of the momentous day in 49 B.C. when Caesar crossed the Rubicon River, violated Roman law, and heralded the transformation of the Roman Republic into an empire ruled by a single man.