Bat bombs were an experimental World War II weapon developed by the United States. The bomb consisted of a bomb-shaped casing with over a thousand compartments, each containing a hibernating Mexican free-tailed bat with a small, timed incendiary bomb attached. Dropped from a bomber at dawn, the casings would deploy a parachute in mid-flight and open to release the bats, which would then disperse and roost in eaves and attics in a . The incendiaries, which were set on timers, would then ignite and start fires in inaccessible places in the largely wood and paper constructions of the Japanese cities that were the weapon's intended target. The United States Navy took control in August 1943, using the code name ProjectX-Ray. Conception The bat bomb was conceived by Lytle S. Adams (1881-1970), a dental surgeon from Irwin, Pennsylvania who was an acquaintance of First Lady Eleanor Roosevelt. The inspiration for Adams' suggestion was a trip he took to Carlsbad Caverns National Park, which is home to many bats. Adams wrote about his idea of incendiary bats in a letter to the White House in January 1942—little more than a month after the attack on Pearl Harbor. Adams was intrigued by the strength of bats and knew that they roosted before dawn. He also knew that most of the buildings in Tokyo were constructed of wood instead of concrete. He believed that if time-release incendiaries could be attached to bats, some kind of container holding them could be dropped over the city after dark and the bats would simply roost and burn Tokyo to the ground. The plan was subsequently approved by President Roosevelt on the advice of Donald Griffin. In his letter, Adams stated that the bat was the "lowest form of animal life", and that, until now, "reasons for its creation have remained unexplained". He went on to espouse that bats were created "by God to await this hour to play their part in the scheme of free human existence, and to frustrate any attempt of those who dare desecrate our way of life." Of Adams, Roosevelt remarked, "This man is not a nut. It sounds like a perfectly wild idea but is worth looking into." After government approval After Roosevelt gave the project his approval, it was relegated to the authority of the United States Army Air Force. Adams assembled the workers for the project, including the mammalogist Jack