In early December Scipio was encamped near the eastern bank of the Trebia River, south of Placentia. He had been reinforced by Tiberius Sempronius Longus, who assumed command as a result of Scipio’s injury. The Romans found themselves in a difficult position, with many of their own Gallic troops defecting to Hannibal. Still, having a camp on the high ground, they were in a strong position. Unfortunately for the Romans, Sempronius was eager for glory and not content to stand his ground. Scipio had warned Sempronius to avoid battle; a winter of training would improve his own force while months of inaction would send many Gauls home from boredom. Waiting months to attack, however, would also mean sharing the glory with a recovered Scipio. “And so,” writes Polybius, “since the time he chose of the engagement was not dictated by the facts of the situation but by his personal motives, his judgment was bound to be at fault.”
Capitalizing on the rash judgment of his enemy, Hannibal laid a trap for Sempronius. He placed his brother Mago with 1,000 infantry and 1,000 cavalry out of sight in the brush-covered valley with steep sides. He then sent a force of cavalry across the Trebia at dawn to harass the Romans and provoke an attack. When Sempronius ordered his men to chase the Numidians, the Romans formed their ranks in blowing snow and without the benefit of breakfast. Hannibal, on the other hand, had made sure his men were warm and fed. Sempronius pursued after the feigned retreat of Hannibal’s cavalry and crossed the cold river, swollen from recent rains, onto open ground. Typically, Roman armies approached battlefields in column, and deployed by wheeling the column to the right until it was parallel to the enemy. This took a lot of time, especially with troops who had not had a lot of time to train. Hannibal held his men back at their campfires, and they watched the Roman lines form up across a two-mile frontage, 36,000 men strong, with some 4,000 cavalry divided on the flanks. Finally, Hannibal deployed his 8,000 slingers and light pikemen to the front, leading 20,000 mixed Gauls, Spaniards, and Africans in a long line of infantry. His elephants were placed in front of each infantry wing, with his 10,000 cavalry split evenly on the far ends.
The infantry battle started as Sempronius had hoped—with the Roman infantry making consistent headway against the Gauls in Hannibal’s center. But the stronger Carthaginian cavalry gained control of the flanks. Hannibal’s light infantry, after assaulting the Roman lines, had moved to the flanks, and the Roman cavalry were, according to Livy, “buried under a virtual cloud of missiles hurled by the Balearic forces. In addition to this, the elephants standing at the extremities of the wings caused widespread panic, especially among the horses, which were terrified not just by the sight but also by their unfamiliar smell.” Still, the Roman infantry seemed to be holding up well. The ancient Roman historian Appian writes that the “foot-soldiers, although suffering much and weakened by cold, wet clothes, and want of sleep, nevertheless boldly attacked these beasts, wounded them, and cut the hamstrings of some, and were already pushing back the enemy’s infantry.”
Suddenly, Mago’s hidden force struck the Roman rear. Some 10,000 of the Romans managed to break through the Gauls in the Carthaginian center and flee north to Placentia, but the bulk of the army was either slaughtered or captured. Hannibal lost some 5,000 men, but soon made up those numbers with even greater local recruiting and more desertions from the Roman army.
“Outnumbered by the Romans, Hannibal had used the weather, the terrain, psychology and superior tactics to devastate a numerically superior enemy,” John Prevas writes. He had used the Roman disdain for “barbarians”—for so they considered the Gauls—to his advantage. Sempronius did everything wrong, following his emotions and ambition into a sleet storm, across a freezing river, and onto ground perfectly suited for Hannibal’s cavalry. Had Hannibal’s Gallic allies stood their ground, eight Roman and allied legions would have been destroyed. Still, it was bad enough.
Hannibal initiated the movement to contact with the raid by his Numidian light cavalry. Knowing Sempronius’s temperament, Hannibal succeeded in provoking a hasty attack, while his plan was well thought out. Using the terrain and weather, Hannibal also controlled the tempo of the engagement, forcing the Romans (because of their slow approach through the river and slow deployment) to fight while freezing, drenched, and hungry. Meanwhile, the Carthaginian force was well fed, rested, and better prepared for the cold (by oiling their bodies). Initially, the only surprise was the elephants’ effects on the Roman cavalry. However, once the armies were fully engaged, Mago’s unexpected attack at the Roman rear was devastating. That attack, coupled with the victory of Hannibal’s cavalry on both flanks, completed the envelopment. As mentioned, only the weakness of the Gallic infantry, and the Roman heavy infantry’s breaking through their lines, denied Hannibal a complete exploitation of the Roman force. No pursuit of the fleeing Roman soldiers ensued owing to the rapid deterioration of the weather.
Hannibal spent the winter resting his men and establishing an intelligence network to educate himself on the enemy geography and armies. The Roman government and people steeled themselves for another campaign. According to Polybius, “It is when the Romans stand in real danger that they are most to be feared, and this principle applies both to their public and to their private life.” By the spring of 217 BC, two more armies were in the field against Hannibal, one of 40,000, under Gaius Flaminius Nepos at Arretium (Arezzo), and a second of 20,000, commanded by Cnaeus Servilius Geminus on the Adriatic coast at Ariminum (Rimini). They blocked the two main roads southward and were close enough to support each other if one should contact the invaders.
However, Hannibal had won two victories with flanking moves on the battlefield, and he now launched yet another strategic flanking movement. The Carthaginian troops crossed over the Apennines well away from the two waiting armies. As in the march through the Alps, what route they took through the Apennines is not exactly known, though it is likely they followed the Trebia toward its source. Local legend has Hannibal’s armies camping in the region of some of the towns high in the Trebia Valley. Marching over the crest of the Italian Alps, they would have emerged near Genoa and then headed south. By this time Hannibal was down to but one elephant, the others having perished (depending on one’s source) at the Battle of the Trebia, or during an extremely cold winter.
This northerly mountain crossing did not unduly concern Flaminius, however, for the Carthaginians would have to come to him anyway; they could not possibly cross the swamps north of the lower stretches of the Arno during the spring floods. Hannibal proceeded to do exactly that, as apparently his crossing of the Alps had failed to educate Flaminius as to the depth of Hannibal’s skill and daring. Four days and three nights in a sucking morass cost him more soldiers and his final elephant. The soldiers underwent unbearable suffering, as the trailing troops would be obliged to cross swampland already disturbed by the previous soldiers. This resulted in loud complaining and could possibly have even ended in mass desertion but for Mago’s cavalry bringing up the rear and blocking any such attempt. The horses themselves suffered distemper in their hooves and collapsed in massive numbers. The soldiers also were victim to such diseases are found in swamps, with Hannibal himself losing an eye to an infection. They emerged to the west of Flaminius and with an open road to Rome, to the disbelief of the opposing forces.
Battle of Lake Trasimene, 217 BC – art by Giuseppe Rava ~ The Carthaginians under Hannibal defeated the Romans under the consul Gaius Flaminius. The battle is one of the largest and most successful ambushes in military history. A Numidian is in the foreground, Gaulic cavalry in the background, to the right you can see Roman legionaries and the horseman in the middle appears to be an officer of the Romans.
The Battle of Lake Trasimene
Having dried out, Hannibal attacked east instead of south, raiding Faesulae, near modern Florence. He was learning about the mind of his enemy. As Livy put it, “He thereupon proceeded with a very thorough and detailed enquiry into the consul’s strategy and way of thinking, into geography and routes of the area and its capability of providing supplies, and into everything else that it was valuable for him to know.” None of the Roman writers, on the other hand, are complimentary about Flaminius. Although he had led an unspectacular foray against the Gauls several years earlier, Appian describes him as “inexperienced in war (for he had been wafted into power on a popular breeze).” Polybius describes him as “a mere mob-orator and demagogue, with no ability for the actual conduct of military affairs, and was moreover unreasonably confident in his resources.” According to Livy, “It was therefore perfectly clear that Flaminius would have no regard for god or man, and that his conduct would be characterized throughout by arrogance and lack of caution.”
Having taken the measure of his opponent, Hannibal led his army southward past Arretium toward Cortona. The Carthaginian troops set fire to the countryside, burning lands near enough to the Roman camp that Flaminius could not help but see the smoke. The Roman commander was infuriated. His officers advised him to await Servillius’s 20,000 men before launching an attack, but Flaminius would have none of it. So sure was he of victory that he ignored not only advice but common sense. His promises motivated the civilians, however, if not his officers. “Indeed, he had even created such over-confidence among the populace that the soldiers were outnumbered by crowds of camp-followers who accompanied his march in the hope of finding plunder,” wrote Polybius, “and carried chains, fetters and other such gear with them.”
Hannibal’s scouts, meanwhile, had found one of the most perfect ambush sites in Italy, if not the world—on the north shore of Lake Trasimene, south of Cortona. Overlooking the northwestern part of the lake, at the site of modern Tuoro, is a chain of hills in a semicircle with the ends of the range almost touching the lake shore. Livy is enthusiastic about the choice: “Between the two there is no more than a narrow pathway, almost as if just enough space had been deliberately left for Hannibal’s purpose!” Upon these hills Hannibal stationed his army, and waited for Flaminius to march his men along the road by the lakeshore. On the morning of 21 June 217 BC, the Roman army marched into the defile, the hilltops covered with Hannibal’s men hidden by the morning mist. Once the Romans were stretched out along the road, the onslaught from the hills was unstoppable. Polybius reports that Flaminius died quickly and without credit to himself. Livy’s description makes his last stand heroic. Without time to deploy and in limited visibility, a credible defense was impossible. Some 6,000 men of the advanced guard did fight their way through the light infantry at the eastern end of the valley, but the remainder were lost. Some 15,000 were killed in battle or drowned in the lake and a similar number taken captive. Hannibal’s loss was roughly 2,500 men.
For the movement to contact, Hannibal first engaged in an approach march since he knew exactly where Flaminius was located. Not wanting to fight on ground the enemy had chosen, Hannibal bypassed Arretium and launched raids across the area that destroyed enemy resources and provoked their commander. Flaminius followed the billows of smoke to the very ground Hannibal had chosen. Livy describes the Roman approach: “Flaminius had reached the lake at the sunset of one day, and, when it was barely light on that which followed, he went through the defile without reconnoitering.” Thus was Hannibal’s surprise complete. The attack concentrated every element of his force on a narrow target. He had chosen the terrain perfectly, and the weather once again was on his side. There was no need to regulate the tempo of the battle: speed was everything. The Roman army, unready for battle and unable to even see their attackers until too late to respond, was completely vulnerable. Hannibal’s one failing was allowing the 6,000-man Roman vanguard to bull their way through his light infantry at the eastern end of the battlefield. Though they could hardly be expected to stand an assault of heavy infantry, it is difficult to know where else he could have placed them. Nevertheless, Hannibal made good the loss in the pursuit, and the vanguard were surrounded and captured the following day.
To complete the rout, Hannibal sent his cavalry eastward to scout the approach of Servillius’s force, and they ambushed and destroyed the Roman cavalry advance guard. News of this double defeat was yet another shock to Roman hopes, and Polybius’s comment on their reaction is rather different from his view after the Trebia battle, when he valorized Roman toughness: “In times of danger the Romans will go to astonishing lengths to propitiate both gods and men, and there is no ceremony of this kind which they regard as unbecoming or beneath their dignity.”
