Outnumbered nearly 2-to-1, Hannibal still surrounded and destroyed a Roman army in a day

At Cannae in 216 BC, Hannibal let his center sag backward under Roman pressure while his flanks and cavalry swung around the sides, closing a ring around the entire Roman force. Tens of thousands of Roman soldiers were killed in a single day, one of the deadliest battlefield losses in history. Cannae is still taught at military academies today as the textbook example of a double envelopment, and inspired commanders from Frederick the Great to Norman Schwarzkopf.

— Polybius, The Histories — 2nd century BC account of the Second Punic War