engineering developments and tests. Between the fall of 1942 and June
1945, the estimated probabilities of success had risen from about 60% to
above 90%; however, not until July 16, 1945, when the first full-scale test
took place in New Mexico, was it conclusively proven that the theories,
calculations, and engineering were correct and that the bomb would be
successful.


The test in New Mexico was held 6 days after sufficient material had become
available for the first bomb. The Hiroshima bomb was ready awaiting
suitable weather on July 31st, and the Nagasaki bomb was used as soon after
the Hiroshima bomb as it was practicable to operate the second mission.

The work on the actual selection of targets for the atomic bomb was begun
in the spring of 1945. This was done in close cooperation with the
Commanding General, Army Air Forces, and his Headquarters. A number of
experts in various fields assisted in the study. These included
mathematicians, theoretical physicists, experts on the blast effects of
bombs, weather consultants, and various other specialists. Some of the
important considerations were:

A. The range of the aircraft which would carry the bomb.

B. The desirability of visual bombing in order to insure the most
effective use of the bomb.

C. Probable weather conditions in the target areas.

D. Importance of having one primary and two secondary targets for each
mission, so that if weather conditions prohibited bombing the target there