In WWII, the Imperial Japanese Navy developed and used a weapon that was launched from the island of Japan, traveled across the Pacific Ocean on the jet stream and successfully reached the continental United States, landing in each of the locations showed by some of the blue dots in the picture.

The weapon was called a ‘Fu-Go’ or fire balloon. When translated literally from the Japanese, means ‘ballon bomb’. Hydrogen balloons were launched with varied loads Including a 33 pound (15 kg) antipersonnel bomb to one with a 26 pound (12 kg) incendiary bomb add four 11 pound (5.9 kg) incendiary devices attached.

It was designed as a cheap weapon intended to drop bombs on American cities, forests and farmlands. The jet stream flew at altitudes above 30,000 feet (9.1 km) and could carry a large balloon across the Pacific Ocean in 3 days, traveling a distance of over 5,000 miles (8,000 km).

Introduced in the fall of 1944, they were at the time the longest range attack ever conducted in the history of warfare. From this date until April 1945, the Japanese launched over 9,300 fire balloons of which 300 were found or observed in the U.S.

The weapons did little destruction but did instill a level of fear in the American public. The fire balloons caused 6 deaths from a single incident and a small amount of damage. The deaths occurred near Bly, Oregon when a pregnant woman and five children elected to touch the balloons, resulting in its explosion.

More Info: en.wikipedia.org