How were bats used in during world war 2?

Actually, there was a brief program to use bats to deliver incendiary devices to buildings in Japan. First researched by the US Army in March 1943, it was turned over to the US Navy in August that year and was named Project X-Ray after several hundred bats with devices attached escaped the research facility and set fire to the the Auxiliary Army Air Base at Carlsbad, New Mexico and a lot of landscape surrounding it.

Small bats would be perched on racks that would be placed in bomb casings. When dropped from a plane, the casing opened and the bats scattered. The bats were to have small timed incendiary devices attached to them that would detonate and set fire to the buildings the bats perched in after dropped. both Army and Navy tests showed very high potential, but the program was scrapped after research into atomic weapons became more financially feasible.