The US Army Air Forces hoped that bats could be outfitted with tiny explosive harnesses, then dropped over Japanese cities—starting hundreds of small fires that would spread out of control.

As the tide turned in its favor in the Pacific during World War II, the United States came within striking distance of Japan—and the US Army Air Forces (USAAF) began to earnestly consider how they could bomb Japan in ways that would hurt the country’s industrial production and civilian morale without risking significant US casualties. The idea of the bombing campaign was to stop Japan’s war machine and weaken public support for the war, making a surrender more likely.

The bombing campaign, of course, culminated in the dropping of two atomic bombs on the cities of Hiroshima and Nagasaki in August 1945. However, before those bombs were completed, the United States was quite serious about another, more primitive one: this one involving thousands of live bats. Known as Project X-Ray, the idea was simple, if bizarre: strapping tiny incendiary bombs to bats, then releasing them over a Japanese city to burn it down.

About the “Project X-Ray” Bat Bomb Plan

The concept of a “bat bomb” sounds outlandish, like something from a cartoon (or a campy 1960s television show). But it was a real proposal based on demonstrated animal behavior and the material composition of Japanese towns, and if actually executed, it might have led to devastation.

Under the plan, time-delay incendiary bombs would have been strapped to small bats, which would have then been packed into bomb-shaped containers loaded onto US bombers. Instead of conventional ordnance, the bombers would have dropped the bat canisters over a target in Japan. The canisters would break open in midair, causing the bats to awaken and disperse.

The bats would then roost beneath roofs and inside buildings. After a delay of several hours, the incendiary bombs would ignite at the same time, causing thousands of small fires to break out across a city and making it impossible for a local fire department to confront them. 

The bat bomb idea was first put forward by Lytle S. Adams, a Pennsylvania dentist and inventor. After he visited Carlsbad Caverns, famous for its enormous bat population, and after the Japanese attack on Pearl Harbor, Adams conceived of the bat bomb idea. Arguably, Adams’ central insight wasn’t so much about bats but rather about Japanese construction, which relied heavily on wood, paper, and bamboo—all extremely combustible.

Adams reasoned that bats could deliver incendiaries into thousands of inaccessible locations simultaneously. He sent the proposal to the White House in January 1942, one month after the Pearl Harbor attacks. Remarkably, the proposal got through to President Franklin D. Roosevelt, who ordered the military to investigate.

American researchers considered different species before ultimately settling on the Mexican free-tailed bat. These bats offered several useful characteristics, including small size, the ability to carry comparatively substantial loads relative to their body weight, the tendency to seek dark and protected roosting spaces that Japanese firefighters would have trouble reaching, and the availability of enormous populations throughout the American Southwest. Importantly, the bats could be manipulated in ways that made it easier for them to handle: they would begin to hibernate if put in cold temperatures. The protocol that the USAAF ultimately settled on included cooling the bats into a torpor and attaching the incendiaries before packing them into the canister.

Chemist Louis Fieser, who was later associated with the development of napalm, worked on the miniature incendiary device, which weighed only a few ounces. Using napalm-like incendiary material and delayed ignition mechanisms, the mechanism could start a sustainable fire within a fairly precise timeframe; once ignited, it was hoped that combustible materials in the bat’s roosting space would fuel the further spread of flames.

Unlike Many Crazy Military Ideas, Project X-Ray Was Proven to Work

The idea remained outlandish, and the USAAF approached it during late 1942 and early 1943 with some skepticism. Ironically, an accidentally successful test nearly resulted in its cancellation; in May 1943, a group of released bats took refuge under a fuel tank at the Carlsbad Army Airfield, destroying it. After that incident, the project was transferred to the US Navy in August 1943, then to the Marine Corps. 

At the Dugway Proving Ground in Utah, the US government had built a mock-up of a Japanese town, using construction types commonly found in Japan. The Marines began testing the bats and the incinerator mechanism in the summer of 1943, with promising results; the sample village was destroyed in the tests.

Despite its destructive potential, the project ran into obstacles. Its primary problem was that it was far more logistically complicated than a conventional pallet of firebombs—requiring thousands of live bats to be collected, then transported on ice across the Pacific, then outfitted with tiny explosive harnesses. By 1944, its combat readiness remained too far away for use, and the program was quietly shelved.

Ultimately, the US government spent around $2 million (around $38 million today) on Project X-Ray. And not all of the money was wasted. Throughout it, American scientists considered the composition of Japanese cities, and came to realize their vulnerability to fire. Though bombers ultimately delivered conventional incendiary bombs rather than bats, the firebombing concept was vindicated in March 1945, when USAAF Gen. Curtis LeMay carried out a catastrophic air raid against Tokyo, incinerating much of the city and killing an estimated 100,000 people.

Project X-Ray remains one of the stranger anecdotes in modern weapon development history. But the project was viable, potent, and incredibly creative.

About the Author: Harrison Kass

Harrison Kass is a writer and attorney focused on national security, technology, and political culture. His work has appeared in Tablet, City Journal, The Hill, The Spectator, and The Cipher Brief. He holds a JD from the University of Oregon and a master’s in Global & Joint Program Studies from NYU. More at harrisonkass.com.

The post How the United States Planned to Use Bats as Bombs During World War II appeared first on The National Interest.