Throughout recorded history, humans have excelled when it comes to finding new and inventive ways to kill each other. War really kicks that knack into overdrive, so it seems natural that humans would turn to the animal kingdom to supplement their arsenals. The Assyrians and Babylonians were among the first to utilize war dogs, but they were far from the last. During World War II, the Soviets took things to another level, turning man’s best friend into a furry anti-tank mine. The Persian king Cambyses II is said to have driven cats—an animal sacred to his opponents, the Egyptians—before his army at the Battle of Pelusium in 525 BCE. And horses played a pivotal role in warfare until the first half of the 20th century. But domesticated animals are easy. If one really wants to stand out in the crowded field of militarized fauna, you need to get a bit exotic.
Hannibal famously used elephant cavalry during his invasion of Italy during the Second Punic War, taking dozens of the animals with him as he transited the Alps. As terrifying as the ancient armored vehicles were, the Romans soon adopted responses to them (simply stepping aside and allowing them to pass through the massed Roman ranks was an effective technique). In the end, Hannibal ran out of elephants long before the Romans ran out of Romans.
In the 1960s, these savvy cetaceans were enlisted by the U.S. and the Soviet Union as part of the Cold War arms race. Trained by the navies of both countries to detect mines and enemy divers, “battle dolphins” remained in use into the 21st century. When Russia occupied and annexed the Ukrainian autonomous republic of Crimea in March 2014, included among the spoils was the Ukrainian navy’s military dolphin program.
Historically, rats have been rather unwelcome, if largely inescapable, companions for the world’s militaries. They destroyed provisions aboard navy ships, they spread disease among camps, and they fed on the corpses of the unburied dead. During World War I, trench rats were such a pervasive nuisance that commanders had to adopt rules against shooting the creatures, for fear of depleting stocks of ammunition. In the 21st century, however, rats have been trained to comb former battlefields in search of land mines. These deadly remnants of war claim hundreds of lives each year, and the rats’ powerful sense of smell allows them to uncover even those mines that avoid electronic detection.
Perhaps because a Planet of the Apes scenario has always seemed just a bit too plausible, humans have not tried to weaponize other primates on any serious scale. Giving a sword or rifle to an animal with near-human intelligence and vastly superior strength just seems like a bad idea all around. Chimps did, however, play a prominent role in the space race. While the Soviet Union conducted what amounted to an orbital canine euthanasia program, the United States paved the way for the Mercury astronauts with Ham, a chimp who achieved suborbital flight and became something of a mascot for the U.S. space program. Ham died in 1983, after spending the remainder of his life in captivity, and his partial remains are interred at the New Mexico Museum of Space History in Alamogordo, New Mexico. Other “astrochimps” met rather worse fates, being leased to medical research laboratories after the U.S.A.F. concluded its space chimp program in the 1970s.
Often disparaged as “rats with wings,” the humble pigeon has acted as a battlefield messenger since at least Caesar’s conquest of Gaul in the first century BCE. On the Western Front, where things were often too quiet due to the vulnerability of telegraph cables and human runners, pigeons were used to carry vital messages to and from the battle lines. The homing pigeon Cher Ami saved the lives of nearly 200 American soldiers by delivering the message that a misdirected artillery barrage was falling on friendly troops. During World War II, the British intelligence service MI5 recognized the potential for clandestine communication conducted via pigeon (Nazi SS chief Heinrich Himmler was, in fact, the President of the German National Pigeon Society), and it enlisted a team of falconers to patrol the British skies. According to the declassified after action report, the falcons failed to bring down a single enemy pigeon, but two pigeons were captured and made “prisoners of war.”
When an individual is regarded as one of the greatest military leaders in history, he’s bound to show up on a list like this more than once. With that, we return to Hannibal, beaten by the Romans, driven from his native Carthage, and forced to seek refuge with King Prusias of Bithynia. Still determined to strike at Rome in any manner possible, he counseled Prusias in his conflict with Eumenes II, leader of the Roman client state of Pergamum. The Bithynians lacked the manpower to triumph on land, so Hannibal took the battle to the sea. The situation there wasn’t much better, but Hannibal was a master of working with the tools at hand. And the tools that he had were snakes. Lots and lots of snakes. He ordered his men to gather them up and place them in earthen pots. Then, Hannibal did the only logical thing that one could do when presented with a giant pile of snake-filled jars—he rained them on the enemy flagship with catapults. Biological warfare is generally conducted with organisms that aren’t visible to the naked eye, but Hannibal was not a man of small gestures. The resulting “snakes on a boat” scenario played out predictably, and the Bithynians were victorious.