Balloon Bomb - Smithsonian Institution Libraries

United States Military
Counter/measures
Initial
Detection
The Fourth Air Force, with headquarters at Hamilton
Field, just north of San Francisco, had been charged
with the air defense of the West Coast of the United
States as late as 1943. The threat of air attack had long
before faded and the Fourth Air Force became primarily
involved in training combat replacements. After recovery
of the first few balloons in November and December
1944, the responsibility for a study, along with a defense
against the bombing balloons, was assigned to this
command. This unexpected new menace placed them
once again in the air-defense business.
Instead of the earlier possible threat of massive
assaults by aircraft from Japanese carriers, now the
enemy vehicle was a paper balloon. The seriousness of
this new threat, however, cannot be overemphasized.
This unique Japanese offensive weapon of an unknown
magnitude had tremendous possibilities, and to what
extent these might be developed, the situation was
critical. By mid-December 1944, a military intelligence
project was well underway to evaluate this new weapon
system, but even then there were only a few isolated
incidents from which to draw information.
Aside from the first discovery on 4 November 1944
of a rubberized-silk balloon off the coast of California,
the first report of a balloon incident to reach the Fourth
Air Force was that of a paper balloon discovered on 11
December near Kalispell, Montana. On 19 December the
Western Defense Command reported that a bomb crater
had been discovered near Thermopolis, Wyoming. As an
explosion in that area had been heard during the night of
6 December, it was thought that the crater had been
caused by a balloon-borne bomb on that date. On 31
December, twelve days after the bomb-crater discovery
in Wyoming, a paper balloon and some apparatus were
discovered near Estacada, Oregon.
Local military authorities were puzzled by these
discoveries. When the Kalispell balloon was reported, for
example, it was thought to have been launched from a
Japanese relocation center or from a German prisonerof-war
camp in the United States. Since the first balloon
discovered off San Pedro in early November carried what
was believed to have been radio and meteorological
equipment, local officials concluded that it was perhaps
a weather balloon which had been blown across the
ocean. With the discovery of the Wyoming bomb crater
in December, however, attention was directed toward the
theory that the balloons carried bombs, for the
fragments found near the crater were determined to be
parts of a high-explosive bomb of Japanese manufacture.
During the first two weeks in January 1945, four more
balloons were recovered, and from them additional
information was obtained which led to the conclusion
that the balloons actually were a new, Japanese offensive
weapon.
The War Department was kept fully informed of each
reported balloon incident and, on 4 January 1945, the
Figure 29. Aerial photograph of a Japanese balloon in
flight over Reno, Nevada, taken by a pursuing Bell P-63
King Cobra from Walla Walla Army Air Field, Washington,
on 22 March 1945.
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