Pharsalus, modern-day Farsala, is a city in central Greece, in southern Thessaly. It was the site of one of the most important Roman battles – the climactic clash between Julius Caesar and Pompey the Great, on August 9, 48 BC.
When Caesar crossed the Rubicon River with Legio XIII Gemina, a treasonous act in January of 49 BC, he knew he was declaring war against the Senate and the optimates. Although he was heading from Gaul to Rome with only one legion, it was enough to force Pompey and most of the Senate to flee to Greece. Caesar didn’t have the resources to chase them, so he worked to strengthen his forces and through Spain gained the fleet he needed. Pompey had the backing of most of the Senate and had a far more substantial number of troops to command. However, the army Caesar did have was comprised of veterans, as opposed to a lot of fresh recruits on the part of Pompey.
When Caesar pursued Pompey in 48 BC, he commanded only around 22,000 troops and was facing Pompey’s 40-45,000. Vastly outnumbered and pinned down by Pompey’s blockade of 600 ships, Caesar was forced to fortify the beachhead at Epirus and forage for food, as he had to cross the Adriatic Sea during winter with only half of his army. Pompey knew he had the upper hand and planned to just wait it out, since Caesar could not get help from Italy and most of the surrounding area was loyal to Pompey. Eventually starvation would cause Caesar to surrender. Meanwhile, Marc Antony was rallying the troops in Italy and made way with his ships to the blockade, breaking it and rejoining Caesar’s forces.
With his army as good as it was going to get, Caesar decided to take the battle to Pompey. He built a wall around Pompey’s forces to cut them off from fresh water and pasture land, with Pompey responding by building a parallel wall. This caused a standoff until a traitor from Caesar’s camp went to Pompey’s camp with information about a weakness in the wall. Pompey pounced on the opportunity, forcing Caesar to retreat, but Pompey didn’t pursue, fearing a trap. Caesar continued to retreat and retrench and Pompey mirrored his actions. It wasn’t until Caesar was in Thessaly that the senators in Pompey’s camp had had enough. They wanted a decisive victory and forced Pompey to abandon his winning strategy of wearing down Caesar.
The Romans were extremely disciplined and routine in their battles. As such, both Caesar and Pompey pretty much knew what the other would do with the resources they had. Since Caesar was the aggressor, Pompey ordered his troops to wait for Caesar to charge. There was a bit of distance between the camps, so Pompey’s advisor calculated the infantry would be tired from marching by the time of engagement. And since Caesar had less than half the number of troops of Pompey, the lines were only half as deep. But, Caesar had a plan and needed to do something to overcome the odds stacked against him. Instead of three lines, as was usually used, on one of his flanks he shuffled some troops around from the third line and made a fourth line. He ordered them to wait until signaled and the third line was not to charge until ordered.
Caesar’s infantry started the advance under Marc Antony and Gnaeus Domitius Calvinus, along with the left and center wings. These forces clashed with Pompey’s center and right wings, leaving Caesar and his right flank facing off against Pompey and his left flank. As expected, Pompey’s cavalry was able to push back Caesar’s cavalry. However, what Pompey didn’t expect was the hidden fourth line. The infantry is supposed to throw their pila (javelins) at the enemy when in range, but Caesar instead instructed them to thrust them like spears at the cavalry. Pompey’s cavalry was surprised and confused by this line and method of attack and broke ranks, allowing Caesar’s infantry to inflict serious casualties, along with exposing the left flank of Pompey’s legions. Caesar ordered his third line, which consisted of his best battle-worn veterans from Legions VIII, IX, X and XII to attack the exposed flank, causing that wing to flee.
Pompey, witnessing his cavalry scattered and his legions breaking lines, personally retreated back to camp and left the troops to fend for themselves. Pompey ordered the Thracians and auxiliaries in camp to defend it while he fled with his family and all the gold he could take. By the end of the day, according to Caesar’s count, he had lost around 230 troops while wiping out between 6-15,000 of Pompey’s forces and taking over the Pompeian camp. It was Caesar’s greatest victory.
Pompey fled to Egypt, where he was greeted by an agent of Ptolemy XIII, and beheaded.