The United States has always had its own advanced weapons systems research division and among the most advanced systems ever developed during WWII was the Bat Bomb.
In January 1942 dental surgeon Lytle S. Adams was given a go ahead for the project. Believe it or not, here is how it was supposed to work: The bomb was comprised of 26 flat chambers, each that carried 40 Mexican Free-Tailed Bats. Each bat had an incendiary explosive attached that was timed to go off a few hours later. A bomber would drop the bomb from 5000 feet at sunrise and a chute would open the chambers at around 1000 feet. The bats would scatter around looking for eaves and gutters and barns to settle in for the day.
The resulting fires would be widespread and rather unexpected. Tests showed that it worked, but it was never used on Japan.
Sources and Citations
Bat Bomb: World War II’s Other Secret Weapon, by Jack Couffer, University of Texas Press, 1992.