On a June morning in 217 BC, the Roman consul Gaius Flaminius led his army of approximately 25,000 men along the northern shore of Lake Trasimene in Etruria, moving through a narrow defile between the lake and the hills, in fog thick enough to prevent the reconnaissance that might have revealed what Hannibal had placed along the surrounding heights. Within three hours, roughly 15,000 Romans were dead, Flaminius himself among them, killed in the confusion before any coherent Roman formation had been established. The survivors fled into the lake and drowned or were captured. It was the largest ambush in ancient military history, executed with a precision that modern military historians still use as a case study in the application of terrain and concealment.