Thread by @Paracelsus1092

In AD 256 a unit of Roman miners led a counterattack against their Sasanian besiegers at the city of Dura-Europos.

What happened next has been recorded in minute detail by archaeologists, and remains amongst the earliest and most horrifying uses of chemical weapons in war 🧵

The fortified city of Dura-Europos on the Syrian Euphrates had been founded by the Seleucids. After falling to the Parthians and then the Romans in AD 165, it became an important outpost and border fort, somewhere between a town and a military garrison.

The Sasanian siege of AD 256 under Shapur I was part of their expansion and warfare against the Roman Empire, although no documentation of the siege has survived, if it ever existed.

For archaeologists the site has been referred to as the 'Pompeii of the desert', owing to the short Sasanian occupation period and the incredible preservation of military equipment and tactics used during the assault.

Three sides of the town were protected by river cliffs, but the western side had no such features. Instead a metre thick layer of very hard limestone capped softer gysum deposits, making trenches difficult to create but subterranean mines easy, once the limestone was broken.

The Romans shored up their defences by adding anti-ram features to the front of the western section, and building a large mud ramp on the inside.

The Sasanians attacked multiple points simultaneously, including the main gate, the southern desert wall with a large ramp and Tower 19. The use of mines and counter-mines became a defining feature of the struggle, with both sides using skilled engineers and tunnel technology.

Our story will focus on Tower 19, which was the target of a Sasanian mining and sapping operation, aimed at neutralising the tower as a projectiles platform and to collapse some of the wall for an infantry assault. The tunnels and spoil have been excavated since the 1920s.

The Roman counter-mine likely aimed to identify the Sasanian tunnel from above, and then quench any sapping fire by breaking through and extinguishing it with earth/soil, before a military pushback could be made through the Sasanian tunnel.

This height difference was probably identified by the Sasanians, and they prepared their own counter measures to ensure that, when the Roman mine broke through, they could be driven off.

The archaeology has been recently reinterpreted to support new evidence, in particular work on the skeletal remains discovered in the tunnels, and the careful stratigraphy of the internal fires and tunnel collapses. The story looks like this:

As the Sasanians heard the Roman tunnel above them and the sounds of digging downwards, they prepared a brazier of charcoals. As the ceiling started to crack open a single soldier lit the fire and added bitumen and sulfur crystals, his comrades retreating.

The upward draft engulfed the oncoming Romans who were plunged into an oily burning fury, the fumes of bitumen producing carbon monoxide and the sulfur forming acid in the eyes and lungs of the defenders. Choking and dying, they tried to exit in the dark, trampling and terrified

The lone Sasanian who started the blaze was also overcome and died in his armour. His friends may have used bellows or similar to help pump the smoke into the tunnels above and they waited for the noise and smoke to dissipate.

Once they were confident enough the Sasanians moved into the Roman tunnel, dragging the dead and dying men towards the entrance, where they propped them against the walls. This solves the puzzle of the unusual skeletal positions encountered by the archaeologists.

The Romans, some maybe still alive, were used as a blocking wall, while the attackers got on with their job of collapsing the wall above them, preparing a gallery packed with more sulfur and accelerants. A huge blaze destroyed the section of mine between the two sides.

This sequence of events would have been ghastly for all involved. Little air, almost total darkness, the confined space and terror of oily acidic smoke and fire combined into a vision of hell. The bravery of the men on both sides can be respected hundreds of years later.

Whilst the use of smoke generators is listed in older Greco-Roman military manuals, this might be the oldest evidence for chemical gassing in siege warfare. No doubt the Sasanians knew exactly what they were doing when they heaped up the sulfur and bitumen.

Most of the details and diagrams came from this paper.