During my last episode about sonic tactics, I talked about the different audio strategies that animals have developed for hunting prey and escaping predators, whether they're orcas using tail slaps to stun schools of fish or moths evading a bat's sonar with their clicks. As it turns out, some of those strategies are surprisingly similar to the sound tactics we've been using on the battlefield for centuries. This week I'll be delving deeper into how those same sonic strategies have played an important role throughout the history of war, from ancient Roman war pigs to inflatable army tanks.Since animals already rely so much on sound to survive, it may be no surprise that one of the first uses of sound as a battle plan was to try and scare off the other side’s animals. Perhaps the most fearsome mount ever faced in antiquity was the war elephant: they were the tanks of the ancient world, massive and nearly unstoppable during a charge. But elephants are skittish, and it didn’t take long for their enemies to stumble upon a sound that would send even the bravest pachyderm running: the squeal of a pig. “War pigs,” as they came to be called, were sent stampeding among the approaching war elephants to make them panic and trample their own riders. To counter this gambit, elephant trainers began to raise pigs alongside their war elephants so they’d grow accustomed to the sound.The idea of using sound to evoke fear among the enemy isn't limited to animals. One of the most distinctive sounds on the battlefields of ancient Japan is the kabura-ya (kah-burr-ah-yah) arrow, which literally translates as "turnip arrow." They're often called whistling arrows because, thanks to their hollow, turnip-shaped heads, that's just what they did. The sound of a kabura-ya flying through the air was believed to dispel evil influences, and they were used as signals to announce each army's arrival on a battlefield. While their use by samurai started to fade after the twelfth century, such arrows were also used by bandits to signal their approach all the way through the twentieth century.Want to hear what one sounds like? There’s a video link on my blog so you can listen and imagine that ghostly whistle just before a battle, or while walking alone in a forest:https://www.youtube.com/watch?v=maMnRvJVih8While the sound of a kabura-ya arrow relayed honest, if unsettling, information about an approaching army or nearby bandits, wartime audio strategies often involved using sound to confuse the listeners. Just as some animals use sonic camouflage to disguise themselves, ancient armies learned to use sound to conceal their numbers and deceive their enemies. One of the oldest and most famous accounts of audio misdirection is the Biblical story of Gideon, who, around three thousand years ago, used horns, torches, and a scattered group of three hundred soldiers under the cover of darkness to trick an enemy camp into thinking they were under attack by a massive army and retreating.That’s a strategy we’re still using today, even as we’ve replaced horns and torches with speakers and spotlights. During World War II, a top-secret group of American soldiers officially known as the 23rd Headquarters Special Troops arrived in Europe. They were nicknamed the “Ghost Army,” and their ranks included artists, architects, actors, and other creative professionals who could think on their feet. Their goal was to trick the German army into thinking their thousand-man unit was, in fact, an army of more than 30,000 soldiers, and draw their attention away from the Allies’ actual targets.The Ghost Army did this by using inflatable prop tanks, trucks, and airplanes, by faking radio messages for the Germans to intercept, and through the use of sound in ways that never would've been possible before the twentieth century. They drove sound trucks equipped with massive amplifiers that could play and mix separate sound effect recordings to...