It is one of the most exciting chapters in military history. In 218 BC C., the Carthaginian general Hannibal crossed the Alps with a squadron of 37 war elephants to invade Italy.

While we can’t say what route he used to cross this rugged terrain, a new study published today in the journal Proceedings of the National Academy of Sciences (PNAS) offers some new clues. The new analysis shows which of Hannibal’s potential routes would have been least taxing for his 40,000 men, 7,000 horses and 37 war elephants. Your best option would probably have been the Col de la Traversette, a pass with an altitude of 9,669 feet on the border between Italy and France.

Why did Hannibal cross the Alps?

Hannibal came from Carthage, an ancient city-state and dominant Phoenician empire in modern-day Tunisia. During the Second Punic War, Carthage controlled the coast of North Africa and the Iberian Peninsula (present-day Spain and Portugal). Rome attempted to use its naval dominance to force its rival to surrender.

To bring the war directly to the gates of Rome, Hannibal led his army across the Alps from France to Italy. This was easier said than done, as it required traversing rugged terrain, snow and ice, while surviving mountain passes controlled by local tribesmen who could attack them from above. However, traversing the mountain range meant he could avoid Rome’s fearsome navy in the Mediterranean and its military garrisons on land.

Only two main sources from the event survive and they were written 20 and 160 years after the event. And since there is no archaeological evidence available, interpreting the events of the crossing is difficult. All modern theories depend on the interpretation of the three toponyms used by the writer Polybius (Island, Skaras and Allobroges) and the broader range of toponyms of tribes and places written by Livy. Scholars then compare those places to current geographic knowledge.

According to Livy’s account, Hannibal marched his army across the Alps in just 16 days. However, Hannibal’s entire military campaign lasted approximately two months and ended up being very costly. Hannibal lost more than 20,000 men and Carthage ultimately lost the war.

It is still unclear why he used elephants for the crossing. It is possible that his intention was to provide a tactical element of surprise during his early battles against the Romans. He may also have hoped that the wonder of seeing these elephants would help him recruit the Celts of northern Italy to his side.

Energy saving

In this new study, a team from the University of Oxford in the United Kingdom, the German Center for Integrative Biodiversity Research (iDiv), and the Friedrich Schiller University of Jena in Germany evaluated competing theories about which route Hannibal took over the mountains. Previously, historians believed he may have taken the Col du Clapier, an 8,127-foot-high mountain pass between Savoy, France, and Piedmont, Italy.

The team used route models and elevation data to estimate the energy cost of each potential alpine crossing. They used data collected on how much energy modern African elephants would consume to make a crossing like this, based on their body mass and the terrain.

Their results suggest that the Col de la Traversette would have been the shortest and most energy efficient route. Compared to the Travesette route, traveling the Col de Montgenèvre would have required 11 percent more energy. Col du Clapier would have needed 16 percent more, while Col du Mont Cenis needed 19 percent more energy.

The team’s models also highlight the physical challenge of moving an army (and elephants) through the mountains. Had they taken the Traversette route, the men would have lost 19 percent of their body fat reserves, which may be a factor behind the high human mortality rate later in the battle. Hannibal lost approximately 20,000 men by the end of the campaign.

Surprisingly, the new analysis suggests that war elephants would have fared better in the crossing. The elephants would have only lost four percent of their fat reserves, according to the team’s models. These high energy reserves probably explain why many, if not most, of the elephants survived.

“The question of Hannibal’s exact route has been debated for generations,” Dr. Emilio Berti, a co-author of the study and a biologist at the German Center for Integrative Biodiversity Research and the Friedrich Schiller University of Jena, said in a statement.

“The new analysis does not remove all ambiguity, but it strengthens the case for the Traversette route by showing that it would better accommodate the demands of moving a large army that included elephants through extremely difficult alpine terrain.”

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