Answer: Bats

During World War II, the U.S. military developed a rather curious weapon: a bomb that unleashed incendiary bats. The premise, although worthy of a spy movie plot, was actually fairly simple. Bats like to roost in the eaves and attics of buildings, most Japanese buildings were very flammable, so why not release a bunch of bats with tiny incendiary bombs on their legs and then simply wait for them to roost?

As crazy as the plan seems, its development was actually successful due to several factors. First, bats are incredibly abundant (the caverns near the project’s original test site in New Mexico, alone, were home to millions of them). Second, bats are surprisingly strong and can fly while carrying more than their own body weight. Third, when in a hibernation state, you don’t have to feed or water them. And fourth, you can release them under the cover of darkness and they’ll automatically seek out their intended targets (places to roost) without any additional prompting or guidance.

Each bat carrier, or bat bomb, held 26 stacked trays each containing compartments for 40 bats. When dropped from a B-24 aircraft, each bat bomb would release 1,040 bats and those bats would in turn roost in buildings over a 20-40 mile distance from the drop site.

Although the project was promising, it was eventually canceled as it was taking too long to get field-ready and funds were diverted to nuclear projects. The creator of the project, Dr. Adams, however, maintained that the effort should have gone forward as widespread use of the incendiary bombs would have yielded the same, if not more, destruction as the atomic bomb without the devastating side effects and nuclear fallout.