An engraving of ancient Roman equestrian soldiers by Julius Romanus

The prospect of chemical and biological warfare in this age of anthrax scares and WMD can feel  like the threat of nuclear Armageddon before it  like a uniquely modern terror. But a British archaeologist's recent find offers a reminder that chemical weapons are nothing new  in fact, they are nearly 2,000 years old. Simon James, a researcher at the University of Leicester in the U.K., claims to have found the first physical evidence of chemical weaponry, dating from a battle fought in A.D. 256 at an ancient Roman fortress. James concluded that 20 Roman soldiers unearthed beneath the town's ramparts did not die of war wounds, as previous archaeologists had assumed, but from poison gas.

The findings, announced in January at a meeting of the Archaeological Institute of America in Philadelphia, have caused a stir in archaeological circles, bringing to light proof of deeds usually encountered just in classical texts. Conducting a CSI-style cold-case forensic analysis of the site, James pieced together clues from records of earlier excavations at the Roman city of Dura-Europos, whose ruins are in modern Syria. An army of Persians had sacked the city and abandoned it, deporting its captive population deep into Persian territory. Dura-Europos became a ghost town, engulfed in sand until joint French-American teams dug it up in the 1930s. (Read TIME's cover story on a different kind of modern U.S. military weapon.)

During the final siege of the city, the attackers burrowed beneath the walls in order to breach the Roman defenses; the Romans heard this and started digging a countermine to fend off the assault. But the Persians, James told TIME, "prepared a nasty surprise," pumping lethal fumes from a brazier burning sulfur crystals and bitumen, a tarlike substance, with bellows into the Roman tunnels. The brazier was only doused, James suggests, "when the screaming stopped." Afterward, the Persians stacked the Roman corpses in a wall to prevent any reprisal, then lit the scene on fire.

War in antiquity rarely matched the heroism of its myths  it was ugly, nasty and desperate. To stave off a Roman siege in A.D. 189, the defenders of the Greek city of Ambracia built a complex flamethrower that coughed out smoking chicken feathers. At Themiscrya, another stubborn Greek outpost, Romans tunneling beneath the city contended with not only a charge of wild beasts but also a barrage of hives swarming with bees  a rather direct approach to biological warfare.

The Romans themselves had few qualms about incorporating chemical warfare into their tactics. Roman armies routinely poisoned the wells of cities they were besieging, particularly when campaigning in western Asia. According to the historian Plutarch, the Roman general Sertorius in 80 B.C. had his troops pile mounds of gypsum powder by the hillside hideaways of Spanish rebels. When kicked up by a strong northerly wind, the dust became a severe irritant, smoking the insurgents out of their caves. The use of such special agents "was very tempting," says Adrienne Mayor, a classical folklorist and author of Greek Fire, Poison Arrows & Scorpion Bombs: Biological & Chemical Warfare in the Ancient World, "especially when you don't consider the enemy fully human."

Unconventional methods were used by both antiquity's weak and strong. In 332 B.C., the citizens of the doomed port of Tyre catapulted basins of burning sand at Alexander the Great's advancing army. Falling from the sky, the sand, says Mayor, "would have had the same ghastly effect as white phosphorus," the chemical agent allegedly used during Israel's recent bombardment of Gaza, not far to the south of ancient Tyre. A Chinese ruler in A.D. 178 put down a peasant revolt by encircling the rebels with chariots heaped with limestone powder. Accompanied by a cacophonous troupe of drummers, the charioteers pumped the powder into a primitive tear gas even more corrosive and lethal than its modern equivalent. The peasants didn't stand a chance. (Read "Could Israel Face War Crimes Charges Over Gaza?")

Still, in the absence of the Geneva Conventions, ancient peoples did maintain "some sense of what it was to cross the line," says Mayor. Across cultures, it was customary to deplore trickery and extol the virtues of the noble warrior. The Brahmanic Laws of Manu, a code of Hindu principles first articulated in the fifth century B.C., forbade the use of arrows tipped with fire or poison. Written in India a century later, Kautilya's Arthashastra, one of the world's earliest treatises on war and realpolitik, advocates surprise night raids and offers recipes for plague-generating toxins, but it also urges princes to exercise restraint and win the hearts and minds of their foes. The Roman military historian Florus denounced a commander for sabotaging an enemy's water supply, saying the act "violated the laws of heaven and the practice of our forefathers."

Even in antiquity, many feared the lurking consequences of unleashing what we now call chemical weapons  indeed, the ancient Greek tale of Pandora's box offers a continuing metaphor for their use. And its moral proved true in the collapsed tunnels of Dura-Europos: among the Roman bodies, James spied one corpse set aside from the rest, which wore differing armor and carried a jade-hilted sword. This was a fallen Persian soldier, James concludes, also asphyxiated by the gas. The warrior who released the poison very likely succumbed to it.

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