was an deployed by Japan against the United States during World War II. A

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxi ...

balloon measuring in diameter, it carried a payload of two incendiary devices plus one anti-personnel bomb (or alternatively one

incendiary bomb Incendiary weapons, incendiary devices, incendiary munitions, or incendiary bombs are weapons designed to start fires or destroy sensitive equipment using fire (and sometimes used as anti-personnel weaponry), that use materials such as napalm, ...

), and was intended to start large forest fires in the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

. Between November 1944 and April 1945, the Japanese launched about 9,300 balloons from sites on

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separat ...

, of which about 300 were found or observed in the U.S., with some in Canada and Mexico. The balloons traveled on high-altitude and high-speed currents over the Pacific Ocean, today known as the

jet stream Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds (flowing west to east). ...

, and used a sophisticated

ballast Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship ...

system to control altitude on their three-day flight. Despite high hopes for the operation, the bombs were largely ineffective due to damp conditions and malfunctions, causing only minor damage and six deaths (from a single civilian incident in Oregon in May 1945). The Fu-Go balloon bomb was the first weapon to possess intercontinental range, with its flights being the longest-ranged attacks in the history of warfare at the time.

Background

The balloon bomb concept was a brainchild of the

Imperial Japanese Army The was the official ground-based armed force of the Empire of Japan from 1868 to 1945. It was controlled by the Imperial Japanese Army General Staff Office and the Ministry of the Army, both of which were nominally subordinate to the Emperor o ...

's Number Nine Research Laboratory, also known as the Noborito Laboratory, founded in 1927. In 1933, Lieutenant General Reikichi Tada began an experimental balloon bomb program at Noborito, designated Fu-Go, which proposed a

balloon in diameter equipped with a time fuse and capable of delivering bombs up to . The project was stopped by 1935 and never completed. After the

Doolittle Raid The Doolittle Raid, also known as the Tokyo Raid, was an air raid on 18 April 1942 by the United States on the Japanese capital Tokyo and other places on Honshu during World War II. It was the first American air operation to strike the Japan ...

in April 1942, in which American planes bombed the Japanese mainland, the

Imperial General Headquarters The was part of the Supreme War Council and was established in 1893 to coordinate efforts between the Imperial Japanese Army and Imperial Japanese Navy during wartime. In terms of function, it was approximately equivalent to the United States J ...

directed Noborito to develop a retaliatory bombing capability against the U.S. In summer 1942, Noborito investigated several proposals, including long-range bombers that could make one-way sorties from Japan to cities on the U.S. West Coast, and small bomb-laden

seaplane A seaplane is a powered fixed-wing aircraft capable of takeoff, taking off and water landing, landing (alighting) on water.Gunston, "The Cambridge Aerospace Dictionary", 2009. Seaplanes are usually divided into two categories based on their tec ...

s that could be launched from submarines. On September 9, 1942, the latter was tested in the Lookout Air Raid, in which a

Yokosuka E14Y The Yokosuka E14Y ( Allied reporting name Glen) was an Imperial Japanese Navy reconnaissance seaplane transported aboard and launched from Japanese submarine aircraft carriers such as the during World War II. The Japanese Navy designation was ...

seaplane was launched from a submarine off the Oregon coast. Warrant Officer

Nobuo Fujita (1911 – 30 September 1997) was a Japanese naval aviator and warrant flying officer of the Imperial Japanese Navy who flew a floatplane from the long-range submarine aircraft carrier and conducted the Lookout Air Raids in southern Orego ...

dropped two large incendiary bombs in

Siskiyou National Forest Siskiyou may refer to: *Siskiyou Mountains, a mountain range in northern California and southern Oregon * Siskiyou National Forest, in Oregon and California *Siskiyou County, California *Siskiyou Trail, an old Native American and pioneer trail conne ...

in the hopes of starting a forest fire and safely returned to the submarine; however, response crews spotted the plane and contained the small blazes. The program was cancelled by the Navy. Also in September 1942, Major General Sueki Kusaba, who had served in the original balloon bomb program under Tada, was assigned to Noborito and revived the Fu-Go project with a focus on longer flights. While the Oregon air raid had not achieved its strategic objectives, it had demonstrated the potential of using unmanned balloons at a lower cost and risk to ignite large-scale forest fires.

Development

By March 1943, Kusaba's team developed a prototype capable of flying at for more than 30 hours. The balloons were constructed from five thin layers of ''

washi is traditional Japanese paper. The term is used to describe paper that uses local fiber, processed by hand and made in the traditional manner. ''Washi'' is made using fibers from the inner bark of the gampi tree, the mitsumata shrub (''Ed ...

'', a durable paper derived from the

paper mulberry The paper mulberry (''Broussonetia papyrifera'', syn. ''Morus papyrifera'' L.) is a species of flowering plant in the family Moraceae. It is native to Asia,konnyaku'' (Japanese potato) paste. The Army mobilized thousands of teenage girls at high schools across the country to laminate and glue the sheets together, with final assembly and inflation tests at large indoor arenas including the Nichigeki Music Hall and

Ryōgoku Kokugikan , also known as Ryōgoku Sumo Hall or Kokugikan Arena, is the name bestowed to two different indoor sporting arenas located in Tokyo. The fist ''Ryōgoku Kokugikan'' opened its doors in 1909 and was located on the lands of the Ekōin temple in R ...

sumo hall in Tokyo. The original proposal called for night launches from submarines located off the U.S. coast, a distance the balloons could cover in 10 hours. A timer would release a

at the end of the flight. Two submarines ( ''I-34'' and ''I-35'') were prepared and two hundred balloons were produced by August 1943, but attack missions were postponed due the need for submarines as weapons and food transports. Engineers next investigated the feasibility of balloon launches against the United States from the Japanese mainland, a distance of at least . Engineers sought to make use of strong seasonal air currents discovered flowing from west to east at high altitude and speed over Japan, today known as the

. The currents had been investigated by Japanese scientist

Wasaburo Oishi was a Japanese meteorologist. Born in Tosu, Saga, he is best known for his discovery of the high-altitude air currents now known as the jet stream. He was also an important Esperantist, serving as the second Board President of the from 1930 to 19 ...

in the 1920s; in late 1943, the Army consulted Hidetoshi Arakawa of the Central Meteorological Observatory, who used Oishi's data to extrapolate the air currents across the Pacific Ocean and estimate that a balloon released in winter and that maintained an altitude of could reach the North American continent in 30 to 100 hours. Arakawa further found that the strongest winds blew from November to March at speeds approaching . File:342-FH-3B23426 (18160066205).jpg, Fu-Go carriage, with labeled electrical circuits, fuses, ring, bombs, and ballast File:342-FH-3B23427 (17537483644).jpg, Altitude control device, with central master

aneroid barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

and backups File:342-FH-3B23434 (18160038915).jpg, Top view of carriage assembly, with control device removed File:342-FH-3B23433 (17537463564).jpg, Bottom view of carriage fuses File:342-FH-3B23428 (18160060525).jpg, Reconstructed balloon at the moment a blowout plug is detonated Changing pressure levels in a fixed-volume balloon posed technical challenges. During the day, heat from the sun increased pressure, risking the balloon rising above the air currents or bursting. A relief valve was added to allow gas to escape when the envelope's internal pressure rose above a set level. At night, cool temperatures risked the balloon falling below the currents, an issue that worsened as gas was released. To resolve this, engineers developed a sophisticated

system with 32 sandbags mounted around a cast aluminum wheel, with each sandbag connected to

gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...

blowout plugs. The plugs were connected to three redundant

s calibrated for an altitude between , below which one sandbag was released; the next plug was armed two minutes after the previous plug was blown. A separate altimeter set between controlled the later release of the bombs. A one-hour activating fuse for the altimeters was ignited at launch, allowing the balloon time to ascend above these two thresholds. Tests of the design in August 1944 indicated success, with several balloons releasing

radiosonde A radiosonde is a battery-powered telemetry instrument carried into the atmosphere usually by a weather balloon that measures various atmospheric parameters and transmits them by radio to a ground receiver. Modern radiosondes measure or calculat ...

signals for up to 80 hours (the maximum time allowed by the batteries). A self-destruct system was added; a three-minute fuse triggered by the release of the last bomb would detonate a block of

picric acid Picric acid is an organic compound with the formula (O2N)3C6H2OH. Its IUPAC name is 2,4,6-trinitrophenol (TNP). The name "picric" comes from el, πικρός (''pikros''), meaning "bitter", due to its bitter taste. It is one of the most acidic ...

and destroy the carriage, followed by an 82-minute fuse that would ignite the hydrogen and destroy the envelope. 342-FH-3B23429c (17972344110)

In late 1942, the Imperial General Headquarters had directed the Navy to begin its own balloon bomb program in parallel with the Army project. Lieutenant Commander Kiyoshi Tanaka led a project that developed a rubberized silk balloon, designated the B-Type (in contrast to the Army's A-Type). The silk material was an effort to create a flexible envelope that could withstand pressure changes. The design was tested in August 1944, but the balloons burst immediately after reaching altitude, determined to be the result of faulty rubberized seams. The Navy program was subsequently consolidated under Army control, in part due to the declining availability of rubber as the war continued. The B-Type balloons were later equipped with a version of the A-Type's ballast system and tested on November 2, 1944; one of these balloons, which was not loaded with bombs, became the first to be recovered by Americans after being spotted in the water off

San Pedro, California San Pedro ( ; Spanish: "St. Peter") is a neighborhood within the City of Los Angeles, California. Formerly a separate city, it consolidated with Los Angeles in 1909. The Port of Los Angeles, a major international seaport, is partially located wit ...

, on November 4. The final A-Type design was in diameter and had a volume of of gas at operating altitude. The bombs most commonly carried by the balloons were: * up to four (typically two)

thermite Thermite () is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create brie ...

incendiary bombs consisting of steel tubes long with ignition charges of magnesium,

potassium nitrate Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and nitra ...

and

barium peroxide Barium peroxide is the inorganic compound with the formula Ba O2. This white solid (gray when impure) is one of the most common inorganic peroxides, and it was the first peroxide compound discovered. Being an oxidizer and giving a vivid green c ...

; * one Type 92 high-explosive anti-personnel bomb consisting of

TNT Trinitrotoluene (), more commonly known as TNT, more specifically 2,4,6-trinitrotoluene, and by its preferred IUPAC name 2-methyl-1,3,5-trinitrobenzene, is a chemical compound with the formula C6H2(NO2)3CH3. TNT is occasionally used as a reagen ...

surrounded by 26 steel rings within a steel casing in diameter and long and welded to a tail fin assembly; * or alternatively to the anti-personnel bomb, one Type 97

incendiary bomb using the Type 92 bomb casing and fin assembly, containing of

and three

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

containers of thermite.

Offensive

Fu-Go balloon bomb launch sites and following stations

A balloon launch organization of three battalions was formed. The first battalion included headquarters and three squadrons totaling 1,500 men in

Ibaraki Prefecture is a prefecture of Japan located in the Kantō region of Honshu. Ibaraki Prefecture has a population of 2,871,199 (1 June 2019) and has a geographic area of . Ibaraki Prefecture borders Fukushima Prefecture to the north, Tochigi Prefecture ...

with nine launch stations at Ōtsu. The second battalion of 700 men in three squadrons operated six launch stations at Ichinomiya, Chiba; and the third battalion of 600 men in two squadrons operated six launch stations at Nakoso, Fukushima. The Ōtsu site featured its own hydrogen plant, while the second and third battalions used hydrogen gas manufactured at factories near Tokyo. The combined launching capacity of the sites was about 200 balloons per day, with 15,000 launches planned through March. Each launch pad consisted of anchor screws drilled into the ground and arranged in a circle the same diameter as the balloons. After laying out a deflated envelope, hoses were used to fill the envelope with hydrogen before it was tied down with guide ropes and detached from the anchors. The carriage was attached and the guide ropes were disconnected. Each launch took between thirty minutes and an hour, depending on the presence of surface winds that made releases difficult. The best time to launch was just after the passing of a high-pressure front, and wind conditions were most suitable for several hours prior to the onshore breezes at sunrise. Suitable launch conditions were expected for only about fifty days through the winter period of maximum jet stream velocity. The first balloons were launched at 0500 on November 3, 1944. Some carriages carried

equipment rather than bombs, and were tracked by

direction finding Direction finding (DF), or radio direction finding (RDF), isin accordance with International Telecommunication Union (ITU)defined as radio location that uses the reception of radio waves to determine the direction in which a radio station ...

stations in Ichinomiya, at

Iwanuma, Miyagi 270px, Iwanuma City Hall is a city located in Miyagi Prefecture, Japan. , the city had an estimated population of 43,946 in 18,062 households, and a population density of 730 persons per km². The total area of the city is . Iwanuma is at the co ...

, at

Misawa, Aomori is a city located in Aomori Prefecture, Japan. , the city had an estimated population of 39,093, and a population density of 330 persons per km². The total area of the city is . Misawa is the location of a large military base, Misawa Air Base ...

, and on

Sakhalin Sakhalin ( rus, Сахали́н, r=Sakhalín, p=səxɐˈlʲin; ja, 樺太 ''Karafuto''; zh, c=, p=Kùyèdǎo, s=库页岛, t=庫頁島; Manchu: ᠰᠠᡥᠠᠯᡳᠶᠠᠨ, ''Sahaliyan''; Orok: Бугата на̄, ''Bugata nā''; Nivkh: ...

to estimate the progress of the balloons across the Pacific Ocean. Two weeks after the discovery of the balloon off San Pedro, another was found in the ocean off Kailua, Hawaii, on November 14. More balloons were found in

Thermopolis, Wyoming Thermopolis is the county seat and largest town in Hot Springs County, Wyoming, United States. As of the 2020 U.S. Census, the town population was 2,725. Thermopolis is Greek for "hot city." It is home to numerous natural hot springs, in whic ...

, on December 6 (along with a crater) and in

Kalispell, Montana Kalispell (, Montana Salish: Ql̓ispé, Kutenai language: kqayaqawakⱡuʔnam) is a city in, and the county seat of, Flathead County, Montana, United States. The 2020 census put Kalispell's population at 24,558. In Montana's northwest regio ...

, on December 11, followed by finds in Marshall, Alaska, and

Estacada, Oregon Estacada is a city in Clackamas County, Oregon, United States, about southeast of Portland. The 2020 population is estimated to be 3,700. According to the 2010 census, the population in 2010 was 2,695. It is the 89th largest city in Oregon an ...

, later in the month. National and state agencies were placed on heightened alert, and forest rangers were ordered to report any balloon sightings and finds. On January 4, 1945, the

Office of Censorship The Office of Censorship was an emergency wartime agency set up by the United States federal government on December 19, 1941 to aid in the censorship of all communications coming into and going out of the United States, including its territories ...

requested that newspaper editors and radio broadcasters give no publicity to balloon incidents; this voluntary censorship was highly effective, with the Japanese military only learning of the Wyoming find. The balloons continued to be discovered all over North America, with sightings and partial or full recoveries in

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

, Arizona, California,

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyomi ...

Iowa Iowa () is a U.S. state, state in the Midwestern United States, Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wiscon ...

Kansas Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the w ...

Michigan Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...

(the easternmost finds),

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Colum ...

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...

Nevada Nevada ( ; ) is a state in the Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the 7th-most extensive, ...

North Dakota North Dakota () is a U.S. state in the Upper Midwest, named after the indigenous Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north and by the U.S. states of Minnesota to the east, South ...

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. ...

South Dakota South Dakota (; Sioux: , ) is a U.S. state in the North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota and Dakota Sioux Native American tribes, who comprise a large portion ...

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by b ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

, Washington, and Wyoming; as well as in Canada in

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Terri ...

, British Columbia,

Manitoba , image_map = Manitoba in Canada 2.svg , map_alt = Map showing Manitoba's location in the centre of Southern Canada , Label_map = yes , coordinates = , capital = Winn ...

Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North Dak ...

, and the

Northwest The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each sep ...

and

Yukon Territories Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...

; in northern Mexico; and at sea. On February 17, 1945, a Japanese propaganda broadcast falsely announced great fires and an American public in panic, declaring casualties in the hundreds to thousands. File:342-FH-3B23422 (18161219731).jpg, Balloon found at

Alturas, California Alturas (Spanish for "Heights"; Achumawi: ''Kasalektawi'') is a city and the county seat of Modoc County, California. Located in the Shasta Cascade region of Northern California, the city had a population of 2,715 at the 2020 census. Alturas i ...

, on January 10, 1945, reinflated for tests File:342-FH-3B23424 (18156536642).jpg, Balloon found near Bigelow, Kansas, on February 23, 1945 File:342-FH-3B23423 (17973857089).jpg, Balloon found near

Nixon, Nevada Nixon is a census-designated place (CDP) in Washoe County, Nevada, USA. The population was 374 at the 2010 census. It is part of the Reno– Sparks Metropolitan Statistical Area. It is the seat of tribal government of the Paiute Pyramid Lake ...

, on March 29, 1945 FIle:342-FH-3B23432 (18160047105).jpg, Aerial photograph of a balloon taken from an American plane File:342-FH-3B23437 (18133550866).jpg, Aerial photograph of a balloon taken from an American plane American authorities concluded the greatest danger from the balloons would be wildfires in the coastal forests of the

during dry months. The

Fourth Air Force The Fourth Air Force (4 AF) is a numbered air force of the Air Force Reserve Command (AFRC). It is headquartered at March Air Reserve Base, California. 4 AF directs the activities and supervises the training of more than 30,000 Air Force Reserv ...

Western Defense Command Western Defense Command (WDC) was established on 17 March 1941 as the command formation of the United States Army responsible for coordinating the defense of the Pacific Coast region of the United States during World War II. A second major resp ...

, and Ninth Service Command organized the "Firefly Project" with a number of

Stinson L-5 Sentinel The Stinson L-5 Sentinel is a World War II-era liaison aircraft used by the United States Army Air Forces, U.S. Army Ground Forces, U.S. Marine Corps and the British Royal Air Force. It was produced by the Stinson Division of the Vultee Airc ...

and

Douglas C-47 Skytrain The Douglas C-47 Skytrain or Dakota (RAF, RAAF, RCAF, RNZAF, and SAAF designation) is a military transport aircraft developed from the civilian Douglas DC-3 airliner. It was used extensively by the Allies during World War II and remained ...

aircraft and 2,700 troops, including 200 paratroopers of the 555th Parachute Infantry Battalion, who were stationed at critical points for use in firefighting missions. Through Firefly, the military used the

United States Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...

as a proxy, unifying fire suppression communications among federal and state agencies and modernizing the Forest Service through the influx of military personnel, equipment, and tactics. In the "Lightning Project", health and agricultural officers, veterinarians, and 4-H clubs were instructed to report any strange new diseases in crops or livestock that could be spread by potential

biological warfare Biological warfare, also known as germ warfare, is the use of biological toxins or infectious agents such as bacteria, viruses, insects, and fungi with the intent to kill, harm or incapacitate humans, animals or plants as an act of war. B ...

. Stocks of decontamination chemicals, ultimately unused, were shipped to strategic points in the western states. Japanese fire balloon shotdown gun

Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War I ...

and Navy fighters were scrambled on several occasions to intercept balloons, but they had little success due to inaccurate sighting reports, bad weather, and the very high altitude at which the balloons traveled. Overall, less than 20 of the balloons were shot down. Experiments conducted on recovered balloons to determine their radar reflectivity had little success. In the "Sunset Project" initiated in early April 1945, the Fourth Air Force attempted to detect the radio signals sent by transmitter balloons using sites in coastal Washington; 95 suspected signals were detected, but were of little use due to the relatively low percentage of balloons with transmitters, and observed fading of the signals as they approached the coast. Few American officials believed at first that the balloons could have come directly from Japan. Early U.S. theories speculated that they were launched from German prisoner of war camps or from Japanese-American internment centers. After bombs of Japanese origin were found, it was believed that the balloons were launched from coastal

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

s. Sand from the sandbags was studied by the

Military Geology Unit The Military Geology Unit was a unit in the United States military during World War II. It was established on June 24, 1942, six months after Pearl Harbor.Terman, Maurice, 1998, ''Military Geology Unit of the U.S. Geological Survey during World ...

of the

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific government agency, agency of the Federal government of the United States, United States government. The scientists of the USGS study th ...

, revealing mineral and

diatom A diatom ( Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising se ...

compositions that corresponded to Ichinomiya.

Aerial reconnaissance Aerial reconnaissance is reconnaissance for a military or strategic purpose that is conducted using reconnaissance aircraft. The role of reconnaissance can fulfil a variety of requirements including artillery spotting, the collection of imager ...

later located two nearby

hydrogen production Hydrogen production is the family of industrial methods for generating hydrogen gas. As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas and other light hydrocarbons, partial oxidation of h ...

facilities, which were destroyed by B-29 bombing raids in April 1945.

Results and abandonment

With little evidence of any effect, General Kusaba was ordered to cease operations in April 1945, believing that the mission had been a total fiasco. In total, about 9,300 balloons were launched (approximately 700 in November 1944, 1,200 in December, 2,000 in January 1945, 2,500 in February, 2,500 in March, and 400 in April), of which about 300 were discovered in North America. This was roughly in line with the Japanese estimate that 10 percent of balloons would survive the journey, and the American estimate by the

Office of Scientific Research and Development The Office of Scientific Research and Development (OSRD) was an agency of the United States federal government created to coordinate scientific research for military purposes during World War II. Arrangements were made for its creation during May ...

that 7 percent had done so. The Fu-Go balloon bomb was the first weapon to possess intercontinental range, with its flights being the longest-ranged attacks in the history of warfare at the time. No wildfires were positively identified as being caused by balloon bombs. The most tactically successful attack took place on March 10, 1945, when one of the balloons descended near Toppenish, Washington, and caused a short circuit in power lines supplying the

Manhattan Project The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project ...

's production facility at the Hanford Engineer Works. Backup devices quickly restored power at the site, but it took three days for its

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from n ...

s to be brought to full capacity; plutonium produced in the reactors was later used in

Fat Man "Fat Man" (also known as Mark III) is the codename for the type of nuclear bomb the United States detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second of the only two nuclear weapons ever used in warfare, the firs ...

, the bomb dropped on Nagasaki in August 1945. Many of the balloons recovered in the U.S. had a high number of unexploded blowout plugs, accountable either to a failure of the battery or fuses. The winter and spring launch dates had limited the chances of the incendiary bombs starting forest fires due to the higher levels of precipitation in the Pacific Northwest; forests were generally snow-covered or too damp to catch fire easily. Furthermore, many targeted regions received disproportionately more precipitation in 1945 than in any other year in the decade, with some areas receiving of precipitation more than normal.

Single lethal attack

Mitchell Monument, Bly, Oregon (6149865447)

On May 5, 1945, six civilians were killed near

Bly, Oregon Bly is an unincorporated small town in Klamath County, Oregon, United States. By highway, it is about east of Klamath Falls. , the population was 207. Geography Bly is in southeastern Klamath County, slightly west of Lake County, along O ...

, when they discovered one of the balloon bombs in Fremont National Forest, becoming the only fatalities from enemy action in the continental U.S. during the war. Reverend

Archie Mitchell Archibald Lionel "Archie" Mitchell is a fictional character from the BBC soap opera ''EastEnders'', played by Larry Lamb. He first appeared on 8 July 2008 as a newest member of the Mitchell family—who had first appeared on the soap in 1990� ...

and his pregnant wife Elsie (age 26) drove to

Gearhart Mountain Gearhart Mountain is a high mountain in Lake County and Klamath County, Oregon, in the United States. It is located in the Gearhart Mountain Wilderness of the Fremont–Winema National Forest, northeast of the Sprague River valley and the to ...

that day with five of their Sunday school students for a picnic. While Archie was moving the car, Elsie and the children found the balloon lying on the ground. A large explosion occurred; the four boys (Edward Engen, 13; Jay Gifford, 13; Dick Patzke, 14; and Sherman Shoemaker, 11) were killed instantly, while Joan Patzke (13) and Elsie died several minutes later. A bomb disposal expert guessed that the bomb had been kicked. Military personnel who arrived on the scene saw that the balloon still had snow beneath it while the surrounding area did not. They concluded that the balloon had drifted to the ground several weeks earlier, and had lain there undisturbed until found by the group. The press blackout in the U.S. was lifted on May 22 to ensure that others were warned of the threat. A memorial, the Mitchell Monument, is located at the point of the explosion, northeast of

Klamath Falls Klamath Falls ( ) is a city in and the county seat of Klamath County, Oregon, United States. The city was originally called ''Linkville'' when George Nurse founded the town in 1867. It was named after the Link River, on whose falls the city was ...

in the

Mitchell Recreation Area Mitchell Recreation Area is a small picnic area located in the Fremont-Winema National Forests, Lake County, Oregon, near the unincorporated community of Bly. In it stands the Mitchell Monument, erected in 1950, which marks the only location in ...

. It was listed in the

National Register of Historic Places The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artistic ...

in 2003. Several Japanese civilians have visited the monument to offer their apologies for the deaths that took place here, and cherry trees have been planted around the monument as a symbol of peace.

After World War II

The remains of balloons have continued to be discovered after the war. At least eight were found in the 1940s, three in the 1950s, two in the 1960s, and one in the 1970s. A device with a live bomb was found near

Lumby, British Columbia Lumby is a small community of 1,731 people, located near the edge of the Monashee Mountains. It is mainly a logging, manufacturing and agriculture community. The village is home to a network of trails along the creek beds, known collectively as ...

, in 2014 and detonated by a

Royal Canadian Navy The Royal Canadian Navy (RCN; french: Marine royale canadienne, ''MRC'') is the naval force of Canada. The RCN is one of three environmental commands within the Canadian Armed Forces. As of 2021, the RCN operates 12 frigates, four attack submar ...

ordnance disposal team. Remains of another balloon were found near

McBride, British Columbia McBride is a village in the Robson Valley region of British Columbia, Canada. The village is located southeast of Prince George, British Columbia, and west of Jasper, Alberta. Incorporated in 1932, McBride is located in the Robson Valley surr ...

, in 2019. Many war museums in the U.S. and Canada exhibit Fu-Go fragments, including the

National Air and Space Museum The National Air and Space Museum of the Smithsonian Institution, also called the Air and Space Museum, is a museum in Washington, D.C., in the United States. Established in 1946 as the National Air Museum, it opened its main building on the Na ...

and Canadian War Museum.

Notes

References

Works cited

* *

External links

Report by U.S. Technical Air Intelligence Center, May 1945
* {{DEFAULTSORT:Fu-Go Balloon Bomb Incendiary weapons World War II weapons of Japan Balloons (aeronautics) American Theater of World War II Balloon weaponry Japanese inventions Weapons and ammunition introduced in 1944