Giant 5,000-Mile Balloon Bombs: Japan’s Silent Attack on North America

In the waning months of 1944, a peculiar series of events began to unfold over the skies of North America. Residents and military personnel alike reported seeing strange objects floating in the sky, sometimes accompanied by a soft whistling noise followed by unexpected explosions. Initially, there was widespread confusion amongst local government officials and the military, with some believing that the German Air Force might be infiltrating U.S. airspace to parachute bombs onto targets. The targets seemed random, primarily forested areas with no clear strategic value.

The Emergence of Balloon Bombs during World War II

It was only when an undamaged specimen of these mysterious objects was recovered that the true picture emerged. The U.S. military realized they were dealing with a new kind of threat—unmanned balloon bombs launched from Japan. They were silent attackers floating across the ocean to American soil. U.S. officials, taken aback by this discovery, implored the media to keep a tight lid on the situation, fearing that public knowledge might lead to panic or expose the vulnerability of American airspace.

These balloon bombs were a product of harsh wartime conditions for Japan. After the American Doolittle Raid on Tokyo in April 1942, which shook the Japanese people’s sense of security despite causing minimal physical damage, Japan’s military strategists were desperate to strike back. This led them to resurrect a nearly forgotten idea: attacking an enemy with balloon-borne weapons.

The Japanese Imperial Navy charged Technical Lieutenant Commander Kiyoshi Tanaka with creating a suitable balloon device for this purpose. Despite resource shortages, he succeeded in designing an impressive 29.5-foot diameter balloon constructed from rubber-coated silk, a material choice that balanced the need for flexibility and durability. Although this rubber balloon design was used for preliminary data collection rather than offensive operations, the more commonly deployed paper balloons—measuring 32.8 feet in diameter—were designed to deliver actual payloads.

Development and Deployment of Japanese Balloon Bombs in WWII

In contrast, the Japanese Imperial Army’s paper balloons were made with a much cheaper material. They utilized a pasting technique involving an adhesive derived from arum roots and a lacquer made from fermented persimmons to waterproof their exterior. The paper balloons bore the true menace; each one carried incendiary devices and a cluster bomb meant to detonate upon reaching North American land, sowing destruction and fear.

Not new to balloon technology, Japanese forces had contemplated employing balloons to deliver propaganda leaflets during their conflict in Manchuria in the 1930s. In the context of WWII, Japanese meteorological intelligence revealed the existence of an eastward-flowing jet stream at high altitudes over the Pacific Ocean. This discovery was integral to delivering the bombs, allowing them to ride the winds from Japan to North America in as little as 30 to 60 hours depending on atmospheric conditions.

Dubbed Project Fugo, the initiative aimed primarily to ignite catastrophic forest fires in the Pacific Northwest, diverting U.S. resources and stirring unease among the American populace. The concept was straightforward yet bold: use balloon bombs to strike silently and unpredictably within the United States. However, Project Fugo had a significant flaw: the balloons’ flight paths were at the mercy of varying jet streams, making it impossible to predict their arrival times or exact landing zones.

Impact and Response to Japanese Balloon Bomb Attacks in WWII

Despite these limitations, the balloons began to wreak silent havoc. On November 3, 1944, a rubber balloon with a radio transmitter landed near San Pedro, California. Then, on December 6, near Thermopolis, Wyoming, the first explosion attributed to these balloon bombs occurred. Following this, a paper balloon bomb carrying an incendiary device was discovered near Kalispell, Montana, and shortly after, another balloon caused a power outage in Washington state, affecting a critical plutonium-producing facility.

Even after the war’s conclusion, balloon bombs continued to appear sporadically across North America. Persistent discoveries over the years, with some even as recent as 2014, painted a picture of how widespread the balloon bomb campaign had been. This unusual threat from across the Pacific prompted a coordinated U.S. response. With federal agencies, and the military involved, efforts were made to recover the devices for analysis and to safeguard against potential biological attacks—a concern of the FBI, although Japan never employed such methods. In response to this aerial enigma, the U.S. increased patrols along the coast and placed firefighting troops on standby. However, the blackout of news on the matter proved to be a pivotal aspect of the national defensive strategy.

The Japanese military, largely unaware of the effectiveness of their balloon bombs and misled by exaggerated or fabricated success stories in their own propaganda, eventually dismissed the effort. The program tapered off in early May 1945, possibly due to American air raids disrupting manufacturing processes or disrupting the delivery of crucial materials.

Once a strategic whisper in the winds of war, over 6,000 balloon bombs marked Japan’s silent attempt to shift the scales in a global conflict; an audacious and overlooked chapter in the annals of World War II history.