What happened
Pompey held the stronger position and the larger army and had been avoiding a decisive engagement, a strategy that was working and that his senatorial allies would not tolerate.
Pompey's plan was to use his cavalry superiority to sweep Caesar's small cavalry from the field and envelop the Caesarian right.
Caesar, anticipating this, withdrew cohorts from the third line of his legions and formed a concealed fourth line at an angle behind his right, instructing them to use their javelins as thrusting weapons against the faces of the cavalry rather than throwing them.
The Pompeian cavalry charged, drove off Caesar's horse, and rode into the hidden fourth line. It broke. The exposed Pompeian left was then rolled up. Pompey left the field for his camp and then abandoned it.
Tactics
The fourth line is the most-cited tactical reserve in ancient warfare, and its interest is that it was designed against a specific predicted manoeuvre rather than held as a general reserve. Caesar states that he told the cohorts what to expect and what to do. The instruction to thrust at the riders' faces is a detail that reads as authentic and is also exactly the kind of vivid particular a self-justifying memoir supplies.
Consequence
The senatorial cause lost its army and, within weeks, its leader. Resistance continued in Africa and Spain until 45 BCE, but the Republic as a functioning system of competing aristocratic power did not recover. Caesar was appointed dictator and was assassinated four years later.
Location
The plain near Pharsalus in Thessaly
Modern: Near Farsala, Thessaly, Greece
The region is certain; which bank of the Enipeus the battle was fought on has been argued since the nineteenth century and is not resolved.
Open questions
How reliable are the troop numbers?
They come almost entirely from Caesar. Appian and Plutarch give variants that may derive from Asinius Pollio, an eyewitness on Caesar's side whose history is lost. The two-to-one disparity is probably exaggerated and probably real in direction.
Which side of the Enipeus?
The topographical indications in Caesar do not fit the modern landscape unambiguously, and reconstructions place the battle on either bank. Unresolved.
Primary sources
Julius Caesar, The Civil War 3.82-99
Caesar's own account: the principal source, and written by the victor to justify himself to a Roman readership.
Plutarch, Life of Pompey 68-73
Preserves a tradition sympathetic to Pompey.
Appian, The Civil Wars 2.65-82
A later Greek account drawing on lost sources including Asinius Pollio, who was present.
How to read the evidence labels
- Evidence level: Documented
- Supported by a named primary text or by excavated material evidence.
- Evidence level: Probable
- Supported by strong inference that most specialists accept.
- Evidence level: Disputed
- Substantial specialist disagreement exists; competing readings are stated.
- Evidence level: Literary
- Belongs to poetic or mythological construction rather than to history.
- Evidence level: Mythological
- Belongs to shared religious or mythic tradition rather than to any single text.
- Evidence level: Unknown
- The available evidence is insufficient to decide.
These labels describe the status of the evidence, not our confidence in a conclusion. A claim marked Literary is not a claim we doubt; it is a claim about what kind of thing a poem is.