The Battle of Pharsalus, when Caesar drove out Pompey

Pompey fled Pharsalus to Egypt, where he was assassinated on the orders of Pharaoh Ptolemy XIII. Curiously, Ptolemy XIII sent Pompey’s head to Caesar in an effort to win his favour, but instead secured an angry enemy. Ptolemy, advised by his regent, the eunuch POTINUS, and his rhetorical tutor Theodotus of Chios, disregarded the fact that Caesar granted amnesty to a large number of his enemies after his defeat. Even men who had been his bitter enemies were allowed not only to return to Rome, but to assume their former positions in Roman society.


The Battle of Pharsalus was a decisive engagement in the Second Civil War. On 9 August 48 BC at Pharsalus in central Greece, Gaius Julius Caesar and his allies faced the Republican army under the command of Gnaeus Pompey Magnus. Pompey had the backing of a majority of senators, many of whom were Optimates, but his army was inferior to Caesar’s veteran legions. The battle is often considered decisive for the end of the Republic and the beginning of the Roman Empire.

Pharsalus ended the war between the First Triumvirate but not the inter-Roman civil war, ending Caesar’s hopes of a quick victory. Two of Pompey’s sons, Cnaeus and Sextus, and the Pompeian faction, now led by Metellus Scipio and Cato, survived and fought for their cause in the name of Pompey the Great. Caesar spent the next few years wiping out the remnants of the senatorial faction, but as Cicero reflected after Tapso, military superiority had been irrevocably won by Caesar at Pharsalus. Moreover, the senatorial command (including Pompey) had discredited itself by abandoning the army to its fate.

After destroying all his enemies and bringing peace to Rome, he was assassinated by his friends in a conspiracy organised by Marcus Junius Brutus and Gaius Cassius Longinus.37

Related to the battle was Caesar’s plan to launch a punitive campaign against Berberists for their support of Pompey, in 44 BC he had assembled 16 legions and 10,000 horsemen with the aim of attacking Dacia but the campaign was not carried out because of his assassination.

The Road to Battle

A dispute between Caesar and the Senate of Rome culminated in the march of his army towards Rome, forcing Pompey and much of the Roman Senate to flee Italy for Greece in 49 BC, where he could best recruit an army to take on his former ally. Caesar, lacking a fleet, consolidated his control over the western Mediterranean – Hispania specifically – before getting ships to pursue Pompey. Pompey had appointed Bibulus to guard his fleet of 600 ships and to set up a massive blockade, with orders to prevent Caesar from crossing into Greece and to prevent him from receiving aid from Italy. Caesar defied convention and came up with a plan to cross the Adriatic during the winter with only half the ships needed. This move surprised Bibulus and the first wave of managed ships was able to break the blockade with ease. Although Bibulus managed to prevent the other ships from crossing the Adriatic, he died shortly afterwards, presumably from exhaustion.

Caesar was in an extreme position, with a beachhead in Epirus, with only half his army, some 25,000-30,000 men, no ability to supply his troops by sea, and limited local support because the Greek cities were mostly loyal to Pompey. Caesar’s only option was to fortify his position, get as many supplies as possible and wait for the rest of his army to attempt another crossing.

Pompey already had a large and varied army, some 100,000 men between recruits and allies, yet his troops were mostly raw recruits and Caesar’s soldiers were hardened veterans. Realising Caesar’s difficulty in keeping his troops supplied, Pompey decided to simply let starvation destroy his enemy without a fight. Caesar began to despair and used every channel he could think of to seek peace with Pompey. When this was rejected, he made an attempt to cross back into Italy to pick up the missing troops, but was turned back by a storm. Finally Mark Antony managed to break the blockade and reach Greece with 20,000 reinforcements. Then, with all his strength, Caesar felt ready to face Pompey.

Pompey camped in a strong position south of Dirraquium with the sea at his back and surrounded by hills to make a direct assault impossible. Caesar ordered a fence to be built around Pompey’s position in order to cut off his access to water and pasture for his horses. Pompey built a parallel wall and in the midst of a kind of no-man’s land, a fight had been created very similar to the trench warfare of the First World War. Finally, the engagement ended because a traitor to Caesar’s army informed Pompey of a weak point in Caesar’s fence. Pompey immediately seized on this information and forced Caesar’s army into a general attack, but ordered his army not to pursue for fear of Caesar’s reputation for setting elaborate traps. Pompey continued his strategy of exhausting Caesar’s forces and avoiding direct confrontation. After encircling Caesar in Thessaly, prominent senators in Pompey’s camp began to argue for a decisive victory. Although Pompey was strongly against it he finally relented and accepted Caesar’s battle in a field near Pharsalus. In fact, Enobarbus called him Agamemnon, “king of kings”, because he led characters who considered themselves kings.

In his Commentaries on the Civil War, Caesar credits Pompey with 110 cohorts (some made up of Hispanic soldiers brought by Aphranius and fighting as heavy infantry) although he garrisoned the camp with 22 during the battle, some 47,000 men under the command of Publius Cornelius Lentulus Spinther (right wing), Metellus Scipio (centre), Lucius Domitius Enobarbus (left wing) and Titus Labienus (cavalry). Only 2,000 were veterans.

Caesar himself had 80 cohorts, severely depleted by the many battles they had been involved in, but also very experienced, totalling 22,000 men, superbly led by Mark Antony (left wing), Cnaeus Domitius Calvinus (centre) and Publius Cornelius Sulla (right wing). Caesar’s army was composed of the following legions, the Gallic War veterans X, VIII, IX, XII and the newly created legions I, III and IV. On the day of the battle Caesar left 2,000 veterans in camp.

The disparity in cavalry would be even greater, with 6700 Pompeian horsemen against barely 1000 Caesarians, of whom about 600 would be Gauls – probably Aedui – and about 400 Germanic Ubians, in addition to Caesar’s personal escort of Hispanic horsemen.

For Delbrück, although the advantage of the Pompeians is true, the proportions given by Caesar, taking into account the course of the battle, are exaggerated, especially in terms of cavalry. A more realistic figure might be 40,000 Pompeian infantry – with some 5,000 auxiliary infantry recruited in Hispania and another 4,200 allies – against 30,000 Caesarians – including 7,000 allies – and 3,000 Pompeian horsemen against 2,000 Caesarians.

However, the Caesarian army had the advantage over the Pompeian army in that its legions were veteran troops, distinguished by the conquest of Gaul, the expeditions to Britain and Germania and the Ilerda campaign, accustomed to the harsh conditions of life and the ferocity of hand-to-hand combat. Pompey’s legionaries, on the other hand, were young men newly recruited by the Senate with little or no previous combat experience.

Another difference was command. Caesar’s legionaries were absolutely loyal to him and their commander possessed great charisma with which he could win the loyalty of his troops. Whereas Pompey did not possess a connection with his troops, because in addition to being newly recruited, the commander himself had been retired from the battlefield for more than a decade after discharging his old army, which also contrasts with the fact that Caesar’s reputation as a successful general was recent and this influenced his and his enemy’s legions.

Another factor in Caesar’s favour was the fact that the lack of supplies and the isolation to which Caesar’s troops were subjected left them with no choice but victory or death, unlike his adversary who had flight as a reasonable option for survival.

The confined space of the battlefield also favoured Caesar as it prevented Pompey from making better use of his numerical superiority. It is possible that the pressure exerted by the senators to finish Caesar off quickly prevented him from seeking a better scenario, weakening his enemy further or recruiting more men, as it is possible that he knew his own disadvantages due to his vast experience.

Brother against brother

The two armies supported one of their flanks on a stream and concentrated all their cavalry on the other. However, the commanders’ ideas about the conduct of the battle differed substantially, and this is where Caesar’s genius can be seen. For while Pompey would try to win with his numerical superiority, Caesar, foreseeing this move, planned an effective defence, defeating the enemy cavalry and counterattacking, in turn, from the flank.

To do this, Caesar decides to reinforce his cavalry with infantry, he has 6 of his most experienced cohorts forming an oblique line on the flank, just behind his main line, and he also keeps others in reserve. This weakens the centre of the army considerably, but Caesar is confident that his veterans can withstand his opponent’s thrust. The initial disposition of these cohorts was beyond Pompey’s vision, so their action would come as a surprise.

The battle begins with the two forces approaching each other slowly, as it is important for the plans of both sides that the battle in the centre does not begin quickly. The Pompeian cavalry rushes forward, as planned, but the Caesarian cavalry retreats in a feigned flight, the only purpose of which is to draw the enthusiastic enemy cavalry towards the well-equipped cohorts to fight them.

The flank cohorts then begin to manoeuvre, driving the Pompeian cavalry back and attacking the enemy flank. By this time, the legionaries on both sides have come into contact, and Caesar orders his reserve to reinforce the centre of the army. Attacked in two places, the Pompeian army begins to crumble on the flank. As the Caesarian cavalry pursues its rival off the battlefield. Seeing that the battle is lost, Pompey retreats to the camp. Caesar writes in his Commentaries that in the two hours of the battle he had 200 casualties among the legionaries and 30 among the centurions (not counting the casualties inflicted on his auxiliary troops and allied cavalry) and that his enemy had about 15,000. It is quite possible that Caesar’s total casualties were as high as 1200 men. It is easy to explain this discrepancy in the loss of men, considering that Pompey’s troops fought without order or order against Caesar’s solid cohorts formed in battle order. The surviving Pompeian army surrendered on the morning of the next day, some 23,000 to 24,000.

On the loss of his centurions, Caesar notes with great sorrow in his writings, among them his faithful Gaius Crastinus, a very high proportion that would indicate the high degree of responsibility that his commanding cadres reached, willing to sacrifice themselves to avoid the useless loss of legionaries.

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