One of the most famous military campaigns of all time is the crossing of the Alps by Hannibal more than 2,200 years ago. The bold Carthaginian general led infantry, cavalry, and 37 elephants across the Italian mountains to face off against the Romans. And now, thanks to science, we know which way he chose to cross.

An international team of researchers has discovered a mass animal deposit located near the Col de la Traversette, a pass about 3,000 meters (9,840 feet) above the sea level. The scientists were able to date the deposit to 218 BCE thanks to an environmental analysis of the soil.

The team has studied this area since 2011 as a potential place where the Carthaginian army might have rested. The area is rich in vegetation that could have been used for the horses and mules, and it is one of the several possible routes the general might have taken.

Deep in the ground, the researchers found that there was a mixture of plant fibers, mud, and finer grained soil. The findings, reported in the journal Archaeometry, suggest that the soil had been significantly disturbed and then it was compacted. No other alpine bog has such a soil, and this cannot be explained by grazing cattle or weather phenomena.

"The deposition lies within a churned-up mass from a 1-meter [3.3-feet] thick alluvial mire, produced by the constant movement of thousands of animals and humans,” Dr. Chris Allen from Queen's University Belfast said in a statement.

“Over 70 percent of the microbes in horse manure are from a group known as the Clostridia, that are very stable in soil – surviving for thousands of years. We found scientifically significant evidence of these same bugs in a genetic microbial signature precisely dating to the time of the Punic invasion.”

Hannibal’s descent into Italy was one of the major events of the Second Punic War, which was eventually won by the Romans in 201 BCE.

The route through Col de la Traversette (a simple map is available on The Telegraph) was first proposed by Sir Gavin de Beer in 1974, but had not previously been widely accepted by the academic community due to a lack of concrete evidence.