The siege was notable for the early
use of chemical weapons by the attacking Persian army. During the siege the attackers dug several underground shaft mines under the city walls. The Romans dug tunnels to reach the mines and fight the diggers underground. In one such tunnel, when the Romans broke through into the Sasanian tunnel the tunnelers ignited a mixture of
sulfur and
pitch, producing a cloud of
sulfur dioxide, which killed twenty Roman soldiers, one of which was carrying a coin dated 256, allowing the dating of the siege. Archaeologists excavated the scene in the 1930s. In 2009 tests showed the presence of sulfur dioxide inside the tunnel. In 2020, a group of chemistry students in
Foxborough, Massachusetts used chemical analysis of the samples in the tunnel compared with the composition of
bitumen and deduced that methane was also likely a by-product of the attack. ==Gallery==