During WWII, the US planned to drop 1000s of bats with tiny bombs on Japan
Imagine: a quiet, tense night in the middle of wartime. A plane rips through the air above your city, rupturing the stillness. The bay doors open, and out whistles a bomb. It drops and drops. Everyone braces. But when it explodes, the city is filled not with the flash of impact, but with hundreds and hundreds of tiny, whirling bats.
This ridiculous vision—in which Japanese cities were destroyed by a giant bomb full of bats that were themselves carrying tinier bombs—was called Project X-Ray, and it was but a claw's breadth from becoming a reality.
A canister to hold 1000 bats with their tiny bombs
It took a dentist to come up with such a nightmarish plan. Like many Americans, Dr. Lytle S. Adams was incensed by the Japanese attack on Pearl Harbor, enough to turn his mind towards the war effort. Adams had just returned to his Pennsylvania home from a vacation in New Mexico, where, he remembered years later, he had been “tremendously impressed” by the Mexican Free-Tailed Bats that migrate through the state and roost by the millions in Carlsbad Caverns.
A bat with his tiny bomb
Adams read up on bats. He returned to Carlsbad Caverns and captured some of his own (it was a different time). Through study and observation, he realized that the little critters are war machines, perfectly calibrated for withstanding high altitudes, flying long distances, and carrying heavy loads—for example, timed bombs.
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Much more: http://www.atlasobscura.com/articles/the-almost-perfect-world-war-ii-plot-to-bomb-japan-with-bats
Thankfully this plan got nixed. They thought enough of it to actually carry out tests though.
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Why do dentists hate animals so much?! 
They burned down the whole test range, when only one building had been intended.
Interesting to see that both Louis Fieser and Bing Crosby played a role in this project.
