U.S. drops bomb despite objections
At 5:30 a.m. on July 16, 1945, the United States successfully detonated a new type of bomb with unprecedented destructive capability in the desert near Alamogordo, New Mexico. The United States started its development of atomic bombs in August 1942 in an effort called the Manhattan Project. Albert Einstein, who, along with other physicists in exile, wanted to prevent Nazi Germany from grabbing the lead in the race to build an atomic weapon, wrote a letter to U.S. President Roosevelt calling for greater research in the field. The United States spent more than $2 billion—about $14 billion in today’s dollars—for the project, which was led by Secretary of War Henry Stimson, who was responsible to the President for the project, and General Leslie Groves, the administrator of the project. (See Footnote.)
After the successful test, Brigadier General Thomas Farrell turned to Groves and said, “The war is over.” Groves responded, “Yes, after we drop two bombs on Japan.”
But those who were involved in the test were ordered to keep it strictly to themselves until the bomb was dropped.
The United States and Britain agreed in August 1943 that “the concurrence of Prime Minister Churchill was necessary” before the United States dropped atomic bombs on Japan.
At their meeting in September 1944, Roosevelt and Churchill confirmed that when an atomic bomb was “finally available...after mature consideration, [it should] be used against the Japanese, who should be warned that this bombardment will be repeated until they surrender.”
Assigned to make a decision on the use of the first atomic bomb, the Interim Committee on postwar nuclear policy, led by Stimson, decided that giving warning that an atomic bomb might be dropped could allow Japan to try to shoot down the bomb carrier. Conducting a demonstration to show what carnage might await Japan if it did not lay down its arms would be difficult to arrange. The committee members reached an “agreement that we could not give the Japanese any warning; that we could not concentrate on a civilian area; but that we should seek to make a profound psychological impression on as many inhabitants as possible.”
The agreement was proposed by U.S. Secretary of State James Byrnes and presented to Truman.
At the time, the U.S. government remained of two minds about dropping an atomic bomb on Japan. European Theater of Operations Commanding General Dwight Eisenhower told Stimson he strongly opposed the idea of using the bomb. Eisenhower said later he thought at the time Japan was already on the brink of defeat and “I hated to see our country be the first to use such a weapon.”
Why did the committee adopt a recommendation to use the bomb against Japan?
One of the reasons, Byrnes later said, was that “We did not want to urge the Russians to enter the war.”
After the Yalta Conference, the United States became increasingly suspicious of Moscow’s motives concerning the future of Poland. The United States decided to terminate the war by dropping atomic bombs on Japan and forcing it to surrender before the Soviet Union had the chance to join the fighting.
Washington also wanted to gain the upper hand in the postwar international political arena by intimidating the Kremlin with the use of the atomic bombs against Japan.
The U.S. administration also predicted strong pressure from both houses of the Congress to use the bomb, which was developed at huge expense with tax money, to spare the lives of U.S. soldiers.
Truman asked Harry Hopkins, an adviser to Roosevelt, to visit Moscow to check the situation there. On May 28, Hopkins met Stalin, who told him that the Soviet forces would complete their preparations to join the war by August 8.
The days on which Japan’s fate would be decided—by the eventual entry of the Soviet Union in the war and the dropping of U.S. atomic bombs—were virtually set to come on or around August 8.
Truman refused to include in the Potsdam Proclamation a direct expression suggesting Japan’s Emperor system could be maintained after it surrendered. A scholar’s analysis leads some people to believe that Truman knew Japan would reject a demand for an unconditional surrender that did not guarantee the preservation of the constitutional monarchy.
The directive to drop atomic bombs, written by Groves, was issued on July 25, after approval by General George Marshall, the U.S. Army Chief of Staff. President Truman was not directly involved in the issuance of the directive, but Groves hinted at the President’s tacit consent in his memoirs. According to Groves, Truman’s decision was “basically a decision not to upset existing plans.”
The directive read: “The 509 Composite Group, 20th Air Force, will deliver its first special bomb as soon as weather will permit visual bombing after about 3 August, 1945, on one of the targets: Hiroshima, Kokura, Niigata and Nagasaki.”
Atomic bomb production requires conversion of natural uranium into uranium oxide and then into uranium hexafluoride, from which uranium 235 is extracted to make enriched uranium. The gun barrel-type bomb dropped on Hiroshima was made with uranium 235, which had not been test-detonated beforehand. The world learned of its destructive power for the first time when it was dropped on August 6.
The bomb dropped on Nagasaki three days later was made with plutonium 239. This implosion-type bomb needed the conversion of uranium 238 into plutonium, which is highly fissionable, from which plutonium 239 is chemically extracted. A ball of plutonium 239, wrapped with ordinary detonating powder, is compressed when the powder is ignited and the whole ball is detonated. The pressure triggers nuclear fission. A plutonium bomb was tested in Alamogordo, New Mexico in July 1945.