Ancient Persians were the first in the world to have used chemical weapons to defeat their opponents, scientists said, cited by the BBC.
British archaeologist Simon James from the City University of Leicester has found that even in the third century AD, an army of the Persian Empire had used poisonous gas during the siege of the ancient Roman town Dura, located in eastern Syria.
His theory is based on a survey of the remains of 20 Roman soldiers, found near the foundations of the city walls.
According to the theory of James, Persians dug a tunnel under the castle wall and set fire to the bitumen and sulfur crystals, resulting in what has been dense poison gas.
After a few seconds, the Romans lost consciousness and later died in minutes.
Persians gathered the bodies of the deceased Roman soldiers and placed one over another, thereby creating a protective barricade, after which they set fire to the tunnel.
"The results of archaeological excavations in Dura is evidence that the Persians were not ill-prepared by the Romans in the art of siege and have used the most brutal methods, "says James.