Animals have always been involved one way or another whenever there is human conflict— there were horses, elephants, and smaller ones like pigeons, dogs, rats. We’ve always come up with plans to weaponize them in ways that were never seen before. One unpopular experimental weapon developed by the United States of America during World War II was the use of bats to drop bombs over Japan.

The Concept

When Japan bombed the U.S. Pacific Fleet stationed at Pearl Harbor on December 7, 1941, it angered and woke up the nation’s men and women: many rushed to enlist and swore to make sure that the sun would never shine again to the land of the rising sun. One of them was a dental surgeon named Lytle S. Adams from Irwin, Pennsylvania, an acquaintance of First Lady Eleanor Roosevelt. He wrote a letter in January 1942 addressed to the White House, but this was not to enlist but to share his idea inspired by his recent trip to Carlsbad Caverns National Park in New Mexico. In a 1948 interview with the Bulletin of the National Speleological Society, Dr. Adams said:

“I had just been to Carlsbad Caverns, N. M., and had been tremendously impressed by the bat flight. . . . Couldn’t those millions of bats be fitted with incendiary bombs and dropped from planes? What could be more devastating than such a firebomb attack?”

In his letter, he wrote in detail about how they could strap tiny incendiary bombs to the bats, who would then carry the bombs into all the nooks and crannies of Japan. His letter was among the hundreds or thousands of letters that the White House received from people sharing their ideas on how they could pulverize Japan. Now bear in mind that most Japanese buildings were made of wood, bamboo, and paper at that time, so incendiary explosions could(and definitely did) cause a wild-spread fire. Perhaps it was because the idea was brilliant, or maybe it was that he personally knew the First Lady. But whichever it was, the idea went through a top-level scientific review with the Army Chemical Warfare Service (CWS) in conjunction with Army Air Forces. In the end, the idea was approved by President Roosevelt. The idea was set in motion and was, of course, led by Dr. Adams.

It’s important to note that Dr. Adams studied the idea before he proposed it by going back to Carlsbad to capture some bats that he could study. At home, he read and learned everything about these bats. How there are nearly 1,000 species of these flyers around the world, and each bat lives up to thirty years. He also found out that the free-tailed, or guano bat was the most common bat in North America. They were small and could catch up to 1,000 mosquitoes or gnat-sized insects in one night, a load that’s 12x their size. He also discovered that although they only weigh around nine grams, they can carry a load 3x their weight. These were all green lights to him.

Putting It To Action

On April 16, 1942, special-research assistant Donald R. Griffin sent a memo to the National Defense Research Committee (NDRC) of the National Inventors Council titled ‘Use of Bats as Vectors of Incendiary Bombs.’ There, he described Adam’s idea of using tons of bats carrying the incendiary time bombs that would be released at night over Japanese cities. The bats would find shelter in buildings or other installations, and when the time was up, these bombs would cause fires everywhere they took refuge.

With the help of a team of field naturalists from the Hancock Foundation, University of California, they set out to find where they could possibly get huge amounts of bats. They visited lots of caves and mines around the United States. In the end, they settled with the Mexican free-tailed bat because although they were smaller, they were the most populous at around twenty to thirty million, which they found and collected from Ney Cave.

In March 1943, the official authorization to begin with the experiment was issued from USAAF:

Subject: “Test of Method to Scatter Incendiaries.”

Purpose: “Determine the feasibility of using bats to carry small incendiary bombs into enemy targets.”

They closely studied these bats’ habits while also designing a small bomb that they could carry. It wasn’t that difficult for them at that time as they adopted England’s “baby incendiaries” used during WWI.

Attaching the Bombs

Two bombs were designed for the experiment. The first one weighed seventeen grams and would burn for four minutes with a ten-inch flame. The other was a bit heavier at twenty-eight grams and would burn six minutes with a twelve-inch flame. These bombs were oblong, nitrocellulose cases with thickened kerosene inside. On its side, a small time-delay igniter was made from a firing pin held in tension against a spring by a thin steel wire. A copper chloride solution would be injected into the cavity to corrode the wire to activate the bomb. Once the wire was corroded entirely, the firing pin would snap forward and strike the igniter head. The spark would then ignite the kerosene. They attached these to the bats by pinching away about one-half inch of loose skin from their chests and inserted a surgical clip and a piece of string. These bats were forced into hibernation by putting them in refrigerators.

Problems Encountered

Like any other experiment, Project X-ray encountered tons of problems, way too many.

The bats did not wake up from their cold-induced snooze right away and would plummet straight into the ground, still asleep (perhaps they could’ve tried an alarm clock first). There was also one time when some of the armed bats were accidentally released, leading to the burning of an airbase in New Mexico. The project was handed to the Marine Corps in August 1943, and they were the ones who called it “Project X-ray.” They did some more tests involving fake Japanese cities with some promising results. Regardless, the project was still canceled thirty demonstrations and $2 million later. The reason being was that they decided to focus on developing another secret weapon which was the atomic bomb— the outcome we already know about.

Dr. Adams was disappointed, but the bats were certainly relieved.