Battle of Cannae

The Battle of Cannae was a key engagement of the Second Punic War between the Roman Republic and Carthage, fought on 2 August 216 BC near the ancient village of Cannae in Apulia, southeast Italy. The Carthaginians and their allies, led by Hannibal, surrounded and practically annihilated a larger Roman and Italian army under the consuls Lucius Aemilius Paullus and Gaius Terentius Varro. It is regarded as one of the greatest tactical feats in military history and one of the worst defeats in Roman history, and it cemented Hannibal's reputation as one of antiquity's greatest tacticians.

Having recovered from their losses at Trebia and Lake Trasimene, the Romans decided to engage Hannibal at Cannae, with approximately 86,000 Roman and allied socii troops. They massed their heavy infantry in a deeper formation than usual, while Hannibal used the double envelopment tactic and surrounded his enemy, trapping the majority of the Roman army, who were then slaughtered.

Source: Wikipedia