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 instruments.
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