After the Roman defeat at Trebbia, the Roman Senate actually feared that the Carthaginian army, currently wreaking havoc in the countryside to the north would swoop down onto the gates of Rome itself. Rome had never been invaded by a large competent army. This was a first in Roman history. By now, he had defeated the Romans in a large skirmish at Ticinus. Then a 40,000 man force had been decimated at Trebia. This was a national emergency. So the Senate raised another army, recalled the loser at Trebbia, Toberius Sempronius Longus and appointed Gaius Flaminius and Gnaeus Geminius to lead a new attack. Geminius was given a new army and Flaminius was given what remained Longus’ force, of course to be rebuilt.
Hannibal was a thinker, a camophlage artist, a deceiver. He was master of executing bold unexpected maneuvers, and he was finally fulfiling the wishes of his father Hamilcar Barca, who emplored him to devote his life to the destruction of the Roman Empire. Hannibal was a master tactitcian. He had a huge mercenary army he paid and led from Spain. He had Gallic infantry. He had heavy African infantry and he had Numidian cavalry, arguably the best in the world. Hannibal also had a robust network of spies; he knew intelligence was the most powerful weapon one could wield, and thusly, his spies informed him that Flaminius was impetuous and could be easily provoked into headlong assaults. This would prove fortuitous for Hannibal and this is how he would play the Roman consul. The Carthaginian army moved south east through what is now known as Pischieto towards San Donato. This was difficult terrain, hilly, rocky, and thick with vegetation, and just north of Lake Trasemene. Polybius writes that Flaminius occupied a military encampment in the heart of the area he was sent to protect and as soon as all his troops were trained and assembled, he headed south to set up a defensive perimeter on the roads leading to Rome. Hannibal marched his troops faster and in turn forced Flaminius to put his own men into a forced march just to stay between the Carthaginians and Rome.
Once both armies set on either side of the lake’s northern edge, Hannibal immediately began pushing Flaminius’ buttons. Hannibal sent troops racing into nearby towns northeast of Flaminius to set fire to everything his troops could burn. In the hot Summer of July 217 BC, the woods around these towns were dry and the fire burned hard and smoke columns climbed so everyone could see the public humiliation of Flaminius who watched as the area he was sent to protect is razed. The Roman Senate pressured Flaminius to attack immediately, but his own advisors recommended sending large cavalry and light infantry raiding parties to perform a series of ambush attacks and wait until Geminius’ army arrived to join him. As it stood Hannibal commanded 40 to 50,000 and Flaminius commanded 30 to 40,000 men. Who knows why Flaminius made the decision to take the bait? Perhaps it was because Flaminius was seeped in the history of Roman conquering armies, embued with the confidence that comes from being surrounded by 40,000 orderly troops, the sound of war horns, the sight of a Roman Army – and the fact that he was egotistical at that, it all tolled one outcome: Flaminius decided to attack.
The problem was the landscape; it was incredibly difficult, there was no other easy way to move east of Trasemene to pursue Hannibal. Picket guards reconnoitered the area and discovered that there was a small defile like road that stretch east to west along the northern shore of Trasemene and this road was really to only way to go to pursue Hannibal.
That said, there was one more piece of intelligence Hannibal discovered on June 19th, 217 BC. Spies informed that every morning a thick fog from the lake covered the road. He gambled that this would be a good place to stage an ambush.
Hannibal fooled Flaminius by setting fake campfires to the northeast of the Trasimene in hills of Tuoro hoping that the hot head Flaminius would think he had located the Carthaginian army and rush through the defile. The Carthaginian forces were not in camp to the northeast, in fact they were deploying to the thick woods just north of the defile where the Roman Army was passing. To the west lay the Carthaginian cavalry, in the center was the Gallic light infantry and at the east of the defile was the Spanish and African heavy infantry. A 40,000 man army utterly quiet, awaiting the sounds of war horns.
On the morning of June 24th, 217 BC, Flaminius hurried his Roman force through the defile. As his 40,000 man force was stretched thin across the northern pass on the lake, Flaminius couldn’t help himself and decided to send a small raiding party to surprise the sleeping Carthaginian troops in the decoy encampment in Tuoro where he believed Hannibal’s troops settled. He felt now he had Hannibal cornered.
The fact was he had no idea where Hannibal’s huge army was. He was about to find out. The Roman Army won more often than it lost. But it was an Army whose tactics required large open plains, and interlocking heavy shields held by heavily armed infantry, easy for troops to march in step, and easy terrain for large cavalry formations. So not only were the Romans not deployed into their mandibles, they were hardly even armed; the arms carriers were behind most of their forces waiting to come out of the woods and move into battle array. Flaminius had also just split his force by sending raiders into the decoy camp.
The fog showed up and Hannibal’s troops were carefully and quietly hidden in the woods. Once the Romans were stretched out, and midway through the defile, Hannibal sprung his trap. The Carthaginians blocked the Western escape route with heavy cavalry and the Spanish and African infantry blocked the eastern escape route. The skirmish line extended the length of the 40,000 man army from the western edge of the lake to the east.
Close quarter combat ensued, unarmed or unarmored Romans faced light infantry and the struggle was desperate. But Flaminius’s troops had been caught with their pants down and 15,000 Romans were slaughtered in the ambush, many drowned trying to swim in heavy armor. 10,000 escaped, and about 6000 were taken prisoner.
Up until Cannae, Trasimene was the worst Roman defeat in history. The Romans were never more frightened of being overthrown. Hannibal spent over decade in the heart of Italy waging war and wreaking havoc. It would not be until 15 years later at Zama before he was thrown out of Rome for good.
The Second Punic War, 1886, Macmillan. Thomas Arnold.
The History of Rome, Livy The Romans in Spain, Methuen & Co., Ltd., 1939, C.H.V. Sutherland.