Researchers headed by an archaeologist from Glasgow University believe they have unearthed evidence of a mass war grave dating back to World War I.
The team has spent more than two weeks examining the site
The site in Fromelles in northern France is thought to contain the bodies of 400 British and Australian soldiers.
Historians have long believed the grave existed after it was referred to in German war records from 1916.
The Battle of Fromelles was staged in an attempt to divert German troops away from the Battle of the Somme.
Dr Tony Pollard, director of Glasgow University's Centre for Battlefield Archaeology, described the find as being of "massive historical importance".
He spent two weeks surveying the area, using geophysics, radar, topographic surveys and metal detectors.
About 5,500 Australian troops were killed or injured in the battle along with 1,500 British soldiers - figures which were overshadowed at the time by the enormous loss of life at The Somme.
The battle is also noted as one in which future Nazi dictator Adolf Hitler fought against the Allies.
Dr Pollard hopes the discovery will focus new interest on the Battle of Fromelles.
He said: "The geophysics have proved the pits are there, and a metal detector survey has given very compelling evidence that Australian troops were buried there as there are metal artefacts such as medallions with Australian military insignia on them.
"That suggests beyond all reasonable doubt that the soldiers are there.
"There are only two explanations for this, either they were prisoners of war, which seems unlikely, or they were dead bodies.
"We believe the objects have fallen off the soldiers' uniforms as they were being manhandled in to the pits."
The search for the grave was commissioned by the Australian Government.
The country's war memorial in Canberra describes it as "the worst 24 hours in Australia's entire history".
Historian Peter Barton, who worked at the site alongside Dr Pollard, described the project as unique.
He said: "No mass grave like this has ever been found. The biggest found previously held only 20 or 30 people.
"We believe this is the biggest mass grave of the modern era that is not connected with genocide. It is quite extraordinary."
The death toll was overshadowed by carnage at The Somme
Allied dead from the battle were brought to the site on a trench railway and buried in the pits.
Dr Pollard said: "Hitler was in the 6th Bavarian reserve regiment that took part in the battle. He was 27 at the time and was acting as a runner in the battle.
"I'm not at all suggesting he was involved with the burial of these men, but he certainly took part in the battle."
The Australian Government is believed to be keen to conduct a full exhumation of the bodies, while a full report on the team's findings will be presented to the House of Lords War Graves and Battlefields Heritage group.
The archaeological team intends to carry out a small scale excavation of the site in the coming months.