The Battle of Pharsalus

The Rubicon River marked the boundary between Rome and its provinces. No army was permitted to cross it. To do so was, in itself, an act of rebellion. And there stood Caesar, before the river. He gazed at the Rubicon for a long while. Behind him, countless soldiers waited for his command. There was but one thing they awaited: Caesar’s order to cross. At last, Caesar spoke: “The die is cast.” Thus began the Roman Civil War.

 

 

1. Background
When Caesar crossed the Rubicon, Pompey’s faction was thrown into confusion. They hadn’t expected Caesar to cross the Rubicon so quickly. Unprepared for war, Pompey’s faction abandoned the capital, Rome, and fled to Greece, where they began assembling a large army. Due to Caesar’s inferior naval power, he couldn’t immediately pursue Pompey. Instead, he entered Rome, gained the consulship, and then campaigned in Hispania, securing that region and thereby breaking part of Pompey’s encirclement of Caesar.

 

2. To Greece
Meanwhile, Marcus Calpurnius Bibulus, who was commanding Pompey’s fleet, died of a fever. This weakened Pompey’s naval defenses, and Caesar took the opportunity to cross the Adriatic Sea. Although he landed in Greece, Caesar could not expect supplies from Rome, as Pompey still controlled the naval dominance in the Mediterranean, including the Adriatic. In this context, the Battle of Dyrrhachium occurred, where Pompey emerged victorious. Afterward, Caesar moved into Thessaly, and Pompey pursued him. Eventually, the two armies met on the plains of Pharsalus, where the fate of the Roman Republic would be decided.

 

3. Army Sizes and Deployment
Caesar’s army consisted of around 22,000 legionaries and 1,000 cavalry, while Pompey’s army had around 36,000 legionaries and 7,000 cavalry. Many expected Pompey to win, as his army was nearly twice the size of Caesar’s, and especially because his cavalry force was seven times larger. However, Caesar’s army was made up of elite soldiers who had been hardened by eight years of warfare in Gaul. In contrast, Pompey had not commanded an army in battle for a long time, and his soldiers lacked experience. In other words, Pompey’s army had numerical superiority, while Caesar’s had superior quality. The 7,000 cavalry of Pompey’s army were concentrated on the extreme left wing, while the infantry was divided into three sections: left wing, center, and right wing. Caesar’s army was similarly deployed, but Caesar placed a contingent of 2,000 veteran soldiers along with cavalry on his extreme right wing.

 

4. Battle Progress
On August 9, 48 BC, Caesar’s heavy infantry charged first toward Pompey’s forces. However, Pompey did not respond, thinking that Caesar’s army would be easily defeated as they would be tired from running. Upon seeing Pompey’s forces remain still, Caesar’s heavy infantry briefly halted to reform their ranks before charging again. Pompey’s prediction was off; Caesar’s heavy infantry, considered the strongest in the Mediterranean at the time, were successfully holding off Pompey’s infantry. At this point, Pompey gave the order for his cavalry to charge. This was his hammer. While his infantry held the line, the cavalry was meant to strike Caesar’s flanks and rear, ensuring Pompey’s victory. As Pompey’s cavalry moved, Caesar responded by deploying his own cavalry. However, Caesar’s cavalry was supported by slingers who provoked Pompey’s cavalry with stones. Lacking experience, Pompey’s cavalry became distracted and pursued the slingers. Just as they were about to catch up with Caesar’s cavalry, a 2,000-man detachment from Caesar’s army ambushed Pompey’s cavalry from the side. Pompey’s cavalry was thrown into disarray and fled the battlefield. At this point, the core of Pompey’s forces was neutralized. The retreat of Pompey’s cavalry meant that Caesar’s flanks and rear were now secure. Caesar, positioned on the right wing, then attacked the exposed flank of Pompey’s left wing, while his cavalry struck Pompey’s rear. Pompey’s army collapsed rapidly, and Caesar’s forces pressed the attack, reaching Pompey’s camp. Pompey, the commander, was the first to abandon the battlefield and flee.

 

5. Battle Outcome
The casualties for Pompey’s army were about 6,000 killed and 24,000 captured. On the other hand, Caesar’s army suffered only around 200 casualties. It was a decisive victory for Caesar. When Pompey’s cavalry collapsed, Pompey himself fled the field. At the moment of the cavalry’s collapse, Pompey must have already sensed his defeat. It’s likely that he intended to gather new forces in the East and fight Caesar again. However, when news of his defeat spread, the provinces and cities under his influence, as well as his allies, refused to support him. Fleeing, Pompey arrived in Egypt, where he was eventually assassinated. This marked the tragic end of Pompey Magnus, the man once called “The Great.”