WASHINGTON---(INS)---The army and navy departments revealed Saturday that the greatest danger posed by Japanese paper balloons sent over America during the war was that they might have carried deadly germs instead of explosives.
A joint report on the balloon deployment quoted high Japanese army officers as saying that the balloons were devised as a form of retaliation for the Dolittle air attack on Tokyo in April, 1942.
One balloon bearing explosives caused the deaths of six persons in Oregon.
The report, based on information obtained before and after the Japanese surrender, said that the fear of bacteriological warfare by this means developed when the first enemy balloon [without any attached bombs] was found in December, 1944. Nevertheless, the report added, "No evidence was obtained from the recovered paper balloons of any purpose other than the transportation of bombs and incendiaries."
Purposes of the balloons, as considered by investigators, were said to have ranged from the possibility of their use as bacteriological warfare weapons to transports for explosive anti-personnel bombs. Possibilities of their use merely as a prop for Japanese morale and a means of study of wind currents also were considered, according to the report.
A Japanese officer was said to have estimated for U.S. army investigators that only 9 or 10 per cent of a total of 9,000 balloons launched ever reached the United States. A total of 282 balloons and fragments was recovered in the United States, Canada, Alaska, Mexico and the Pacific Ocean area from December, 1944 to February, 1946, according to the report. The department said it was possible more balloons actually did arrive over North America. They said that many of the balloons may have landed in isolated areas.
It was disclosed that the Japanese production goal had been set at 120,000 balloons, but only 9,000 were finished. The entire production cost of the 9,000 balloons was put at only $2,200 at the prewar rate of exchange.
The department revealed that about 10 per cent of the balloons sent toward America were equipped with radio sending apparatus. Radio direction-finding stations on the island of Honshu kept bearings on the balloons in flight, tracking them about 1,200 miles. The report revealed further that the balloons averaged a speed of up to 150 miles per hour. A considerable number of signals transmitted by the balloons were received by stations in the United States.
Large scale launching of the balloons began in November, 1944 and the last balloons were released April 20, 1945. The army and navy said that radio signals were heard as late as August 11, 1945, indicating that the Japanese still were studying meteorological conditions over the Pacific.
Studies conducted by the Japanese were said to have shown that the winter months were most favorable for launching the balloons. However, 3,000 balloons, the most released in any one month, were launched in March, 1945. The army and navy disclosed that two of this number returned to Japan "but fell in snow and caused no damage."
The report pointed out that, according to one Japanese source, the weight of each balloon, when loaded with bombs and incendiaries, was about 50 pounds.
The departments observed that "remarkably" little use was made of the balloon campaign in Japanese propaganda broadcasts. The army and navy offered the explanation that the Japanese expected damage information to become available from America. But this information was denied the Japanese by complete voluntary censorship of press and radio at request of the army and navy through the office of censorship.