Crossing The Rubicon: Inside The Meaning Of This Famous Idiom That Dates Back To Ancient Rome

Published July 12, 2023
Updated July 13, 2023

When Julius Caesar committed an act of war by crossing the Rubicon River and moving into Roman territory in 49 B.C.E., he gave birth to a classic phrase meaning that one has passed the point of no return.

Crossing The Rubicon

Wikimedia CommonsHistory of Julius Caesar by Jacob Abbott c. 1849.

On January 10, 49 B.C.E., Julius Caesar and his army crossed the Rubicon, a stream separating Gaul from the Roman Republic. This action would prompt a civil war in Rome that led to Caesar gaining power over the region and establishing the Roman Empire.

Today, the idiom “crossing the Rubicon” is a way to express that someone is passing the point of no return. It is an homage to the historic event that remains one of the most pivotal moments in Roman history.

The Story Of Julius Caesar And His Rise To Power

Julius Caesar

Public DomainPainting of Julius Caesar and his followers after crossing the Rubicon.

Before becoming one of the most famous leaders in Roman history, Julius Caesar served as governor of Gaul, an area broadly covering modern-day France.

Under his military leadership, Caesar expanded the borders of the Republic to include modern-day France, Spain, and Britain. He built quite a name for himself, and members of the Senate back in Rome became worried about his growing influence and power.

The root of this fear is the possibility that Caesar would march into Rome with his army. This, of course, would be an act of war, but would also ensure that Caesar maintained his power if he were successful.

The Roman Republic expected Caesar to relinquish control over his forces upon the completion of his gubernatorial role, but Caesar desperately wished to maintain power.

According to Roman law, a governor of a Roman province held authority over the territory and acted as the general of that region’s military forces. Any governor who entered Italy with his forces forfeited his right to be governor and command troops.

Not only was it punishable by death for a governor to enter Italy with troops, but it was also punishable by death to follow the orders of a governor who lost his right to govern.

Caesar did not take a decision lightly, according to the writings of the Roman historian Suetonius:

“We may still retreat: but if we pass this little bridge, nothing is left for us but to fight it out in arms.”

With the threat of exile and his political future on the line, Caesar decided to take his chances and cross the Rubicon into Rome on January 10.

According to Roman historian Plutarch, Caesar shouted “Alea iacta est” — “let the die be cast” — before crossing the stream and starting a five-year civil war that would ultimately end in the collapse of the Roman Republic and Caesar becoming Rome’s “dictator for life.”

Crossing The Rubicon In The Modern Age

Roman Bridge

A Roman bridge crossing over the modern-day Rubicon.

While it is difficult to pinpoint precisely when the idiom became commonplace, it is used frequently in modern popular culture.

Examples from the English Language Centers read:

“She crossed the Rubicon when she got that huge tattoo on her back!”

“Many European countries have crossed the Rubicon and taken the euro as their currency.”

Even in popular media, politicians and commentators often use this expression.

“David Cameron refuses to ‘cross Rubicon’ and write press law,” The Guardian wrote in 2012.

“The Rubicon Crossed: The Energy World Turned Upside Down After The Ukraine War,” Forbes wrote in a headline.

This idiom is not the only expression that stems from actual historical events. Many common sayings that we hear today also have their place in history.

For example, the idiom “white elephant” is rumored to have originated with a Siamese king who used the treasured animals as a punishment for unruly rivals.

According to legend, the king would present a white elephant to his rivals as a gift. The animals were notoriously difficult to care for and would often leave their owners in dire financial straits, given how difficult it was to sell them.

Today, “white elephant” means a burdensome or unwanted possession.

Other phrases include “turn a blind eye,” from the 1801 Battle of Copenhagen, to “crocodile tears,” from a 14th-century knight tale.

Even after thousands of years, these historical idioms and many others have stood the test of time — immortalized not just in the history of the world but also in our everyday conversations.


After reading about the idiom “crossing the Rubicon,” discover the assassination story of Julius Caesar in the Roman Senate. Then, read about the interesting origins of seven of English’s most common idioms.

author
Amber Breese
author
Amber Breese is an Editorial Fellow for All That's Interesting. She graduated from the University of Florida with a degree in political science, history, and Russian. Previously, she worked as a content creator for America House Kyiv, a Ukrainian organization focused on inspiring and engaging youth through cultural exchanges.
editor
Matt Crabtree
editor
Matt Crabtree is an assistant editor at All That's Interesting. A writer and editor based in Salt Lake City, Utah, Matt has a Bachelor's degree in journalism from Utah State University and a passion for idiosyncratic news and stories that offer unique perspectives on the world, film, politics, and more.