The Caesar vs Pompey Conflict: Rome’s Fight for Power and the End of the Republic
“If I fail, it will be said that I was ambitious; if I succeed, that I had courage.”
Julius Caesar
The Events Leading to the Caesar vs Pompey Civil War
As Caesar neared the end of his Gallic campaign, he sought a second consulship to maintain political immunity, fearing prosecution for controversial actions such as the massacre of the Usipetes and Tencteri in 55 BCE. Many senators, including Cato, opposed him, but in 52 BCE, ten tribunes passed a law allowing Caesar to move directly from his proconsular role to a potential consulship when his governorship ended in 50 BCE.
Despite this, Marcus Claudius Marcellus, consul in 51 BCE, argued Caesar's command should end after Vercingetorix's defeat, claiming the Gallic war was over. Surprisingly, Pompey opposed this and the issue was dropped. However, in 50 BCE, another Marcellus became consul and revived the debate. Tribune Gaius Scribonius Curio defended Caesar, proposing that if Caesar surrendered his command, Pompey should also give up his special command in Spain. Curio vetoed every motion against Caesar, and eventually, Pompey agreed to resign—only if Caesar did so first. A Senate vote favored simultaneous resignation, but Marcellus dissolved the session, ignoring the result.
In 49 BCE, yet another Marcellus became consul, and tensions escalated. Rumors falsely claimed Caesar had four legions in Cisalpine Gaul preparing for war; in truth, he had only one, stationed to deter barbarian raids. Acting unilaterally, Marcellus enlisted Pompey to defend the Republic. Pompey began raising troops, and new tribunes Mark Antony and Quintus Cassius Longinus took up Curio’s role of shielding Caesar.
When Metellus Scipio proposed declaring Caesar an enemy of the state if he didn’t relinquish command, Antony and Longinus vetoed the motion. In response, the Senate passed the Senatus Consultum Ultimum, overriding their veto. The tribunes fled to join Caesar. On January 11, 49 BCE, Caesar crossed the Rubicon with the 13th Legion, igniting civil war. Prominent figures like Titus Labienus and Marcus Brutus sided with Pompey.
The Battle of Dyrrachium (48 BC): Caesar’s Costly Defeat Against Pompey
By April, Mark Antony had arrived with the remainder of Caesar’s army—four legions and 800 cavalry. Their next objective was the strategic town of Dyrrachium, where Pompey had established an extensive 15-mile defensive line reinforced by 24 forts. Caesar managed to control the city's water supply by diverting streams, but his own forces were suffering from food shortages.
Once Caesar’s siege works were completed, Pompey was left with three options: break out, retreat by sea, or remain trapped. He chose to attack and launched several assaults on Caesar’s fortifications. During one of these, a Caesarean soldier named Marcus Cassius Scaeva distinguished himself by fighting heroically despite multiple wounds—including an arrow to the eye—earning a promotion to senior centurion and 200,000 sestertii.
After the failed assaults, Pompey adopted a defensive stance, refusing battle. This changed when two Gallic noble brothers, Roucillus and Egus, defected from Caesar and revealed weak points in the siege lines. Pompey exploited this intelligence and launched a devastating attack. In the ensuing battle, Caesar lost 960 men and 32 standards before withdrawing his forces from the area.
The Battle of Pharsalus (48 BC): Caesar’s Decisive Victory Over Pompey
Following Caesar’s defeat at Dyrrachium, many Greek towns hesitated to support him. To send a harsh message, he allowed his troops to sack the city of Gomphi, where civilians were killed and raped. Meanwhile, Pompey’s generals debated their next move—some urged an immediate attack on Caesar, while others preferred retaking the undefended Rome. Ultimately, Pompey chose to stay put, waiting for Caesar’s supplies to dwindle and for reinforcements under his father-in-law, Quintus Scipio, to arrive.
Once Scipio joined him, Pompey advanced and camped on a nearby hill, trying to lure Caesar into an uphill battle. When that failed, he launched a direct attack that ultimately cost him the war—despite having superior numbers. Labienus led a cavalry charge on the left flank, initially pushing Caesar’s forces back. However, Pompey’s cavalry was caught off guard by a concealed fourth line of Caesar’s infantry, which overwhelmed them. Caesar’s right flank then struck hard at Pompey’s left, causing his lines to collapse and his army to flee.
Caesar claimed 15,000 Pompeians were killed, though this number is likely exaggerated. Pompey fled to Egypt seeking refuge, but was murdered and beheaded on the orders of King Ptolemy XIII.