Memo for General Arnold
July 24, 1945
MEMORANDUM FOR GENERAL ARNOLD
SUBJECT: Groves Project
1. The following plan and schedule for initial attacks using special bombs
have been worked out:
a. The first bomb (gun type) will be ready to drop
between August 1 and 10 and plans are to drop it the first day of good
weather following readiness.
b. The following targets have been selected:
Hiroshima, Kokura, Niigata and Nagasaki.
(1) Hiroshima (population 350,000) is an "Army" city;
a major POE; has large QM and supply depots; has considerable industry and
several small shipyards.
(2) Nagasaki (population 210,000) is a major shipping
and industrial center of Kyushu.
(3) Kokura (population 178,000) has one of the largest
army arsenals and ordnance works; has the largest railroad shops on Kyushu:
and has large munitions storage to the south.
(4) Niigata (population 150,000) is an important
industrial city, building machine tools, diesel engines, etc., and is a key
port for shipping to the mainland.
c. All four cities are believed to contain large
numbers of key Japanese industrialists and political figures who have sought
refuge from major destroyed cities.
d. The attack is planned to be visual to insure
accuracy and will await favorable weather. The four targets give a very high
probability of one being open even if the Weather varies from that forecast,
as they are considerably separated.
e. The bomb will be carried in a master airplane
accompanied by two other project B-29's with observers and special
f. The three B-29's will take off from North Field
Tinian, and fly via Iwo Jima. The use of fighter escort will be determined
by General Spaatz upon consideration of all operational factors.
g. The master plane will attack the selected target
from [?] feet plus altitudewill immediately upon release of the bomb make a
steep diving turn away from the target to achieve maximum slant range
distance as quickly as possible. Recording planes and fighters if employed
will be kept several miles from the target. The particiating planes are
believed to be safe from the effects of the bomb.
h. The bomb will be detonated by radar proximiter fuze
about 2,000 feet above the ground.
i. Emergency arrangements have been provided at Iwo
Jima for handling the bomb if required.
2. Two tested type bombs are expected to be available
in August, one about the 6th and another the 24th. General Groves expects to
have more information on future availabilities in a few days which will be
furnished you when received.
3. The above has been discussed with Generals Spaatz
and Eaker who concur.
JOHN N. STONE