The oldest archaeological evidence of chemical warfare was found in Syria (though the area was controlled by Rome in the third century). According to University of Leicester archaeologist Simon James, burnt bitumen and sulfur—which create toxic compounds when added to fire—killed about 20 Roman soldiers, whose bodies were found piled in a tunnel in the city of Dara-Europos, still holding their weapons."Chemical Warfare, From Rome to Syria. A Time Line."
At the time, explains James, an army from the Sasanian Persian Empire was attacking the Roman-controlled city, digging tunnels underneath its walls. Roman forces also started tunneling in order to counter the invaders—but the Sasanians had chemistry on their side. "I think the Sasanians placed braziers and bellows in their gallery," says James, "and when the Romans broke through, added the chemicals and pumped choking clouds into the Roman tunnel."
David Pescovitz is Boing Boing's co-editor/managing partner. He's also a research director at Institute for the Future. On Instagram, he's @pesco.