Jan. 10, 2022

Julius Caesar Crosses the Rubicon

Julius Caesar Crosses the Rubicon

January 10, 49 BC. A provincial governor named Julius Caesar marches his army across the Rubicon river, invading Italy and plunging the Roman Republic into Civil War.

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Cold Open

It's March 17th, 45 BC.

In the Roman province of Hispania, what is now southern Spain, two armies are locked in a fierce battle.

On one side are 70,000 Roman soldiers loyal to the late General Pompey. These men want Rome to remain a Republic, a representative democracy, with power resting in an elected Senate.

On the opposing side is the army of a maverick general named Julius Caesar, a man many consider a threat to the Republic. Four years ago, Caesar launched an attempt to bypass the democratic process and establish himself as dictator of the Roman Empire.

Pompey stepped forward as the defender of the Republic, the man who would protect Roman democracy from the power-hungry Caesar. But a year after his armies marched on Rome, Caesar defeated Pompey on the field of battle.

With his great rival dead, Caesar considered the Civil War won – and the path to uncontested power clear. But more resistance soon emerged in the shape of Pompey’s two sons. Intent on avenging their father’s death, they assembled an army in Hispania to overthrow Caesar.

Determined not to be outmaneuvered, Caesar sailed west with his legionnaires, sweeping across Hispania and pushing the republican forces back, until, eventually, the two sides met here outside the town of Munda.

Now, amid the clashing of swords and the constant rain of deadly arrows, Julius Caesar is struck by a rare moment of self-doubt. If he loses this battle, every victory so far will count for nothing. The future of the Roman Empire is at stake, and Caesar can feel it slipping through his fingers.

His army is outnumbered by 30,000 men. Positioned at the foot of a hill, Caesar and his soldiers are in a strategically weaker position. They have no choice but to grit their teeth and fight for their lives.

The Battle of Munda will be the final conflict in Julius Caesar's campaign to become the undisputed ruler of the Roman Empire. But Caesar's fate – and the fate of Rome – was decided long before these two armies collided. That moment came four years earlier, on January 10th, 49 BC, when Julius Caesar breached Roman law by marching his army across the Rubicon River, setting in motion a series of events that would change the course of Western civilization.


From Noiser and Airship, I’m Lindsay Graham and this is History Daily.

History is made every day. On this podcast—every day—we tell the true stories of the people and events that shaped our world.

Today is January 10th: Julius Caesar Crosses the Rubicon.

Act One: The Die is Cast

It's April, 59 BC, fourteen years before the Battle of Munda.

In Rome, a wedding is underway. The bride and groom stand before an altar of Jupiter and a priest makes an offering. Once their union has been sealed, the guests rush forward to congratulate the newlyweds.

Standing slightly apart from the crowd is forty-year-old Julius Caesar. Dressed in a crimson toga, the renowned general looks on as the attendees shower the bride and groom with gifts. His stern expression is hard to read, but in Caesar's steel-gray eyes, there gleams an unmistakable look of triumph.

Across the marble atrium, the groom glances up from the smiling crowd of well-wishers and catches Caesar's eye. It's a fleeting moment, unnoticed by the other guests, but the look the two men exchange seems to contain a greater weight of significance than any of the wedding vows.

The groom is the Roman general and statesman, Gnaeus Pompeius Magnus, better known as Pompey. His military exploits have expanded Rome’s Empire and helped Pompey establish himself as an influential senator.

By contrast, Caesar is a more divisive figure. Following military conquests in Spain, Caesar returned to Rome where he wishes to run for consul – the highest political office in the land.

But powerful enemies stand in his way. Many senators suspect Caesar is being overly ambitious, and regard his populist agenda as a potential danger to the political establishment.

So Caesar decided to form an alliance. By marrying off his daughter, Julia, to the influential Pompey, he has secured a key ally in the Senate. And Pompey, the shrewd tactician, recognizes Caesar's popularity among the common people. Both men will benefit from this arranged marriage.

But there's another man that stands out within the crowd of wedding guests: an older politician named Marcus Licinius Crassus. Caesar brought Crassus, the richest man in Rome, into his confidence for obvious reasons. With Crassus’ financial backing, Caesar’s election to consul is all but guaranteed.

Caesar, Pompey, and Crassus form what will become known as the First Triumvirate. Their alliance pays off. Caesar is elected consul in 59 BC. And from this position, he passes reforms through the Senate that directly benefit his allies, Pompey and Crassus.

The Triumvirate’s growing strength highlights cracks emerging in the foundations of Roman democracy. For centuries, the Republic has operated as a system of checks and balances preventing individuals from gaining excessive power. But as Rome’s Empire continues to expand, the men leading its expansion acquire greater territory and wealth overseas, and the system designed to contain their power begins to look increasingly fragile.

When Caesar's consulship ends in 58 BC, he assumes the governorship of Cisalpine Gaul, an area just south of the French Alps. Caesar leaves Rome with four legions and travels north to take up his new post. The aristocratic establishment in the Senate, men who resent the rise of powerful generals like Caesar, are relieved to see him go. They hope his departure will mark the beginning of the end for Julius Caesar.

But Caesar has no intention of quietly fading into the background. With his legions in tow, he marches north into modern-day France and begins subjugating its inhabitants, the Gauls. What follows is a series of bloody conflicts, known as the Gallic Wars.

By 52 BC, over one million Gauls have been slaughtered, Caesar has extended Rome's Empire as far north as Britain, and he has accumulated even more wealth and prestige.

Back in Rome, a sense of foreboding darkens the mood in the Senate. The aristocrats there – a group known as the Optimates – fear that once Caesar has conquered Gaul, he will return to Rome with his army and seize power.

By now, the Triumvirate with Crassus and Pompey has collapsed. Crassus died in combat in 54 BC. Later that same year Julia, Pompey's wife, and Caesar's daughter, also passed away. So with the family bond shattered, so too is Pompey and Caesar’s alliance. With Caesar away in Gaul, Pompey realigns himself with the Optimates and joins their efforts to curtail Caesar's growing power.

They present Caesar with an ultimatum: step down as governor of Gaul and disband his army or be removed by force. But Caesar stands his ground. He wishes to remain governor for one more year, before running again for consul. 

Rather than bending to Caesar’s wishes, the Optimates rally around Pompey, entrusting the defense of the Roman Republic to him. Caesar decides to mobilize his troops. In January 49 BC, he begins marching his army through Gaul toward Italy. It’s a power play, a show of strength aimed at convincing the Senate to accept his terms.

But the Senate does not acquiesce. No diplomatic solution can be found. And by January 10th, Caesar and his army reach the Rubicon River, which separates Italy from Gaul. Here, Caesar orders his men to halt.

By crossing the Rubicon, Caesar will be invading Italy and declaring war on the Republic. But if he backs down, he will be hounded by the Senate and stripped of political office. The gravity of the decision weighs heavy on Caesar’s shoulders, and as the moon rises over the Rubicon, there’s still no knowing which course of action he will ultimately take.

Act Two: Civil War

It's January 10th, 49 BC.

It's a cold, clear night on the bank to the Rubicon. Julius Caesar stares out into the silvery moonlight and watches as it glimmers on the surface of the narrow river. Behind him, 4000 soldiers anxiously await orders, their breath rising from their helmets in clouds of freezing mist. 

Caesar understands the severity of the act he is considering. If he crosses this river, the future of Rome will not be decided on the senate floor, but on the battlefield.

It's not clear what ultimately tips Caesar's deliberations in favor of war. Some claim he was visited by a supernatural apparition who urged him to cross the river. Others claim Caesar was simply consumed with ambition. Whatever the case, at some point before midnight, Caesar marches his army across the Rubicon, turning to an aide as he does so and uttering the now-famous phrase: "the die is cast." 

Caesar and his army capture every city they pass on their way to Rome. When news reaches Pompey of the invasion, he declares a state of civil war, and orders all senators to follow him in evacuating the city. Pompey has not yet been able to muster a force to match Caesar’s, so he retreats to Greece to assemble an army there.

Before long, Caesar has taken Rome itself. Leaving one of his generals in command of the city, Caesar sets out for the western province of Spain. There, he lays siege to towns and cities and by the end of the year, Spain too has been conquered.

With Spain and Italy now under Caesar's control, the rogue general sets his sights on Greece and Pompey. Caesar's fleet sails across the Adriatic Sea, where they engage in naval skirmishes with Pompey's ships.

Eventually, Caesar is able to land his army on the coast of Greece. There they march inland. The decisive battle comes in August of 48 BC. On a blazingly hot day, the two sides clash on the dusty plain of Pharsalus in central Greece.

The odds are stacked against Caesar. Pompey's 36,000 legionnaires far outnumber Caesar's force of 22,000. But Caesar has a key advantage: his soldiers are hardened by years of combat. Gaul, Spain, and Italy have all fallen beneath the blade of Caesar’s legions. His men possess something that manpower alone cannot provide: confidence. 

During the battle, Pompey attempts a flanking maneuver, but it fails, exposing his army to a counter-offensive. Caesar capitalizes on the opportunity, and his men quickly overpower Pompey’s infantry. By nightfall, the battle is over. And once again, Caesar has emerged victorious.


A defeated Pompey flees with his remaining ships to Egypt. Weeks later, Pompey lands at the Port of Pelusium on the banks of the Nile River. There, he hopes to throw himself on the mercy of King Ptolemy of Egypt.

But Ptolemy can see which way the wind is blowing. Wishing to remain in Caesar’s favor, Ptolemy sends officers to Pompey's ship. They climb aboard and, in front of the general's weeping wife and child, murder Pompey.

When Caesar lands in Egypt three days later, Ptolemy sends him Pompey’s head as a gesture of respect. But the sight does not please Caesar, who weeps for his great rival and former ally.

In the end, Caesar will not leave Egypt until the middle of 47 BC. During that time, he becomes embroiled in a struggle between King Ptolemy and Ptolemy's sister, Cleopatra, who believes herself to be the rightful queen of Egypt.

But it's not politics that keeps Caesar in Egypt, it's love. He and the beautiful Cleopatra begin a romantic relationship, in which Caesar helps her depose her brother and establish herself as Egypt's ruler. 

But while Caesar is plotting lounging in the royal courts of Egypt, Pompey's army is steadily regrouping, now under the command of Caesar's long-standing enemies: the senator Cato and the general Scipio. Both of these men were part of the original group of Optimates who opposed Caesar.

In 46 BC, Caesar's legions meet Cato and Scipio's massive army at Thapsus, in modern-day Tunisia. But despite facing an army comprising 12 legions, 15,000 cavalrymen, and 60 mounted war elephants, Caesar again is the victor. 

Scipio and Cato take their own lives in the wake of their defeat. Other Optimates, like Cicero, surrender to Caesar and pledge their support. 

By 45 BC, Caesar is back in Rome. With the entirety of the Empire now under his command, and with all his greatest rivals vanquished, Caesar is declared dictator – a position in Ancient Rome, reserved for times of crisis, which invests its holder with supreme authority.

But soon, word reaches Caesar that Pompey's sons have mounted a rebellion in Spain. So the newly appointed dictator assembles a fleet and sails west. After the death of Pompey, and the defeat of Cato and Scipio, Caesar thought the last of his enemies were dead. He has discovered that he was mistaken. But as he stands at the prow of his westbound ship, Caesar is determined that by the time he returns from Spain, all his enemies, every one of them will be vanquished.

Act Three: Dictator for Life

It's March 17th, 45 BC. The Battle of Munda is underway in southern Spain.

Julius Caesar and his legions are heavily outnumbered, but after hours of stalemate, a tactical error gives Caesar the upper hand. By reinforcing their left flank, the Pompeian forces severely weaken their right flank. Caesar spots this, sends more legions to attack the right, and they soon overwhelm the enemy.

Victorious yet again, Caesar will soon return to Rome, now secure in the knowledge that the last of his opponents are destroyed. He will be named Rome's first "dictator for life", and will begin introducing a series of reforms designed to entrench his authority.

But he will not succeed. On March 15th, 44 BC, a group of senators who have grown wary – or perhaps jealous – of his power will find Caesar in a small moment of weakness and assassinate him.

The Roman Republic had stood as one of the world’s earliest prominent and vital democracies. But with Caesar's appointment as dictator, the Roman Republic was replaced with the Roman Empire, a system of hereditary rulers and not elected officials, one that would grow increasingly autocratic and corrupt. And it all started with the fateful decision to cross the Rubicon on January 10th, 49 BC.


Next on History Daily. January 11, 1794. In the American state of Georgia, a man named Robert Forsyth becomes the first United States Marshal killed in the line of duty.

From Noiser and Airship, this is History Daily, hosted, edited, and executive produced by me, Lindsay Graham.

Audio editing by Mollie Baack.

Music and sound design by Lindsay Graham.

This episode is written and researched by Joe Viner.

Executive Producers are Steven Walters for Airship, and Pascal Hughes for Noiser.