Frightened Japanese Man: (pointing to the sky) "Aiii! Hi no komori!"
Never underestimate the potential absurdity of the military.
In 1942 the United States and the Empire of Japan were a little annoyed at one another and had taken to violently killing each other's citizens out of spite. Now there ain't no party like a World War party 'cause a World War party don't stop... unless you manage to destroy and/or terrify your opponent into submission. All sorts of incredible plans were cobbled together by both sides in order to bring about maximum destruction and/or terror; and some of them (let's face it) were just a tad goofy.
Project X-Ray was unlikely to ever win anyone a gold star, or even an A for Effort, but goddamned if it wasn't an actual, perfectly serious, "this seems like a good idea" Plan To Win The War.
At a basic level the plan was simply "burn entire Japanese cities to the ground", which seems to be a sound warlike solution to things. But the kicker here, see, was how all of this immolation was to be effected: suicide soldiers. Flying suicide soldiers. Very small, flying, suicide soldiers.
Bats, in fact. Specifically Tadaria braziliensis, the Mexican free-tailed bat, which was readily available for conscription in caves all over New Mexico and Texas.
Dr. Lytle S. (Doc) Adams, a dentist, had been visiting the caves near Carlsbad, New Mexico when the attack on Pearl Harbor occurred, and his recent experiences with the cave bats combined with his murderous hate for the dirty Japs to form a retaliatory plan of extreme ferocity. For most people the idle fantasy of burning Japan to the ground would remain the province of disturbingly satisfying dreams but Dr. Adams happened to be a partner of Tri-State Aviation, an airline which gave rides, gratis, to then-First Lady Eleanor Roosevelt. He whispered his scheme into her ear, she passed it along to her husband, who used the power of his office to order the U.S. Army to develop and ultimately implement Adams' idea. The U.S. Marine Corps was tasked with trapping as many bats as possible, and work began.
Doc Adams' Revenge was essentially this: millions of bats would be chilled into hibernation, fitted with small incendiary devices (either glued or tied to the bats), and loaded into canisters. The "bat bomb" would be released over the target area and slowed with a small parachute. At a given altitude, say 1000 feet, the cannister would burst open and release the bats. The bats would revive as they fell, take flight, and instinctually seek shelter in cave-like sanctuaries; hopefully the wood-and-paper houses and buildings of the target city. The incendiary charges would then detonate and simultaneously ignite thousands of raging fires all over Japan. A sure recipe for instant surrender (or, at the very least, mass death). Cost-benefit analysis projected that a planeload of bat-weaponry could start up to 4,800 individual fires, which was a significant "improvement" over the maximum 400 fires that traditional firebombing could cause.
Louis F. Fieser, the inventor of napalm, was hired to develop the actual munitions involved. He designed a small (19 gram) delayed-fuse charge to be attached to the bats' fur with glue. The fuse would activate when the bat bomb canister released the bats and had a delay time of approximately thirty minutes; enough time, it was surmised, for the bats to roost.
What could possibly go wrong?
There were a few setbacks. The original canister designs did not brake sufficiently before splitting open, and the bats' wings would be broken by the deceleration experienced when they tried to fly. But minor technological difficulties proved much easier to work around than the STUPENDOUSLY LARGE MISCALCULATION that was made when everyone involved forgot, in their zeal, that bats are wild animals which are unlikely to do anything you command them to do. Chalk that up to the military's underlying culture of absolute control. But, yes, the bats wouldn't behave.
During one live ammunition test, a large group of bats flew to a small town in Texas and roosted on a fuel tank which triggered the evacuation of the entire town and, I'm sure, a very tense re-trapping of the bats involved. A separate incident torched a general's car, and a few hangars and buildings at an airport in Muroc Lake, California. These were mere prologues to the comedy of errors played out when a whole flock of bats went "off target" and incinerated, almost totally, the new airbase at Carlsbad.
This was nearly the last straw for the Army who subsequently bequeathed the project to the Navy which abandoned it in 1944 after two full years of R&D and $2,000,000 (cheap!) in expenses (not counting destroyed property).
A slightly more feasible secret horror-weapon project overshadowed Project X-Ray and was used with some success on Hiroshima and Nagasaki the following year.
Sources: http://www.amnh.org/science/biodiversity/extinction/Day2/bytes/NovacekPres.html, http://www.news-journalonline.com/column/cshock/CULT053001.htm, http://www.thebulletin.org/issues/1993/m93/m93Bulletins.html, http://www.chiropteraphilia.com/cavehistory.html, http://home.nycap.rr.com/useless/batbombs/. There is also a book entitled Bat Bomb: World War II's Other Secret Weapon by Jack Couffer (one of the Project X-Ray design team) which I have not, as yet read, but is supposedly a highly entertaining read.