The Battle of Pharsalus was the decisive battle of Caesar's Civil War fought on 9 August 48 BC near Pharsalus, Central Greece.
 | Julius Caesar and his allies faced the command of Pompey. Pompey had the backing of a majority of Roman senators and his army significantly outnumbered the veteran Caesarian legions. According to Caesar, his own army included 22,000 Roman legionaries distributed throughout 80 cohorts (8 legions), with 1,000 Gallic and Germanic cavalry. Pompey was described as having 88 cohorts of Roman infantry, which at full strength would come to 44,000 men. |  Pompey also had 5,000 to 7,000 cavalry, and thousands of archers, slingers and light infantrymen in general. |
Pompey used his superior cavalry to try and crush Caesar's right flank. Caesar anticipated this and hid a select reserve of 3,000 close-quarters shock soldiers behind his lines. Caesar had studied Pompey's cavalry commander Titus Labienus. Labienus was a former top lieutenant of Julius Caesar who defected to Pompey at the start of the conflict.
 Gnaeus Pompeius Magnus (106-48 BC) ‘Pompey the Great’ | He commanded Pompey's large cavalry force. Caesar pulled 3,000 veterans from his third line and gave them an order that broke the rules of Roman warfare. Late Republican armies typically deployed in three lines. He ordered his 4th line men to hold their javelins like spears, and to not throw them.
 | They were ordered to advance and drive them into the rider's faces. When the legionaries unexpectedly advanced and drove steel toward their faces, the riders flinched, wheeled, and ran. Their retreat collapsed the entire Pompey flank. |
|  Titus Labienus |
The fourth-line legionaries couldn't outpace the fleeing cavalry, but they were soon among the lightly armed archers and slingers – men without armour, trained and equipped only to fight at a distance. They were cut down in large numbers. The fourth line then halted, reformed, and with the 3 line executed a devastating right hook, plunging into the exposed left flank and rear of Pompey’s main line. Pompey took horse and fled. Elements of his broken army rallied over the next day or two, but they surrendered when Caesar offered generous terms. The Caesarian army lost only 200 killed, including 30 centurions, while the Pompeians lost 15,000 killed and wounded, while more than 24,000 surrendered.