How Were Bats Used in World War II?

The idea of using "bat bombs" against Japan in retaliation for the December 1941 sneak attack on Pearl Harbor may sound ludicrous, but, for a while, President Franklin D. Roosevelt was in favor of the plan, and American military experts worked on a prototype. The theory was that a bomb casing could contain thousands of hibernating bats, each trussed up with an incendiary device and a timer. If all went as planned, countless Mexican free-tailed bats would be released over Japanese cities, eventually roosting in eaves and attics and starting thousands of small fires.

An invasion of bat bombers:

• Lytle S. Adams, a Pennsylvania dentist who was an acquaintance of First Lady Eleanor Roosevelt, proposed the idea in January 1942 after a vacation to New Mexico, where he learned about bats in Carlsbad Caverns.
• The idea, later known as Project X-Ray, was seriously considered. Louis Fieser, the inventor of military napalm, designed small incendiary devices for the bats to carry.
• After numerous tests over several years, at a cost of about $2 million USD, it was determined that the bat bombs would not be ready until the middle of 1945. By that time, the atomic bomb was deemed to be a more expedient option in bringing about the end of the war.