Biological and chemical weapons have largely vanished from modern battlefields because they are incredibly hard to control and inflict horrendous suffering on their victims. Yet, as Machiavelli famously warned, “When it is absolutely a question of the safety of one’s country, there must be no consideration of just or unjust… one must follow to the utmost any plan that will save her life and keep her liberty.” This timeless advice underscores the brutal ingenuity behind the 10 historical biological attacks that have scarred the pages of warfare.
10 Historical Biological Attacks Overview
10 Siege Of Kirrha 590 BC
During the First Sacred War—also known as the Cirraean War—between the Amphictyonic League of Delphi and the Greek city of Kirrha, a surprisingly modern form of chemical warfare was unleashed. Kirrha’s relentless harassment of pilgrims heading to Delphi prompted the League to sabotage the city’s water supply by dumping the toxic plant hellebore into its wells.
Hellebore’s potent toxins trigger vertigo, swelling of the tongue and throat, a choking sensation, severe gastrointestinal distress, and can even cause cardiac arrest. The contamination caused massive bouts of diarrhea throughout Kirrha, leaving the defenders incapacitated and allowing the attackers to storm the city with little resistance.
9 Europos 256 BC
When Roman legions pressed against the walls of Dura‑Europos in modern Syria, the defending Sasanian troops resorted to a fiery concoction of bitumen ignited with sulfur, released through a tunnel the Romans were attempting to breach.
The resulting toxic fumes proved lethal, killing nineteen Roman soldiers in under two minutes. Archaeologists later uncovered sulfur crystals and the remains of the Roman soldiers, as well as a lone Sasanian whose hand may have set the deadly mixture alight.
8 63 BC
Mithridates VI, dubbed the “Poisoner King,” was infamous for self‑immunizing against a host of venoms. During the Third Mithridatic War, he equipped his archers with arrows dipped in snake venom; the tip would detach on impact, leaving a venom‑coated fragment in the wound that caused excruciating, days‑long agony before death.
He also scattered poisoned honey throughout the Georgian highlands, luring Roman troops to consume it. The honey induced vivid hallucinations and, in some cases, death. Though casualties were limited, the psychological impact rendered a sizable portion of the Roman force ineffective for nearly a week.
7 Siege Of Hatra 198
When Emperor Septimius Severus besieged the fortified city of Hatra, his troops employed a bizarre yet deadly weapon: terracotta pots packed with scorpions, wasps, and other stinging insects. As the Roman soldiers scaled the walls, the pots shattered, releasing swarms of venomous critters onto the battlefield.
The stings caused several fatalities, while many others suffered severe pain and illness exacerbated by the scorching sun. The chaos forced Severus to abandon the assault, leaving his forces humbled by the tiny but lethal arthropods.
6 Battle Of Tortona 1155
Holy Roman Emperor Frederick I, better known as Barbarossa, laid siege to Tortona during his Italian campaign. In a calculated move to weaken the city, he poisoned its wells, contaminating the water supply and precipitating a catastrophic famine.
The well‑poisoning coincided with a severe drought, rendering the already tainted water undrinkable. After allowing the civilian population to evacuate, Barbarossa set the city ablaze, sealing its ruin. Today, the town commemorates the siege each year with a reenactment that draws tourists from across the globe.
5 Battle Of Sandwich 1217
Facing an invading French fleet, English commander Baron William D’Albiney turned to a chemical surprise: quicklime (calcium oxide). He stocked the compound aboard his ships and, positioning his vessels upwind, unleashed a cloud of the caustic powder onto the French fleet.
The sudden blast blinded and irritated the French sailors, leaving them vulnerable to English boarding parties. The English seized the moment, overwhelming the French and capturing or killing almost all aboard, save for a few knights whose ransom proved lucrative.
4 Siege Of Kaffa 1346
During the 1346 siege of Kaffa, the Tatar forces of the Mongol Empire suffered a devastating outbreak of bubonic plague. Seizing the opportunity, they hurled the plague‑ridden corpses of their own fallen soldiers over the city walls, deliberately contaminating the defenders.
The biological onslaught forced the besieged to surrender to the Mongols. Some survivors fled Kaffa for ports such as Constantinople, inadvertently spreading the Black Death across the Mediterranean and into Europe.
3 Naples, Italy 1495
In the wars that ravaged southern Italy, Spanish troops employed a grim form of biological warfare: they mixed the blood of individuals afflicted with leprosy into bottles of wine sold to local Italians.
Leprosy, long viewed as a divine curse due to its disfiguring effects, spreads slowly and can remain dormant for five to twenty years. While this tactic did not cause immediate mass casualties, its psychological terror and long‑term stigma made it a particularly insidious weapon.
2 Siege Of Groningen 1672
During the Franco‑Dutch War, Bishop Christoph Bernhard van Galen of Münster turned to Atropa belladonna—deadly nightshade—to poison his artillery. Explosives and incendiary devices were laced with belladonna alkaloids, producing severe delirium, hallucinations, and even death among enemy troops.
The ghastly use of nightshade prompted the 1675 Strasbourg Agreement, the first international treaty banning “perfidious and odious” toxic weapons. This accord remained the sole prohibition of such devices until the 1925 Geneva Protocol expanded the ban to biological weapons.
1 Siege Of Fort Pitt 1763
In 1763, British forces entrenched at Fort Pitt in the Ohio Valley faced Native American opposition. To quell resistance, they distributed blankets contaminated with smallpox from a nearby infirmary to Native emissaries, hoping the disease would spread among the tribes.
General Amherst famously wrote, “Could it not be contrived to Send the Small Pox among those Disaffected Tribes of Indians? … Use Every Stratagem in our power to Reduce them.” The resulting epidemic devastated the Shawnee, Cherokee, Chickasaw, and Choctaw peoples, infecting thousands and dramatically weakening Native resistance.
+ Further Reading
If this list hasn’t left you both horrified and fascinated, dive deeper into the archives. Explore articles such as “10 Biochemical Attacks That Were Stopped Just In Time,” “10 Dark Facts About The Worst Chemical Terror Attack In History,” “10 Poisons And Their Horrifying Effects,” and “Top 10 Obsolete Weapons That Were Shockingly Deadly.”