How Hannibal crushed Rome at Lake Trasimene

In order to understand how Hannibal won the Battle of Lake Trasimene, it is important to have some context about the situation leading up to the battle.

At the time, Rome and Carthage had been engaged in a bitter conflict known as the Second Punic War.

It began in 218 BC when the Carthaginian general Hannibal had marched his army from Spain, through southern France, across the Alps, and into Italy with the goal of defeating the Roman Republic.

Once in Italy, Hannibal had successfully convinced some Galic tribes in the Po valley to join his forces.

Then, Rome had suffered two defeats against Hannibal's forces at the battles of Ticinus River and Trebia River, both in 218 BC

Following these two defeats, the city of Rome was in turmoil. When winter broke at the start of 217, the two new Roman consuls for that year, Gnaeus Servilius Geminus and Gaius Flaminius, knew that they needed to achieve a significant victory to rid themselves of this dangerous threat.

Prior to the war, Gaius Flaminius had been instrumental in improving Roman infrastructure, including the construction of the Via Flaminia road, which would later play a strategic role in Roman military logistics.

By the time he was elected consul for 217 BC, eleven Roman legions were in service and Flaminius rode north to the city of Arretium, where his army was waiting for him.

During the winter months, Hannibal had camped in northern Italy to protect his forces from the harsh weather.

When spring began in 217 BC, he led his army across the Apennines mountains and into the marshes around the Arno River in Etruria, towards Rome.

Hannibal hoped that by moving through this inhospitable terrain that he might move past the Roman army in Arretium undetected.

However, this was a dangerous strategy, as it meant his army would be vulnerable to disease and attack from enemy forces if they were discovered.

The march through the marshes proved difficult due to flooding caused by the melting winter snows. 

Unable to find firm ground to make camp, Hannibal kept his men moving for four consecutive days before they could rest.

Hannibal himself developed an eye infection during this time and lost sight in his right eye.

Ultimately though, this move paid off and Hannibal's army arrived at the town of Cortona, south of Flaminius' base.

The Carthaginians gathered food and supplies and then burnt and pillaged the area. Hannibal was hoping to force a reaction from Flaminius. 

The sudden appearance of the Carthaginians behind his forces surprised Flaminius and he began to panic.

Flaminius took Hannibal's bait and ordered the Roman army to leave Arretium at once and engage the Carthaginians before they could cause too much damage to the Roman towns.

However, once Hannibal saw the Roman forces approaching, he began moving his own troops towards Lake Trasimene, where he hoped to lure Flaminius into a trap.

Lake Trasimene's strategic location, with its narrow northern shore flanked by hills, made it an ideal spot for Hannibal to set his ambush.

Hannibal spent several days scouting out the area around Lake Trasimene before the battle.

He was looking for a place where he could set up an ambush for the Romans. When he found the perfect spot, he began to prepare for the battle.

The Roman army numbered around 30,000 men. The Carthaginian army numbered more than 50,000 men. 

Hannibal divided his army into three parts and ordered his forces to take positions along the hills on the north side of the lake.

The first group he positioned on high ground above the Roman army's path. The second part he positioned behind a group of trees that were in front of the Roman army's path.

And finally, the third he positioned behind a hill that was next to the Roman army's path.

When everything was in place, Hannibal waited for the Romans to arrive.

On June 24th, 217 BC, Hannibal and his army met the Roman army at Lake Trasimene.

As the Roman army approached, they had no idea that they were walking into a trap. This was because two factors limited their view of the battlefield.

Firstly, Hannibal had positioned his troops strategically around the northern edge of the lake. 

Here, the surrounding hills were covered with thick forests, which hid Hannibal's men.

Secondly, an early morning fog had crept in from the lake as the sun rose, which obscured the landscape.

All too late, when the Roman soldiers had arrived on the lake's shore, did they realise that they had marched into a trap.

The first part of Hannibal's army opened fire on the Romans from their position on high ground.

This caused the Romans to panic and start to retreat back along the path that they came from.

But as they retreated, they ran into the second group of Hannibal's army, which was waiting for them behind the group of trees.

The Romans could not advance to the south, because the lake was too broad to swim across; they were unable to go any farther east, where Hannibal's light-armed soldiers stood guard and blocked their path.

There was also no way back since Gauls in Hannibal's army guarded the return route.

The Roman army was surrounded and completely outnumbered. They had no choice but to stand and fight.

On command, Hannibal ordered his army to charge down the hillside and slaughter the trapped Roman soldiers.

After almost three hours of fighting, the Roman army was annihilated and Flaminius himself was killed. 

The Carthaginians emerged victorious in one of the most decisive battles of the Second Punic War. At least 15,000 Romans perished. 

Since Hannibal wanted to break up the Roman alliance system that gave them control over the Italian peninsula, the Roman allies who were captured were treated well by him.

He encouraged captives to return to their towns throughout Italy and spread the news that Hannibal would welcome them into his army if their changed allegiance from Rome to Carthage.

In the aftermath of the battle, Hannibal continued his march towards Rome.

However, he quickly became frustrated that very few towns accepted his offer to change sides.

Most allied towns stayed loyal to Rome. This meant that Hannibal's army remained in hostile territory, with limited allies that were willing to provide him with food and shelter.

In response to the defeat at Lake Trasimene, the Roman Senate appointed Quintus Fabius Maximus as dictator, and ordered him to find a way to save Rome from Hannibal.

Fabius, knowing that Hannibal had to rely upon limited supplies and allies in the region, decided to use a strategy of attrition to try and wear down the Carthaginians.

Fabius refused to face Hannibal in open combat again. His cautious tactics that earned him the nickname 'Cunctator,' meaning 'the Delayer.'

However, Rome became frustrated with Fabius' indirect approach to victory and eventually replaced him with more aggressive commanders who were willing to fight Hannibal again.

Even though Hannibal would go on to win even more victories against Rome, particularly at Cannae in 216 BC, the fact that his armies needed to remain on military alert for potential attacks throughout Italy, placed a constant drain on resources and morale.