On August 9, 48 BC, during Caesar's Civil War, in the Battle of Pharsalus, Julius Caesar decisively defeated Pompey at Pharsalus, and Pompey fled to Egypt.
"Deployment
On the Pharsalian plain, Pompey deployed his infantry in the traditional three lines of 10 men deep, thusly: Legions I and III were on the left with Pompey himself; at his center were the legions from Syria commanded by Scipio, and on the right, against the Enipeus River, were legions from Cilicia and Spanish auxiliaries. Pompey's cavalry, which greatly outnumbered Caesar's, were commanded by Labienus, a brilliant cavalry commander and Caesar's old lieutenant during the Gallic Wars. They were massed in a single body on Pompey's left flank, together with his auxiliary archers and slingers. Pompey's tactical plan was to allow Caesar's legions to charge while his own stood their ground, reasoning that the enemy would fatigue by charging the double distance, and that his own men would better withstand the pilum toss while stationary. Simultaneously his cavalry would overwhelm the enemy's and then take the legions in the flank and rear — a classic hammer and anvil tactic.
Caesar also deployed his men in three lines, but, being outnumbered, had to thin his ranks to a depth of only six men, in order to match the frontage presented by Pompey. His left flank, resting on the Enipeus River, consisted of his battle worn IXth legion supplemented by the VIIIth legion, these commanded by Mark Antony. The center was commanded by Domitius and upon his right he placed his favored Xth legion, giving Sulla command of this flank — Caesar himself took his stand on the right, across from Pompey. Upon seeing the disposition of Pompey's army Caesar grew discomforted, and further thinned his third line in order to form a fourth line on his right: this to counter the onslaught of the enemy cavalry, which he knew his numerically inferior cavalry could not withstand. This new line he gave detailed instructions for the role they would play, hinting that upon them would rest the fortunes of the day, and gave strict orders to his third line not to charge until specifically ordered.
Progress of the battle
There was significant distance between the two armies, according to Caesar.[11] Pompey ordered his men not to charge, but to wait until Caesar's legions came into close quarters; Pompey's adviser Caius Triarius believed that Caesar's infantry would be fatigued and fall into disorder if they were forced to cover twice the expected distance of a battle march. Also stationary troops were expected to be able to defend better against pila throws.[12] Seeing that Pompey's army was not advancing, Caesar's infantry under Mark Antony and Gnaeus Domitius Calvinus started the advance. As Caesar's men neared throwing distance, without orders, they stopped to rest and regroup before continuing the charge;[13] Pompey's right and centre line held as the two armies collided.
As Pompey's infantry fought, Labienus ordered the Pompeian cavalry on his left flank to attack Caesar's cavalry; as expected they successfully pushed back Caesar's cavalry. Caesar then revealed his hidden fourth line of infantry and surprised Pompey's cavalry charge; Caesar's men were ordered to leap up and use their pila to thrust at Pompey's cavalry instead of throwing them. Pompey's cavalry panicked and suffered hundreds of casualties. After failing to reform, the rest of the cavalry retreated to the hills, leaving the left wing of Pompey's legions exposed. Caesar then ordered in his third line, containing his most battle-hardened veterans. These broke Pompey's left wing troops, who fled the battlefield.[14]
After routing Pompey's cavalry, Caesar threw in his last line of reserves[15] —a move which at this point meant that the battle was more or less decided.[citation needed] Pompey lost the will to fight as he watched both cavalry and legions under his command break formation and flee from battle, and he retreated to his camp, leaving the rest of his troops at the centre and right flank to their own devices. He ordered the garrisoned auxiliaries to defend the camp as he gathered his family, loaded up gold, and threw off his general's cloak to make a quick escape.[citation needed] As the rest of Pompey's army were left confused, Caesar urged his men to end the day by routing the rest of Pompey's troops and capturing the Pompeian camp. They complied with his wishes; after finishing off the remains of Pompey's men, they furiously attacked the camp walls. The Thracians and the other auxiliaries who were left in the Pompeian camp, in total seven cohorts, defended bravely, but were not able to fend off the assault.[16]
Caesar had won his greatest victory, claiming to have only lost about 200 soldiers and 30 centurions.[17] In his history of the war, Caesar would praise his own men's discipline and experience, and remembered each of his centurions by name. He also questioned Pompey's decision not to charge.[18]
Aftermath
Pompey fled from Pharsalus to Egypt, where he was assassinated on the order of Ptolemy XIII. Ptolemy XIII sent Pompey's head to Caesar in an effort to win his favor, but instead secured him as a furious enemy. Ptolemy, advised by his regent, the eunuch Pothinus, and his rhetoric tutor Theodotus of Chios, had failed to take into account that Caesar was granting amnesty to a great number of those of the senatorial faction in their defeat. Even men who had been bitter enemies were allowed not only to return to Rome but to assume their previous positions in Roman society.
Pompey's assassination had deprived Caesar of his ultimate public relations moment — pardoning his most ardent rival. The Battle of Pharsalus ended the wars of the First Triumvirate. The Roman Civil War, however, was not ended. Pompey's two sons, Gnaeus Pompeius and Sextus Pompey, and the Pompeian faction, led now by Metellus Scipio and Cato, survived and fought for their cause in the name of Pompey the Great. Caesar spent the next few years 'mopping up' remnants of the senatorial faction. After seemingly vanquishing all his enemies and bringing peace to Rome, he was assassinated in 44 BC by friends, in a conspiracy organized by Marcus Junius Brutus and Gaius Cassius Longinus."