Battle of Lake Trasimene

The Battle of Lake Trasimene was fought when a Carthaginian force under Hannibal Barca ambushed a Roman army commanded by Gaius Flaminius on 21 June 217 BC, during the Second Punic War. The battle took place on the north shore of Lake Trasimene, to the south of Cortona, and resulted in a heavy defeat for the Romans.

War had broken out between Rome and Carthage early in 218 BC. Hannibal, ruler of the Carthaginian territories in south-east Iberia, marched an army through Gaul, crossed the Alps and arrived in Cisalpine Gaul later that year. The Romans rushed reinforcements north from Sicily but were badly defeated at the Battle of the Trebia.

Source: Wikipedia