Evidence of about 297 Japanese Balloon Bombs was recovered  throughout the U.S., Canada and Mexico although thousands were reported to have been launched. Most landed in the northwestern part of the continental U.S., Alaska, and British Columbia. However, they were reported as close in as the Aleutian Islands and Hawaii and as far away as Michigan, Texas and Sonora, Mexico. This effort was called Project FUGO by the Japanese and was referred to as Project 32 or The Windship Weapon.
    Only six persons were known to have been killed by such bombs, while many fires were started in the forests of the Northwest. However, little was accomplished from the Japanese point of view in return for the estimated two million dollars required for their construction and launching.
    In preparation for war with the U.S., the Japanese purchased daily weather maps from the U.S. Weather Bureau in 1940. Various sources say the balloon bomb program was initiated in retaliation for the Doolittle raid on Japan proper or the reverses at Midway in 1942.
    There were two types of balloons used against the U.S.: An Army type and a Navy Type.
    The Navy Type “B” balloon was a nine meter balloon with rubber covered Habuti silk. Three hundred of this type were constructed and delivered. Apparently, only 34 Type “B” balloons were launched against the U.S. and they were only test vehicles without bombs. Eventually, the Navy program was consolidated within the Army’s program under Army control and was later suspended.
    The Army Type “A” balloon bomb was ten meters in size. It weighed 152 pounds and had a volume of 19,000 cubic feet. It was made of laminated tissue paper from the bark of the Kozo bush similar to sumac or the Matsumata tree. The bark was rendered into paper sheets of five different sizes, which were glued together by colored Kon-nyaku-nori made from a Japanese potato-like root. A lac-quer type chemical was used to waterproof the paper. About 9,000 of these Army Type “A” balloon bombs were constructed, while some 6,000 were actually launched.
    Both the Army and Navy type balloons were filled with hydrogen gas. The balloons had a scalloped cloth belt with grommets, which held the shrouds for the instruments, ballast and, for the Type “A” balloon, a bomb.
    These balloons traveled around 30,000 feet and used the jet stream of up to 300 miles per hour for its propulsion. To maintain the desired altitude, they used gas relief valves and droppable sandbags. They had a two tube radio transmitter that sent a  wavering tone actuated by a multivibrator  for altitude and pressure readings by means of 24 differing signals. It transmitted on two frequencies alternating between each every ten minutes. In some test baloons, different frequency ranges were used after each sandbag was dropped for monitoring purposes.  Up to four Japanese Army HFDF stations were used, in part, to monitor the progress of the baloon bomb transmissions that lasted about 80 hours, which was usually enough time to reach the continental U.S.
    Usually, the bomb was a 33-lb. high explosive anti-personnel type with a point-detonating fuse. Some balloons carried a 26 lb. or smaller incendiary bomb to start fires, possibly when high explosive bombs were not readily available. The Army Type “A” balloons also had small thermite charges to destroy the instruments and a smaller charge of magnesium powder to destroy the balloon itself upon landing.
    After several years of testing, the operational balloon bombs were finally launched beginning on 3 November 1944 and continued until the end of April 1945. They were launched from three sites: Nakoso, Fukushima Prefecture; Otsu, Ibaraki Prefecture; and, Ichinomiya, Chiba Prefecture, all on the East Coast of Honshu, East and Northeast of Tokyo.
    In the latter part of 1944, we became aware of them at Station H in Hawaii and were tasked to track them for a few weeks on a low priority basis. Usually, our search positions flashed these signals in the 12,000 to 15,000 Khz. range to the Pacific HFDF Net in the slow periods of the late afternoon or early evening watches.
    Some West Coast fighter aircraft units were tasked to shoot down these balloon bombs with limited success.
    Press reports from large newspapers and the wire services were suppressed to keep the Japanese from knowing of any successful landings. However, word of mouth “warnings” of strange objects had made the rounds. School principals, peace officers and politicians had been told if such a strange object were found to leave it alone and call the Army or the FBI. Unfortunately, this word of mouth warning did not help the six who were killed on Gearhart Mountain in Lake County, Oregon on May 5, 1945. A minister and his wife took five Sunday school children, one girl and four boys, for a picnic at the park on the mountain. While the minister was parking his car, one of the boys discovered the balloon and apparently set off the bomb killing the minister’s wife and the five children.
    There is a memorial for the persons killed by this balloon bomb known as the Mitchell Monument located in the Fremont National Forest, Oregon.