er
an area of approximately 1 mile in radius; therefore the selected
targets should contain a densely built-up area of at least this size.

C. The selected targets should have a high military strategic value.

D. The first target should be relatively untouched by previous
bombing, in order that the effect of a single atomic bomb could be
determined.

The weather records showed that for five years there had never been two
successive good visual bombing days over Tokyo, indicating what might
be expected over other targets in the home islands. The worst month of
the year for visual bombing was believed to be June, after which the
weather should improve slightly during July and August and then become
worse again during September. Since good bombing conditions would
occur rarely, the most intense plans and preparations were necessary in
order to secure accurate weather forecasts and to arrange for full
utilization of whatever good weather might occur. It was also very
desirable to start the raids before September.

DESCRIPTION OF THE CITIES BEFORE THE BOMBINGS

Hiroshima

The city of Hiroshima is located on the broad, flat delta of the Ota
River, which has 7 channel outlets dividing the city into six islands
which project into Hiroshima Bay. The city is almost entirely flat and
only slightly above sea level; to the northwest and northeast of the
city some hills rise to 700 feet. A single hill in the eastern part of
the city proper about 1/2 mile long and 221 feet in height interrupted
to some extent the spreading of the blast damage; otherwise the city
was fully exposed to the bomb. Of a city area of over 26 square miles,
only 7 square miles were completely built-up. There was no marked
separation of commercial, industrial, and residential zones. 75% of
the population was concentrated in the densely built-up area in the
center of the city.

Hiroshima was a city of considerable military importance. It contained
the 2nd Army Headquarters, which commanded the defense of all of
southern Japan. The city was a communications center, a storage point,
and an assembly area for troops. To quote a Japanese report, "Probably
more than a thousand times since the beginning of the war did the
Hiroshima citizens see off with cries of 'Banzai' the troops leaving
from the harbor."

The center of the city contained a number of reinforced concrete
buildings as well as lighter structures. Outside the center, the area