Lago Trasimeno is the largest lake on the Italian peninsula. It abuts the Umbria-Tuscany border roughly between the ancient city-states of Perugia and Siena. The surrounding countryside is bucolic and peaceful. More than 2,200 years ago, however, it was the site of one of the classical era’s bloodiest battles.

At the outset of the Second Punic War (218–201 BC) between Carthage and Rome, the Carthaginian commander Hannibal Barca invaded Italy from Spain by boldly marching over the Alps in the fall of 218 BC with a force of some 20,000 infantry and 6,000 cavalry. That winter, while Hannibal rested his troops in the Po River valley and recruited local reinforcements, his spies reported the Romans were fielding two new armies against him under the consuls Gaius Flaminius, with some 30,000 troops, and Gnaeus Servilius Geminus, with 20,000.

By early spring 217 BC Hannibal was ready to strike, while the consular armies moved to block the two main roads leading to central Italy and Rome—Servilius on the west coast at Ariminium (presentday Rimini), Flaminius on the Etruscan plain at Arretium (Arezzo). Hannibal drove south to Bononia (Bologna), seemingly oblivious of the waiting Roman armies, then made a surprise crossing of the snowcapped Apennine Mountains. Descending onto the Etruscan plain, the Carthaginians struggled through the treacherous marshes around the Arno River, generally considered impassable during spring flooding. Rapidly moving south, Hannibal veered around Flaminius’ left flank to threaten Rome. By ravaging the surrounding countryside, he hoped to draw the Roman consul into battle. Recognizing the threat to Rome, Flaminius took the bait and pursued. Hannibal, meanwhile, deployed a cavalry force to block any support elements Servilius might send.

Late on June 20 Hannibal and Flaminius made camp along the north shore of Lake Trasimeno. Hannibal had set his trap on terrain ideally suited for a large-scale ambush. The hills north of Trasimeno form a punchbowl around a flat plain stretching some four miles along the lakeshore. East and west of the plain the semicircular ridgeline runs almost to the shore. The Roman camp was near the northwest shore, just outside the entrance to the punchbowl. The Carthaginian main camp was in the hills to the east, overlooking the plain.

Hannibal now had more than 50,000 troops, including some 10,000 cavalry. During the night he concealed his forces in the forested hills ringing the plain. The west entrance to the plain was a narrow defile that ran between the lake and the high ground. There Hannibal concealed heavy cavalry and infantry to seal off the killing ground after the Romans passed through the defile.

Early on June 21 Flaminius, believing himself in pursuit of a rapidly fleeing enemy, pushed his troops through the defile with no reconnaissance and no advance or flank guards. Even the weather conspired against the Romans, as a heavy fog rolled in off the lake to conceal the surrounding hills. The lead elements passed through the defile and marched onto the plain along the lakeshore. Nearing the east end of the plain, they made contact with a Carthaginian blocking force. Assuming he had caught Hannibal’s rear guard, Flaminius sent word back to close up the column. The Romans pressed forward until the entire force was within the punchbowl. Only then did Hannibal spring the trap.

The Carthaginians attacked simultaneously from all sides, hitting the Romans so hard and fast that even the units on relatively open ground had no time to deploy into battle formation. Hannibal’s onrushing men cut down the Romans before they could draw their swords, while his heavy cavalry overwhelmed the Roman elements still in the defile. Driven into the lake, many legionaries drowned under the weight of their armor.

The carnage lasted more than three hours. By the time it was over 15,000 Romans lay dead, including Flaminius, and 5,000 had been captured. Some 10,000 managed to escape into the hills, eventually taking news of the great defeat back to Rome. Hannibal’s loses amounted to some 2,500 killed. Little more than a year later, on Aug. 2, 216 BC, Hannibal handed the Romans another punishing defeat, at Cannae, a battle that still fires the imagination of military tacticians.

The battlefield at Lake Trasimeno, a two-hour train ride from Rome, is one of the best preserved of the classical era. A hiking trail around the perimeter of the field takes about three hours to complete. One segment follows the stretch of ancient Roman roadway over which Flaminius and his troops marched through the western defile to their doom. Note that the lake itself has receded from the level it was in Roman times, thus the gap between the hills and the shore presented Flaminius and his ill-fated legionaries with an even tighter bottleneck than that which appears today.


Originally published in the January 2014 issue of Military History. To subscribe, click here.