When Napoleon Bonaparte was infamously defeated by Britain’s Duke of Wellington at Waterloo in 1815, the bitter conflict left a bloody battlefield littered with thousands of corpses.

But what happened to all those dead bodies?

That is what a team of international military veterans hope to find answers to later this month.

The team, including serving personnel, archaeologists and volunteers, will work at the Mont-Saint-Jean site in Waterloo/Braine l’alleud border in Belgium to uncover the full extent of the burial pit.

In doing so they hope to get closer to solving that age-old mystery of what happened to the missing bodies of the Waterloo dead.

The battle was one of the deadliest of the century and marked the final defeat of Napoleon, who conquered much of Europe in the early 19th century.

Napoleon’s forces were defeated by the Prussians and the British (led by the Duke of Wellington) and it marked the end of his reign and of France’s domination in Europe. Napoleon ended up in exile on the island of Elba in the Mediterranean.

By some estimates, the French suffered almost 40,000 casualties (including dead, wounded or taken prisoner), while British and Prussian casualties numbered some 22,000. An estimated 20,000 men — most of them French soldiers — died in the Battle of Waterloo.

This all made for a monumental clean-up operation.

One contemporary account, by a certain Major W.E. Frye, described the battlefield on June 22 1815 as “a sight too horrible to behold.” Frye recounted “the multitude of carcasses, the heaps of wounded men with mangled limbs unable to move and perishing from not having their wounds dressed or from hunger.”

There are reports of local peasants being hired for clean up task, burying the dead of allies in mass graves and pits and burning the French corpses. A visitor to Hougoumont reported seeing burning pyres “fed solely by human fat.”

While more than 20,000 men are believed to have died during the battle, only two bodies have actually ever been discovered.

Professor Tony Pollard, Director of the Centre for Battlefield Archaeology at the University of Glasgow, and one of those involved in the latest dig, used written accounts and artwork from early visitors to conclude that deceased soldiers were buried in several mass graves, each containing thousands of corpses.

It is believed, he has noted, that people commonly looted human bones and sold them to make fertilizer. One clipping from The London Observer in 1822 estimates that “more than a million bushels of ‘human and inhuman bones’ were imported from the continent of Europe into the port of Hull.”

Later this month, the support charity Waterloo Uncovered will be carrying out a “targeted” excavation at Mont-Saint-Jean farm in Belgium’s Brabant Walloon, which served as Wellington’s field hospital during the battle.

In 2022, the charity made its most important discovery to date at the farm: a human skeleton, only the second complete human skeleton ever excavated on the Waterloo battlefield. Also discovered at the site were the amputated limbs of wounded men and the skeletons of three horses, leading archaeologists to suspect that they have only scratched the surface of what is likely to be a much larger feature.

From September 3 to 13, an international team of military veterans, serving personnel, archaeologists and volunteers will continue work at Mont-Saint-Jean to uncover the full extent of the burial pit, and in doing so will get closer to solving the mystery of what happened to the missing bodies of the battle.

Historical evidence points towards a grisly end for many of the skeletons from the battle, with contemporary news articles suggesting that they were dug up and ground down to be used as fertiliser and in the production of sugar, making the discovery of skeletons on the battlefield a highly unusual and historically significant occurrence.

Professor Pollard, who serves as the project’s Archaeological Director, said: “It’s an incredibly exciting site – the presence of amputated limbs, a complete human burial and the remains of euthanised horses in one trench make the site at Mont-Saint-Jean truly unique.

“Finding horses, which had been put out of their misery by shots to the head, and humans buried alongside each other, especially with the care and separation evident in this trench, is extremely rare.”

Previous excavations by the charity across the Waterloo battlefield site, all of which have utilised the unique lived experience of veterans and serving personnel to help interpret their discoveries, have uncovered evidence that has rewritten the story of Waterloo; from an unrecorded attack on the field hospital to physical evidence of how the French nearly tipped the battle in their favour in the gardens of Hougoumont.

“Waterloo Uncovered supports veterans with their recovery and transition into civilian life. On site, veterans and serving beneficiaries will learn key transferable archaeological skills, which will provide pathways into education, employment, or simply enable them to enjoy archaeology as a hobby. Even professional archaeologists rarely get to work on a site of this calibre – it’s really a once-in-a-lifetime opportunity,” said Waterloo Uncovered’s CEO Abigail Boyle.

Anglo-Belgian landowner Anthony Martin, who runs a hugely popular brewery, brasserie, and museum at Mont-Saint-Jean farm (it produces a “Waterloo battle” beer) said, “Since we rescued the abandoned site of the Allied Field hospital in 2014, we have placed the farm’s fascinating heritage at the heart of everything we do. We are delighted to welcome Waterloo Uncovered back to Mont-Saint-Jean so that they can uncover even more of the site’s history while supporting modern-day veterans.”

The archaeology dig, the latest at the site, promises to be more exciting than ever, as Waterloo  Uncovered is returning to the site of its “biggest discovery” where it suspects it has only scratched the surface of what may be buried there.

This time it will be joined by a new cohort of British, American, Dutch and Belgian veterans and serving personnel, alongside its own archaeologists and volunteers.