WWII Had a Secret 'Bat Bomb' Project!

During World War II, an intriguing and highly unusual concept for a weapon emerged from the mind of a Pennsylvania dental surgeon named Lytle S. Adams. Inspired by a trip to Carlsbad Caverns, where he witnessed millions of bats emerging at dusk (Review), Adams envisioned harnessing these creatures for the war effort. His idea, which he proposed to the White House in early 1942, was to equip bats with tiny incendiary devices and release them over Japanese cities, whose predominantly wood and paper structures made them highly vulnerable to fire.

The plan, codenamed "Project X-Ray," involved significant scientific and logistical challenges. Mexican free-tailed bats were chosen for their abundance and ability to carry a payload. Researchers developed small napalm bombs, weighing around 17 to 28 grams, designed with a delayed fuse. The bats were to be packed into bomb-shaped casings, chilled to induce hibernation, and then dropped from aircraft at a specific altitude. As the casings descended and warmed, the bats would awaken, disperse, and naturally seek out dark, secluded spots like attics and eaves within buildings to roost before dawn.

The project, which eventually transferred to the U.S. Navy and then the Marine Corps, saw extensive testing. One notable setback occurred when armed bats accidentally ignited a portion of the Carlsbad Army Airfield Auxiliary Air Base in New Mexico, burning down several facilities. Despite promising results in controlled tests, demonstrating that bat bombs could potentially cause far more fires than conventional incendiaries, the program faced delays and mounting costs, estimated at $2 million. Ultimately, the rapid development of the atomic bomb led to the cancellation of Project X-Ray in late 1944, as the military turned its focus to more immediately decisive weapons (Review).