Cicero travels with the Pompeian forces to Pharsalus in 48 BCE, though he is quickly losing faith in the competence and righteousness of the Pompeian lot.
He eventually provokes the hostility of his fellow senator Cato, who tells him that he would have been of more use to the cause of the optimates if he had stayed in Rome.
Both armies again make contact somewhere near what is today Fársala, Greece.
After several days of maneuvering, Pompey finally offers Caesar battle (August 9 by the uncorrected Roman calendar; June 6, Julian).
Caesar has approximately twenty-two thousand men, mostly hardened veterans; Pompey possibly has as many as forty-five thousand.
Pompey masses the main force of his cavalry on his left infantry wing, hoping to outflank and overpower Caesar's right wing, which is composed of a mixed band of cavalry and infantry.
Caesar, however, foresees the defeat of his right wing and has stationed behind it about two thousand of his best legionnaires.
In the ensuing battle, Pompey's cavalry drive back Caesar's cavalry, only to find itself faced by the advancing corps of select men using their pila as stabbing spears rather than as javelins.
Confused by the unusual infantry attack, Pompey's cavalry turns and flees.
The victorious legionnaires then begin to outflank the left wing of Pompey's infantry; at the same time, Caesar's third division, which has been held in reserve, is ordered to attack.
Pompey's legions break, and as the enemy storms the camp he himself flees to Larissa and the coast.
About twenty-four thousand of Pompey's troops surrender; the rest are dead or in flight.
When Caesar, whose casualties are less than two hundred and fifty, surveys the stricken field and Pompey's dead supporters he exclaims, “They would have it so” (“Hoc voluerunt”).
Pompey, hurried on by Caesar's rapid pursuit, loses contact with his own fleet; he sails first to Mytilene, where he meets his wife Cornelia and his son Sextus Pompeius.
He now wonders where to go next.
The decision of running to one of the eastern kingdoms is overruled in favor of Egypt.
