A cramped tunnel beneath a Middle Eastern fort might have produced the oldest evidence of chemical warfare, according to a CSI-style review of archival records.
Presented at the recent meeting of the Archaeological Institute of America, the review focused on the dramatic remains of 20 Roman soldiers unearthed in the 1930s in the city of Dura-Europos, Syria.
Sitting on a cliff overlooking the Euphrates River, the Roman fort at Dura was the site of a violent siege by the powerful Persian Empire around 256 A.D.
No historical record of the battle exists, but archaeological remains have helped piece together the action.
The Persians used a range of siege techniques to enter the city. These included laying mines in tunnels underneath the walls to breach them. Intending to hold their ground at all costs, Roman defenders responded with counter-mines.
In the 1930s, archaeologists unearthed dramatic evidence of the fight: In one of the tunnels, a pile of bodies, still completely fitted with their weapons and armor, testified the horrors of the battle.
At the time, the researchers believed that the trapped Roman soldiers had died after the tunnel collapsed.
The reality was more gruesome, according to Simon James of the University of Leicester in England.
Mixing archival records and extensive fieldwork at the site, James was able to reconstruct the coldest of cold-case crime scenes, and came to the conclusion that the Roman soldiers had been deliberately stacked atop one another at the mouth of the countermine by the Persians.
"They used their victims to create a wall of bodies and shields, keeping Roman counterattack at bay while they set fire to the countermine, collapsing it," James said.
A question, however, remained: How did the Roman soldiers die? Killing almost two dozen fully armed men in a space less than 6 feet high and 36 feet long would have required "superhuman combat powers, or something more insidious," James concluded.
He noticed that previous reports described telltale mineral residues and yellow sulfur crystals in the tunnel.
"These provided the vital clue. When ignited, such materials give off dense clouds of choking gases," James said.
According to James, the Persians, who had heard the Romans tunneling, "prepared a nasty surprise." They placed fire pits strategically throughout the tunnel, and when the Romans broke through, the Persians gassed them by adding sulfur crystals and bitumen to the fire. This filled the tunnel with toxic sulfur dioxide gas.
James' "crime scene" also included the skeleton of a Persian soldier, lying alone.
"Probably, he is the man who set the fire. He lingered too long to ensure it was alight, and was himself overcome by fumes from the bitumen and sulfur he used to start the blaze," James told Discovery News.
According to Adrienne Mayor, a visiting scholar at Stanford University's Department of Classics and History of Science, most of the reconstruction of the underground battle mentioned in James' study "were already revealed by major excavations in 1920 to 1937 by teams from France and Yale University, and after 1986 by French-Syrian teams."
Mayor described the skirmish in the tunnel and the presence of burnt residue in her 2003 book "Greek Fire, Poison, Arrows and Scorpion Bombs."
"But James adds vivid new details, based on his careful analysis of the evidence. His real breakthrough is the remarkable fact that the Persian deliberately created a chemical weapon," Mayor told Discovery News.
The Persians failed to bring the walls down but somehow broke into the city. It was the end for Dura: Defenders and inhabitants were slaughtered or deported to Persia.