Despite sounding like something Batman would use, bat bombs were a very real thing that the army (and later navy) experimented with during World War II. They were the brainchild of Dr. Lytle S. Adams who was in Carlsbad Caverns when the war broke out, looked around him and said, "Well these tiny flying things look like they might be able to win the war." They weren't. But it's an interesting story anyway.
Some sources we consulted:
https://web.archive.org/web/20080531082803/http://www.afa.org/magazine/1990/1090bat.html
https://www.7dayadventurer.com/tag/dr-lytle-s-adams/
https://www.theatlantic.com/technology/archive/2011/04/old-weird-tech-the-bat-bombs-of-world-war-ii/237267/
https://en.wikipedia.org/wiki/Bat_bomb