What happened
After defeats at the Trebia and Lake Trasimene, Rome abandoned the delaying strategy of Fabius Maximus and raised an exceptionally large consular army to force a decision.
Hannibal drew up with his Spanish and Gallic infantry in a convex line bulging toward the Romans, his veteran African infantry in column on either flank, and his superior cavalry on the wings.
The Roman infantry pushed the Carthaginian centre back, as it was intended to. The convex line became concave. As the Romans pressed into the pocket their front narrowed and their mass became unusable.
The African infantry turned inward on both flanks. The Carthaginian cavalry drove the Roman horse from the field, rode around the rear and closed the encirclement. The Roman army was surrounded in a space too small to fight in and killed over the course of a day.
Tactics
The manoeuvre requires a commander to plan for his own centre to give way and to trust that it will retreat without breaking — which is why it has been imitated more often than it has been executed. Its precondition was cavalry superiority: without control of the flanks and rear the encirclement cannot be closed. Cannae is studied less as a template than as a demonstration that a numerically inferior army can convert an enemy's mass into a liability.
Consequence
Rome lost perhaps a fifth of its available male citizens of military age in a single day, along with a serving consul, two former consuls and some eighty senators. Several southern Italian communities and Capua defected to Hannibal, and Macedon entered the war against Rome. Rome refused to negotiate, raised new armies, and returned to the Fabian strategy. The war was decided in Spain and Africa rather than in Italy.
Location
The plain of the Aufidus river near Cannae, in Apulia
Modern: Near Barletta, Puglia, Italy
The general location is accepted. Which bank of the Aufidus the armies stood on is disputed, and the river has shifted its course.
Open questions
How many Romans died?
Polybius gives 70,000, Livy about 48,200. The figures cannot be reconciled and both authors are drawing on earlier annalistic material now lost. The scale of the disaster is not in question; the number is.
Was Varro solely responsible?
The tradition blames the plebeian consul Varro and exculpates the aristocratic Paullus, who died on the field. The pattern is suspiciously convenient for the senatorial families whose accounts fed the historians, and modern scholarship treats the apportionment of blame as a product of Roman politics rather than a finding.
Primary sources
Polybius, Histories 3.107-118
The fullest and earliest surviving account, by a Greek writing at Rome with access to the Scipionic circle.
Livy, History of Rome 22.34-54
A later and more rhetorical Latin account, preserving variant figures and traditions.
Plutarch, Life of Fabius Maximus 14-17
Preserves the political argument at Rome before and after the battle.
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.