48 BC
Battle of Pharsalus
The setting
Near Pharsalus, Thessaly, Greece (Enipeus river plain)
Open plain bordered by the Enipeus river on one flank and hills on the other; both armies anchored a flank on the river, leaving the opposite (open) flank to be decided by cavalry.
Reveal the outcome
Recorded sidePompeians / Optimates (Pompey the Great)
Recorded resultdefeat
Decisive Caesarian victory; Pompey fled and was later killed in Egypt
How the atlas explains it
Anticipating that Pompey would use his huge cavalry advantage to envelop the open right flank, Caesar concealed a fourth line of veteran cohorts behind it. When Pompey's cavalry charged and scattered Caesar's outnumbered horse, the hidden cohorts rose and thrust their pila at the riders' faces, panicking and routing the cavalry. The reserve then wheeled into Pompey's exposed left wing while the disciplined Caesarian legions broke the infantry; Pompey fled the field.
What followed
Decisive battle of Caesar's Civil War; broke the senatorial/Optimate cause and made Caesar master of the Roman world, leading to his dictatorship and the end of the Republic. Pompey fled to Egypt, where he was murdered.