A UK researcher said he found evidence that the Persian Empire used poisonous gases on the Roman city of Dura, Eastern Syria, in the 3rd Century AD.
The theory is based on the discovery of remains of about 20 Roman soldiers found at the base of the city wall.
The theory is plausible enough, though it is a little over sold. In any case, the historical evidence is clear that it sucked to be Roman soldier trying to stop the Persian invasion.