The idea of biological warfare is not a modern construct. Take this quote, for example: “Fighting in a battle, he should not kill his enemies with weapons that are concealed, barbed, or smeared with poison.” So say the Laws of Manu, an ancient Brahmin text on moral conduct.

Man Is a Moral Animal

Our cultural evolution has spanned more than 2000 years of philosophy and theology. Darwin says in the Descent of Man that our moral sense is the highest product of human evolution. And yet, for all our grand philosophies, for all our lofty moral codes, we’ve warred against one another for centuries in the name of government, in the name of religion, or merely for the pursuit of plunder.

We are not the only animal to do so. Although coexistence often prevails, nature runs red with blood. Animals fight with horns, with hooves, with tooth and claw; they fight over territory; they fight over mates.

This is a transcript from the video series Mysteries of the Microscopic World. Watch it now, on The Great Courses Plus.

Even plants fight their own quiet battles, as do fungi and bacteria. But plants don’t have fangs, fungi don’t have claws, and microbes are sadly lacking in horns and hooves. Each one of them, however, can make exotic chemical compounds that will stop an enemy in its tracks. It’s no accident that many of our most powerful antibiotics have come from fungi and bacteria.

Biological Warfare in Historical Context

For centuries, primitive tribes in Amazonia have used poison dart frogs to coat their arrowheads with toxin. Homer describes the use of poisoned spears and arrows in his epic poems, speaking of “black blood,” which is commonly associated with snake bite and poisoned wounds.

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Hercules and the Hydra (ca. 1475) by Antonio del Pollaiuolo

Hercules started the ball rolling by dipping his arrows into the Hydra’s venom and using the poison arrows to slay the centaur, Nessus. And in the process, he learned an important lesson: Biological weapons often turn upon those who wield them. His wife was later tricked into smearing the venom on his cloak, and when Hercules donned the cloak he died a horrible and painful death. The Greek word for arrow poison, incidentally, is toxicon, which is derived from toxon (meaning bow or arrow). The Romans modified it to toxicum (meaning any kind of poison), from which we get the words “toxic” and “toxin.”

Hercules wasn’t the only Greek warrior to resort to poison arrows. The Oracle of Helenus told Odysseus that he had to recover the poison arrows of Hercules if the Greeks were going to defeat the Trojans. In the Odyssey, Homer says: “For there, too, went Odysseus in his swift ship in search of a deadly drug, that he might have herewith to smear his bronze-tipped arrows.” Like Hercules, the tables turned on Odysseus, who later dies from a poisoned spear.

Telegonus, the son of Odysseus and Circe, accidentally kills his father during a cattle raid using a spear tipped with a spine from a sting ray—the same deadly venom that recently killed the naturalist Steve Irwin.

Learn more about our overuse of drugs that were once a magic bullet against infection

Snakes and Scorpions Take to the Field of Battle

Hannibal

But the award for the all-time most imaginative use of natural toxin must certainly go to Hannibal. Remember the movie Snakes on a Plane? Hannibal, in A.D. 184, was fighting the naval forces of Eumenes II, king of Pergamum. Eumenes had a much larger fleet, and the outcome seemed really hopeless.

The Roman biographer Cornelius Nepos, in his Lives of Eminent Commanders, tells us that Hannibal ordered his troops to catch as many poisonous snakes as they could and stuff them into clay pots. In order to determine which vessel to attack, he sent a herald in a boat with a fake message for the king, filled with the vilest insults he could imagine.

Once Hannibal had identified his target from the king’s reaction, he ordered his ships to catapult the pots filled with snakes onto the deck of King Eumenes’s ship. Well, the enemy burst out laughing when they saw the clay pots come sailing through the air, but once the pots broke on the deck and the snakes came pouring out the laughter quickly turned to confusion and terror and Eumenes’s fleet beat a hasty retreat.

The Arabian city of Hatra, in the Second Parthian War around A.D. 198, repulsed a siege by the Roman legions of Emperor Septimius Severus by using the same trick, but substituting angry scorpions for the snakes. To the battered Romans, bombs filled with stinging insects and scorpions were probably the last straw.

The Romans themselves acquired a fondness for catapulting bee hives into the midst of their enemies. The historian John Ambrose, who is an expert on the use of insects in warfare, suggests that the decline in the number of bee hives in the late Roman Empire might be due to their frequent use as guided missiles.

Learn more about the different mechanisms that humans have evolved to defeat microbial invaders, and the strategies evolved by microbes to thwart those defenses

Early Germ Warfare

Centuries before we had any inkling of the existence of microscopic creatures, we were already using them in combat. The first known use of germ warfare was during the Anatolian War, around about 1320–1318 B.C., when the Hittites drove sheep and donkeys infected with tularemia into enemy territory. But the true masters of microbial mayhem were the Scythians. Herodotus tells us that the Scythians, in the 4th century B.C., coated their arrows with a home brew that must have been swarming with nasty microbes, including, we think, those that cause tetanus and gangrene.

They started by extracting the venom of freshly killed vipers, which were then set aside to decompose while they carefully separated the serum from human blood using a technique that’s been lost to human history. They mixed the blood serum with animal dung and buried the mixture underground in a leather pouch until it was sufficiently putrid.

The dung and serum mixture was then combined with the snake venom and the rotted snake tissue. It must have been incredibly potent, and the historian Strabo tells us that “Even people who are not wounded by the poison projectiles suffer from their terrible odor.”

The Romans and the Persians used to regularly poison their enemies by dumping dead animals into their wells. In 1155, the Holy Roman Emperor Barbarossa poisoned the wells of Tortona with the bodies of dead soldiers. The Turks came up with an interesting variation on this age-old scheme in 1346. The Crimean city of Caffa on the Black Sea (modern day Feodosiya) was then held by the Genoese. The Genoese had acquired it from the Mongols back in 1266, and they were using it as a base to dominate trade in the Black Sea.

Weaponizing the Plague

The Genoese and the Mongols didn’t always get along. In 1343, Jani Beg, the new Kahn of the Golden Horde, attacked Caffa with his Turkish mercenaries. After 3 years of siege, the Turks were completely fed up and suffering from plague, so they decided to use their own infected dead as weapons. They used catapults to launch the dead plague corpses into the city, until the defenders sickened and died.

The contemporary historian Gabriele de’ Mussi tells us:

What seemed like mountains of dead were thrown into the city, and the Christians could not hide or flee or escape from them, although they dumped as many of the bodies as they could in the sea. And soon the rotting corpses tainted the air and poisoned the water supply. … Moreover one infected man could carry the poison to others, and infect people and places with the disease by look alone.

The Genoese scattered to ports all across the Mediterranean, spreading the Black Death to Europe, and igniting a series of pandemics that would devastate the European population. The Tunisians, in 1785, flung infected clothing rather than corpses into the besieged city of La Calle. The British used a similar strategy against native tribes in colonial America, giving them blankets that were infected with smallpox.

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The very first use of biological warfare in the New World, however, may have been by the Indians against the British. The French historian Pierre-François-Xavier de Charlevoix writes of a band of Iroquois in the early 1700s who poisoned a stream used by English troops. They threw all of their recently skinned animal pelts into the stream, and succeeded in killing over 1000 British soldiers who later drank the tainted water.

Microbes Don’t Choose Sides

These crude tactics of our ancestors pale before our modern-day ability to cultivate the deadliest microbes on the planet. But before the discovery of antibiotics, there was no way to prevent the microbe from turning on any army that released it. Any microbe on the battlefield would kill without regard to national identity. In World War I, gas was the preferred weapon, although fickle winds would sometimes turn it back on those who used it, as well.

Gas attacks by the Germans in World War I cost 91,000 Allied casualties, and an unknown number of German casualties from allied counterattacks. The use of chlorine gas, phosgene, nerve gas, and mustard gas killed or maimed millions of soldiers and civilians. One of the victims of the Allied gas attacks was a young German corporal by the name of Adolph Hitler. Hitler was temporarily blinded by an Allied mustard gas attack on the Belgian village of Warwick, during the closing days of the war. This may explain why the otherwise ruthless dictator was hesitant to use biological or chemical weapons during World War II.

Learn more about the history of microbes as weapons, predating the practice of catapulting disease-infected corpses into enemy strongholds

In the second article in this series on biological warfare, we look at the laws set forth against the use of biological weapons during the Geneva Protocol of 1925. Read it here.

Common Questions About Biological Warfare