There are certain historical events that have a significance beyond the immediate fact that they happened, and Caesar’s action in crossing a tiny river is one of them.
After years of war in Britain and Gaul, Caesar had decided to become master of Rome. But, at the time, Pompey ruled. Pompey saw Caesar (as Caesar saw him) as a rival, and feared the acclaim Caesar had acquired for his great military victories. Pompey ordered Caesar to disband his army and send his soldiers home, since he had succeeded in subduing Gaul.
But Caesar had other plans. He marched his army to the banks of the Rubicon, the southern boundary of Gaul. One step over this line would be a declaration of war on Pompey and his government. We pick up the action in Famous Men of Rome:
Cæsar halted his army at the Rubicon and forbade anyone to cross it until he gave the order. He stood for some time on the banks in deep thought as if trying to decide whether he should cross the river and proceed or give up his dangerous undertaking. He was still within his own territory as commander of Gaul; if he should cross the Rubicon he would be on territory directly under the government of the officers at Rome. By law it was an act of treason, punishable by death, for any Roman general to enter this territory with an army without permission from the Senate.
“We can retreat now,” said Cæsar to some of his officers who stood near him, “but once across the Rubicon it will be too late to draw back.”
While Cæsar was talking, a shepherd came along from a field close by, playing lively music on a reed pipe. The soldiers gathered around him to listen to the music, and some of them began to dance. One of Cæsar’s trumpeters stood among the soldiers with his trumpet in his hand. The shepherd saw the trumpet, suddenly seized it, and walked to the bridge over the Rubicon, which was but a few steps off. Then he put the trumpet to his lips, sounded the stirring notes for an advance of the troops, and began to march across the bridge.
“The die is cast,” Caesar is said to have declared. Caesar marched on Rome unopposed, Pompey fled, and the city fell easily into his hands.
The significance of the physical act of crossing the Rubicon was that it signaled a declaration of war. The “die was cast” because, there was no going back. He was committed.
Today, we use the expression “crossing the Rubicon” as a way of describing a decisive act, one that commits us to doing something we will not be able to undo.
You can read more about these events in Memoria Press’ Famous Men of Rome and in The Book of the Ancient Romans. Both have study guides, quizzes and teacher’s manuals and are part of MP’s classical studies program.