(Editor's note: On Aug. 6, 1945, U.S. military planes dropped the first atomic bomb used in war on the Japanese city of Hiroshima. This is an article United Press, a forerunner of United Press International, published at the time. UPI republishes it as part of an archives Special Report.)
WASHINGTON, Aug. 6, 1945 (UP) -- The most terrifying engine of destruction ever devised by man -- an atomic bomb carrying the explosive force of more than 20,000 tons of TNT -- was turned loose against Japan Sunday (Monday Japan time) as American airmen opened a "surrender or else" assault on the Japanese homeland.
One of the bombs was dropped on the Japanese city of Hiroshima Sunday (Monday in Japan) and the results are still not known, but military men here said the bomb's potentialities stagger the imagination.
It is the first time known that atomic energy has been harnessed for such purposes outside laboratories.
In making the announcement of the bomb, President Truman plainly intimated the bomb's secret is known only to United States and Great Britain experts and military officials and that the Japanese will not be able to copy it.
There was a faint murmur on the Georgetown University seismograph at 6:22 p.m. Sunday of the same day that the bomb was dropped on Japan but seismologists were reluctant to attribute it to the bombing, saying it was "highly improbable" that the explosion would register halfway around the globe.
The war department said the first atomic test firing immediately vaporized a steel tower from which the weapon was suspended and sent a massive cloud billowing 40,000 feet upward with a "tremendous power" and said "a blinding flash lighted the whole area brighter than the brightest sunlight."
A mountain range three miles from the observation point stood out clearly.
There came a tremendous, sustained roar and a heavy pressure wave knocked down two men outside the control tower 10,000 yards from the explosion.
Immediately thereafter a huge multi-colored surging cloud boiled up at an altitude of more than 40,000 feet. Clouds in its path disappeared. Soon shifting stratosphere winds dispersed the narrow gray mass.
The steel tower from which the bomb was suspended was entirely vaporized. Where the tower stood was a huge, sloping crater.
The scientists were dazed but relieved at the success of the tests and promptly marshaled their forces to estimate the strength of America's new weapon.
The answer to their findings rests in the destruction effected upon Japan.
The bomb was tested the first time at 5:30 a.m. on July 16, 1945, in a remote section of the Alamagordo air base, 120 miles southwest of Albuquerque, N.M.