Battle of Lake Trasimene.

• 217 BC – The Romans, led by Gaius Flaminius, are ambushed and defeated by Hannibal at the Battle of Lake Trasimene.
• The Battle of Lake Trasimene (June 21, 217 BC, April on the Julian calendar) was a major battle in the Second Punic War. TheCarthaginians under Hannibal defeated theRomans under the consul Gaius Flaminius. The battle is one of the largest and most successful ambushes in military history.
  The Romans, greatly alarmed and dismayed by Tiberius Sempronius Longus’ defeat at Trebia, immediately made plans to counter the new threat from the north. Sempronius returned to Rome and the Roman Senate resolved to elect new consuls the following year in 217 BC. The new consuls were Gnaeus Servilius Geminus and Gaius Flaminius, the latter was under threat of recall from the Senate for leaving Rome without carrying out the proper rituals after being elected consul.  The Senate commissioned Servilius to replace Publius Cornelius Scipio and take command of his army, while Flaminius was appointed to lead what remained of Sempronius’s army. Since both armies had been weakened by the defeat at Trebia, four new legions were raised. These new forces, together with the remains of the former army, were divided between the two consuls. After the battles of Ticinus and Trebia, Flaminius' army turned south to prepare a defence near Rome itself. Hannibal immediately followed, but marched faster and soon passed the Roman army. Flaminius was forced to increase the speed of his march in order to bring Hannibal to battle before reaching the city. Another force under Servilius was due to join Flaminius.
  Hannibal, emerging from another brilliant victory, had successfully planned and executed the greatest ambush in history. News of the defeat caused a panic in Rome. Quintus Fabius Maximus was electeddictator by the Roman Assembly and adopted the"Fabian strategy" of avoiding pitched conflict, relying instead on low-level harassment to wear the invader down, until Rome could rebuild its military strength. Hannibal was left largely free to ravage Apulia for the next year, until the Romans ended the dictatorship and elected Paullus and Varro as consuls. The result would be the Battle of Cannae, the worst defeat the Romans would suffer throughout the Second Punic War.
  ^{As Hannibal passed Lake Trasimene, he came to a place very suitable for an ambush, and hearing that Flaminius had broken camp and was pursuing him, made preparations for the impending battle. To the north was a series of heavily forested hills where the Malpasso Road passed along the north side of Lake Trasimene. Along the hill-bordered skirts of the lake, Hannibal camped where he was in full view of anyone entering the northern defile, and spent the night arranging his troops for battle. Below the camp, he placed his heavy infantry (Iberians, Celts and Africans) upon a slight elevation. Here, they had ample ground from which they could charge down upon the head of the Roman column on the left flank, when it should reach the position. His cavalry and Gallic infantry were concealed in the hills in the depth of the wooded valley from which the Romans would first enter, so that they could quickly sally out and close the entrance, blocking the Roman route of retreat. Then he posted his light troops at intervals along the heights overlooking the plain, with orders to keep well hidden in the woods until signalled to attack. In addition, the night before the battle commenced, Hannibal ordered his men to light campfires on the hills of Tuoro, at a considerable distance, so as to convince the Romans that his forces were further away than they actually were.}
  ^{Before this could happen, Hannibal lured Gaius Flaminius' force into a pitched battle, by devastating the area Flaminius had been sent to protect. Polybius wrote that Hannibal calculated that he could draw out Flaminius into battle and that "no sooner had he left the neighbourhood of Faesulae, and, advancing a short way beyond the Roman camp, made a raid upon the neighbouring country, then Flaminius became excited, and enraged at the idea that he was despised by the enemy: and as the devastation of the country went on, and he saw from the smoke that rose in every direction that the work of destruction was proceeding, he could not patiently endure the sight." At the same time, Hannibal tried to sever the allegiance of Rome’s allies, by proving that the Republic was powerless to protect them. However, Flaminius remained passively encamped at Arretium. Unable to goad Flaminius into battle, Hannibal marched boldly around his opponent’s left flank and effectively cut Flaminius off from Rome (thereby executing the earliest recorded deliberate turning movement in military history). Still, Flaminius stubbornly kept his army in camp. Hannibal decided to march on Apulia, hoping that Flaminius might follow him to a battlefield of his own choosing.}
  ^{Flaminius, eager to exact revenge for the devastation of the countryside, and facing increasing political criticism from Rome, finally marched against Hannibal. Flaminius, like Sempronius, was impetuous, overconfident, and lacking in self-control.  His advisors suggested that he send only a cavalry detachment to harass the Carthaginians and prevent them from laying waste to any more of the country, while reserving his main force until the other consul, Servilius, arrived with his army. However, it proved impossible to argue with the rash Flaminius. Livy wrote that "Though every other person in the council advised safe rather than showy measures, urging that he should wait for his colleague, in order that joining their armies, they might carry on the war with united courage and counsels... Flaminius, in a fury... gave out the signal for marching for battle."}