by francopoli

On 10 January 49 BC, leading one legion, the Legio XIII Gemina, General Julius Caesar crossed the Rubicon River, the boundary between the Cisalpine Gaul province to the north and Italy proper to the south, a legally proscribed action forbidden to any army-leading general. The proscription protected the Roman Republic from a coup d'état; thus, Caesar's military action began a civil war.

This act of war on the Roman Republic by Caesar led to widespread approval amongst the Roman civilians, who regarded him as a hero. The historical records differ about which decisive comment Caesar made on crossing the Rubicon: one report is Alea iacta est (usually translated as "The die is cast").