A 2,000-year-old sample of horse faeces has solved one of the ancient world's most enduring mysteries — how Carthaginian General Hannibal led an army of 40,000 men, as well as horses and elephants, across remote terrain and snow-covered Alps to surprise unsuspecting Roman forces.

Key points: Historians have long argued over how General Hannibal pulled off the military feat

Historians have long argued over how General Hannibal pulled off the military feat Scientists say the 2,000-year-old horse dung sample proves the exact route of the journey

Scientists say the 2,000-year-old horse dung sample proves the exact route of the journey 'Churned up layer' of peatland swamp also found could be caused by 'people or animals moving around over the top of it'

Historians have long argued over how General Hannibal, the commander-in-chief of the Carthaginian armies, pulled off this tactical masterstroke that almost saw him conquer the might of Rome.

It was, by most assessments, one of the greatest military feats in history.

The daring march was made from Spain via the French and Italian Alps, with an army numbering close to 40,000 men along with thousands of their horses.

Joining those forces for the hazardous journey were dozens of war elephants, beasts regarded as the tanks of classical warfare.

The Romans had thought the Italian peninsula was almost impregnable from the north so Hannibal's surprise attack caught them completely unprepared.

Professor Bill Mahaney, from York University in Toronto, Canada, led the international team that set out to retrace Hannibal's journey across the Alps.

The exact route of the journey has long been a source of controversy.

But the team's discovery of a 2,000-year-old horse dung sample, found on a remote mountain pass known as the Col de la Traversette, has scientists convinced they have found answers.

"This is very possibly the first time that dung and bacteria have ever been used as artefacts," Professor Mahaney said.

"One of the key environmental parameters was to find a blocking rock fall on these sides of the mountain, the Italian side. That led me to look at [the course] and watering places and foraging places for his animals and his troops."

Team hopes analysis will also yield evidence of elephant dung

The team then found a peatland swamp by the side of a stream and began to record data from it.

Who were the Carthaginians? Carthage was an ancient city on the north coast of Africa and is now a suburb in the city of Tunis, Tunisia.

Carthage was an ancient city on the north coast of Africa and is now a suburb in the city of Tunis, Tunisia. From the middle of the third century BC to the middle of the second century BC, Carthage fought a series of three wars with Rome, known as the Punic Wars.

From the middle of the third century BC to the middle of the second century BC, Carthage fought a series of three wars with Rome, known as the Punic Wars. When Carthage was eventually completely defeated by Rome, the site was plundered and burned.

When Carthage was eventually completely defeated by Rome, the site was plundered and burned. General Hannibal commanded the Carthaginian forces during the Second Punic War, between 218 BC and 201 BC. Source: Encyclopedia Britannica

"We pulled the data out and started to look at it and to my great amazement, we found a churned up layer," Professor Mahaney said.

"There's only two things that are going to churn a peatland — it's a hell of a lot of people or animals moving around over the top of it, or frost.

"So then I got interested in getting a microbiologist on board to start looking at bacteria in this because if we had animals doing this, there will be a lot of dung."

Microbiologist Chris Allen, from Queen's University Belfast, said after surveying the whole site, very few places were found where General Hannibal could have watered an army that large.

"We've sampled and used microbiology and chemistry and some pollen analysis to show which route he took," Mr Allen said.

The team hopes their analysis of the churned up mud found on the mountain pass may yet yield evidence of elephant dung as well, something that would silence any remaining doubters.

In the meantime, Mr Allen said, sifting through millennia-old faecal matter has also yielded other surprising benefits.

"We've learnt an awful a lot about the history and at the same time, we've been able to develop some very nice techniques for analysing soil, analysing sediments for key microorganisms that could be involved in lots of different things," he said.