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EVALUATIONS OF TRINITY (July 1945)
Events
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Dawn of the Atomic Era, 1945
-
The War Enters Its Final Phase, 1945
-
Debate Over How to Use the Bomb, Late Spring
1945
-
The Trinity Test, July 16, 1945
-
Safety and the Trinity Test, July 1945
-
Evaluations of Trinity, July 1945
-
Potsdam and the Final Decision to Bomb, July
1945
-
The Atomic Bombing of Hiroshima, August 6,
1945
-
The Atomic Bombing of Nagasaki, August 9,
1945
-
Japan Surrenders, August 10-15, 1945
-
The Manhattan Project and the Second World War,
1939-1945
Only minutes after the
world's first ever atomic explosion, Leslie Groves and
Robert Oppenheimer (above) began
composing their report for the Secretary of War and
President Truman. There was a sense of
urgency surrounding this notification, as Truman had
already arrived at Potsdam (outside of Berlin) to confer
with other Allied leaders on the conclusion of the war
with Japan. Now that the potential of the bomb had
been proven, the calculations behind the Potsdam
negotiations were dramatically different.
The American contingent to the Big Three conference had
arrived on July 15, 1945, the day before Trinity.
The leader of the Soviet Union, Joseph Stalin, was a day
late, so Truman (left) had additional time to confer with
his Secretary of War, Henry Stimson, and his Secretary of
State, James Byrnes. The key issues to be decided
were the interrelated questions of Soviet participation in
the war against Japan and the wording of an early
surrender offer that might be presented to the
Japanese. This draft surrender document received
considerable attention, the sticking point being the term
"unconditional." It was clear that the Japanese
would fight on rather than accept terms that would
eliminate
the Imperial House or demean the warrior tradition, but
American policy makers feared that anything less than a
more democratic political system and total
demilitarization might lead to Japanese aggression in the
future. Much effort went into finding the precise
formula that would satisfy American war aims in the
Pacific without requiring a costly invasion of the
Japanese mainland. In an attempt to achieve
surrender with honor, the emperor (right) had instructed
his ministers to open negotiations with Russia. The
United States intercepted and decoded messages between
Tokyo and Moscow that made it unmistakably clear that the
Japanese were searching for an alternative to
unconditional surrender.
On July 16, Secretary of War Stimson received a telegram
from his special assistant on atomic issues in Washington,
George L. Harrison. It read:
Operated on this morning. Diagnosis not yet complete
but results seem satisfactory and already exceed
expectations. Local press release necessary as
interest extends great distance. Dr. Groves
pleased. He returns tomorrow. I will keep you
posted.
Stimson immediately informed Truman and Byrnes that the
Trinity test had been successful. The next day
Stimson informed the British Prime Minister, Winston
Churchill, of the test. Churchill expressed great
delight and argued forcefully against informing the Soviet
Union, though he later relented. On July 18, while
debate continued over the wording of the surrender
message, focusing on whether or not to guarantee the place
of the emperor, Stimson received a second cable from
Harrison:
Doctor has just returned most enthusiastic and confident
that the little boy is as husky as his big brother. The
light in his eyes discernible from here to HighhoId and I
could have heard his screams from here to my farm.
Translation: Groves thought the plutonium weapon would be
as powerful as the uranium device and that the Trinity
test could be seen as far away as 250 miles and the noise
heard for fifty miles. Initial measurements taken at
the Alamogordo site suggested a yield in
excess of 5,000 tons of TNT. Truman went back to the
bargaining table with a new card in his hand.
Further information on the Trinity test arrived on July 21
in the form of a long and uncharacteristically excited
report from Groves. Los Alamos scientists now agreed
that the blast had been the equivalent of between 15,000
and 20,000 tons of TNT, higher than generally had been
predicted. Groves reported that glass shattered 125
miles away, that the fireball was
brighter than several suns at midday, and that the steel
tower had been vaporized. Though he had previously
believed it impregnable, Groves stated that he did not now
consider the Pentagon safe from atomic attack.
Stimson informed General George Marshall and then read the
entire report to Truman and Byrnes. Stimson recorded
that Truman was "tremendously pepped up" and that the
document gave him an "entirely new feeling of confidence."
The next day, Stimson, informed that the uranium bomb
would be ready in early August, discussed Groves's report
at great length with Churchill. The British prime
minister was elated and said that he now understood why
Truman had been so forceful with Stalin the previous day,
especially in his opposition to Russian designs on Eastern
Europe and Germany. Churchill then told Truman that
the bomb could lead to Japanese surrender without an
invasion and eliminate the necessity for Russian military
help. He recommended that the President continue to
take a hard line with Stalin. Truman and his
advisors shared Churchill's views. The success
of the Trinity test stiffened Truman's resolve, and he
refused to accede to Stalin's new demands for concessions
in Turkey and the Mediterranean.
On July 24, Stimson met again with Truman. He told
the President that Marshall no longer saw any need for
Soviet help, and he briefed the President on the latest
atomic situation. The uranium bomb might be ready as
early as August 1 and was a certainty by August 10.
The plutonium weapon would be available by August 6.
Stimson continued to favor making some sort of commitment
to the Japanese emperor, though the draft already shown to
the Chinese was silent on this issue. Truman
now had to decide how he would deliver the news of the
atomic bomb to Stalin. Unbeknownst to Truman, the
Soviet leader
already knew.
-
The War Enters Its Final Phase, 1945
-
Debate Over How to Use the Bomb, Late Spring
1945
-
The Trinity Test, July 16, 1945
-
Safety and the Trinity Test, July 1945
-
Evaluations of Trinity, July 1945
-
Potsdam and the Final Decision to Bomb, July
1945
-
The Atomic Bombing of Hiroshima, August 6,
1945
-
The Atomic Bombing of Nagasaki, August 9,
1945
-
Japan Surrenders, August 10-15, 1945
-
The Manhattan Project and the Second World War,
1939-1945
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Sources and notes for this page.
The text for this page was adapted from, and portions
were taken directly from the
Office of History and Heritage Resources
publication:
F. G. Gosling,
The Manhattan Project: Making the Atomic Bomb
(DOE/MA-0001; Washington: History Division, Department
of Energy, January 1999), 49-50. The two cables are quoted in the
History Office publication: Richard G. Hewlett and Oscar
E. Anderson, Jr., The New World, 1939-1946:
Volume I,
A History of the United States
Atomic Energy Commission
(Washington: U.S. Atomic Energy Commission, 1972), 383,
386. Leslie Groves's comment that
he no longer considered the Pentagon safe from attack is
from Leslie R. Groves, Now It Can Be Told (New
York: Harper & Row, 1962), 434. Stimson's
observations on
President Harry Truman's reactions to
the news are from Herbert Feis,
The Atomic Bomb and the End of World War II
(Princeton, NJ: Princeton University Press, 1966),
85. The photograph of Groves with
Robert Oppenheimer is courtesy the
Department of Energy. The photograph of Truman, James Byrnes, and
William Leahy and the photograph of George Harrison,
Groves, James Conant, and
Vannevar Bush are reproduced from
Hewlett and Anderson, The New World, opposite
393 and 417, respectively. Click
here for more information on the photograph of
Trinity. The portrait of Emperor Hirohito is courtesy
the United States Army Signal Corps (via the
Library of Congress). The photograph of George Marshall and Henry
Stimson is courtesy the
Center of Military History, United States Army. The photograph of Joseph Stalin, Truman, and
Winston Churchill at the Potsdam Conference is courtesy
the
Truman Presidential Library.
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