Scientists have discovered an unexpected "ally" for Russia in the war against Napoleon.

Scientists analyzed DNA from the dental remains of 13 soldiers discovered in a mass grave in Vilnius in 2001.

"The tests confirmed that each of the bodies was infected with Borrelia recurrentis and Salmonella enterica paratyphi C," the publication says.

Historians, ABC writes, long believed that most of Napoleon's retreating army was decimated by typhus and trench fever. However, there was no reliable evidence to support this. Recent research has shown that these bacteria were the culprit.