Caesar Crosses the Rubicon (49 BC): The Die Is Cast

Caesar’s crossing of the Rubicon in January 49 BC was the moment when Julius Caesar led armed troops out of his province and into Italy, defying the Roman Senate and starting a civil war against Pompey the Great. The small river in northern Italy marked a legal boundary that no governor could cross with an army. By doing so, Caesar set off the chain of events that ended the Roman Republic, and the phrase “crossing the Rubicon” has meant an irreversible decision ever since.

Background: a republic under strain

By the 50s BC the Roman Republic was dominated by powerful generals rather than by the Senate and the annual magistrates. In 60 or 59 BC Caesar, Pompey and the wealthy Marcus Licinius Crassus formed an informal political alliance known as the First Triumvirate. It gave Caesar the consulship of 59 BC and then a long command in Gaul.

Over the following decade Caesar conquered the whole of Gaul in the Gallic Wars. He gained enormous wealth, a loyal veteran army and great popularity in Rome. His success also alarmed conservative senators, known as the Optimates, led by figures such as Cato the Younger, who saw him as a threat to the Republic.

The alliance between the three men came apart. Pompey’s wife Julia, Caesar’s daughter, died in 54 BC, removing a personal link between them. Crassus was killed fighting the Parthians at the Battle of Carrhae in 53 BC. Pompey drew closer to the Optimates and in 52 BC was made sole consul to restore order after riots in Rome.

The dispute over Caesar’s command

The immediate cause of the crisis was the end of Caesar’s command in Gaul. As a serving governor, Caesar was immune from prosecution. His enemies made clear that once he returned to private life they would put him on trial for illegal acts committed during his consulship of 59 BC.

Caesar’s solution was to move directly from his governorship into a second consulship. A law passed in 52 BC with Pompey’s support allowed him to stand for the consulship without coming to Rome in person. His opponents worked to cancel this privilege and to replace him in Gaul before he could be elected, so that there would be a gap in which he could be prosecuted.

During 50 BC the tribune Gaius Scribonius Curio, who had gone over to Caesar’s side, proposed that both Caesar and Pompey should give up their armies at the same time. According to Plutarch and Appian, the Senate voted for this by a huge majority, 370 to 22, but the consul Gaius Claudius Marcellus refused to accept the result. Marcellus instead asked Pompey to take command of the forces in Italy and defend the state.

On 1 January 49 BC a letter from Caesar was read to the Senate. In it he offered to lay down his command if Pompey did the same, but he warned that he would defend his position and that of the Roman people if he were wronged. The Senate, dominated by his opponents, rejected the offer and ordered him to give up his army by a set date or be treated as a public enemy.

Two tribunes friendly to Caesar, Mark Antony and Quintus Cassius Longinus, vetoed the decisions. On 7 January the Senate passed its emergency decree, the senatus consultum ultimum, instructing the magistrates to see that the state came to no harm. The tribunes, warned that their safety could not be guaranteed, fled from Rome disguised as slaves and made their way north to Caesar.

Caesar was waiting at Ravenna, the last major town of his province, with a single legion, the Thirteenth. When news of the decree and the flight of the tribunes reached him, he had a clear grievance to present to his soldiers: the sacred rights of the tribunes of the people had been violated.

Crossing the Rubicon

The Rubicon was a small river flowing into the Adriatic between Ravenna and Ariminum, modern Rimini. It formed the boundary between the province of Cisalpine Gaul and Italy proper. Roman law forbade a governor to lead his troops beyond his province without the authority of the Senate and people, so crossing it under arms meant open rebellion.

The most detailed accounts come from writers of the following century and a half, Suetonius and Plutarch, who drew on earlier sources including the historian Gaius Asinius Pollio, who was with Caesar. According to Suetonius, Caesar spent the day at Ravenna acting normally, watching public shows and attending a banquet, so as not to reveal his plans. At nightfall he left secretly in a carriage drawn by mules, lost his way in the dark and found guides only towards dawn, before rejoining his troops at the river.

Both Suetonius and Plutarch describe Caesar hesitating at the bank and discussing with his companions the terrible consequences of crossing and of not crossing. Suetonius adds a story of a mysterious figure of great size and beauty who appeared playing a reed pipe, seized a trumpet from a soldier, sounded it and crossed the river, which Caesar took as a sign from the gods.

The crossing is traditionally dated to about 10 January 49 BC by the Roman calendar then in use. That calendar had drifted badly out of line with the seasons, and in solar terms the event probably took place in late autumn of 50 BC. Caesar’s troops then occupied Ariminum without resistance.

“The die is cast”

The words most closely associated with the crossing come from Suetonius, who reports Caesar as saying in Latin “Alea iacta est”, “the die is cast”. Plutarch gives a slightly different version: he says Caesar spoke in Greek, quoting a line from the comic playwright Menander that is better translated “let the die be cast”. The Greek version suggests a gambler’s resolve rather than a statement of fact.

Ancient writers disagreed on details, and no contemporary record preserves the exact words. Even so, the saying is attested by two independent ancient authors and has been linked with Caesar ever since. It is now used in many languages to describe any decision from which there is no turning back.

Myths and facts

A common assumption is that Caesar himself made much of the Rubicon. In fact, his own account of the war, the Civil War, does not mention the river at all. He describes addressing the Thirteenth Legion at Ravenna about the wrongs done to him and to the tribunes, and then simply says that he set out for Ariminum. Caesar had good reason to play down the moment when he broke the law.

Another misconception is that Caesar crossed with his whole army. He took only one legion, perhaps 5,000 men, with some cavalry, and ordered the rest of his forces in Gaul to follow. His speed and boldness, rather than numbers, explain his early success.

It is also often said that the modern river called the Rubicone is certainly the ancient Rubicon. The river courses in the area have changed over two thousand years, and several streams have been proposed. In 1933 the Italian government officially identified the Rubicon with the Fiumicino, renamed Rubicone, and the town of Savignano added “sul Rubicone” to its name, but scholars still regard the identification as uncertain.

Key people

• Gaius Julius Caesar (100–44 BC): conqueror of Gaul, former consul and governor of Cisalpine and Transalpine Gaul and Illyricum, who chose war rather than surrender his command.
• Gnaeus Pompeius Magnus, Pompey the Great (106–48 BC): Rome’s most celebrated general before Caesar, who commanded the forces of the Senate.
• Mark Antony (83–30 BC): tribune of 49 BC, whose flight from Rome gave Caesar a political justification for war.
• Cato the Younger (95–46 BC): leading Optimate senator and Caesar’s most determined opponent.
• Gaius Scribonius Curio (died 49 BC): tribune of 50 BC and Caesar’s agent in Rome, later killed fighting for him in Africa.

What happened next

Caesar moved with great speed. Town after town in northern and central Italy opened its gates to him. Pompey, whose forces in Italy were not ready for war, decided to abandon Rome, and many senators and both consuls left the city with him, leaving the treasury behind in their haste.

At Corfinium in February 49 BC, Caesar besieged the Optimate commander Lucius Domitius Ahenobarbus, whose troops surrendered. Caesar released Domitius and the other senators unharmed. This policy of clemency, mercy towards defeated Roman opponents, became a deliberate feature of his campaign and contrasted with the bloody purges of Sulla a generation earlier.

Pompey retreated to Brundisium (Brindisi) and on 17 March 49 BC sailed for Greece with his army, planning to gather the resources of the eastern provinces. Caesar, without a fleet to follow, turned first to Spain, where he defeated Pompey’s generals Afranius and Petreius near Ilerda in the summer of 49 BC.

Caesar then crossed to Greece and, after a setback at Dyrrachium, defeated Pompey decisively at the Battle of Pharsalus in August 48 BC. Further campaigns in Egypt, Asia Minor, North Africa and Spain followed before the war ended at Munda in 45 BC.

Timeline

• 52 BC: A law allows Caesar to stand for the consulship without returning to Rome.
• 50 BC, December: The Senate votes 370 to 22 for both Caesar and Pompey to disarm, but the consul Marcellus ignores the vote.
• 49 BC, 1 January: Caesar’s letter offering to disarm with Pompey is read and rejected in the Senate.
• 49 BC, 7 January: The Senate passes its emergency decree; the tribunes Antony and Cassius flee to Caesar.
• 49 BC, c. 10 January: Caesar crosses the Rubicon with the Thirteenth Legion and takes Ariminum.
• 49 BC, February: Caesar captures Corfinium and pardons the defeated commanders.
• 49 BC, 17 March: Pompey sails from Brundisium to Greece.
• 48 BC, 9 August: Caesar defeats Pompey at Pharsalus.

Legacy

The crossing of the Rubicon is one of the most famous turning points in ancient history. It marked the moment when a dispute among Rome’s elite became a war between Roman armies, and it led to Caesar’s dictatorship, his assassination in 44 BC and, after further civil wars, the rule of Augustus as the first emperor.

The event also reshaped the language of politics. “To cross the Rubicon” now means to take a step that commits a person or a country to a course of action, and “the die is cast” signals the same point of no return. Painters, playwrights and historians from the Renaissance onwards have returned to the scene of Caesar at the riverbank as an image of personal ambition and decisive choice.

Historians still debate Caesar’s motives. Some stress his fear of prosecution and loss of status, others the stubbornness of his opponents who refused every compromise. Most agree that both sides bear responsibility for a war that neither fully wanted but neither was willing to avoid.

Why it matters

The crossing of the Rubicon turned a constitutional quarrel into civil war and set the Roman Republic on the path to one-man rule. It remains the classic example of an irreversible decision, remembered in everyday language more than two thousand years later.