The Presidential Timeline

Testing the Bomb

On July 16, 1945, the world’s first atom bomb was exploded at Alamagordo, New Mexico. Code named “Trinity,” the successful test marked the culmination of the three-year Manhattan Project. The top secret project cost more than two billion dollars and employed over 100,000 people.

The test was successful beyond the expectations of many of the project’s scientists. The force of the explosion blasted a crater over twelve feet wide in the earth and was approximately equivalent to fifteen thousand tons of dynamite. The flash of light was so intense witnesses reported it over 200 miles away from the blast site.

President Truman, who had only learned the details of the project in April, received a full report on the successful Trinity test on July 21 while attending the Potsdam Conference. While President Roosevelt had begun the nation’s quest to create an atomic bomb, the final decision to use the bomb fell to Truman.

Using the Atomic Bombs

After consultation with his advisors at Potsdam, Truman decreed that if the Japanese rejected a final surrender ultimatum that was issued on July 26, the bomb would be used against Japan in early August. The first bomb was to be dropped on one of four cities chosen not solely for their strategic importance but also because they had remained relatively unscathed by conventional bombing, which would make the devastating effects of the atomic bomb more evident to the Japanese people.

On August 6 the Enola Gay released the atomic bomb “Little Boy” over Hiroshima, Japan. The bomb leveled the city and left between 70,000 to 100,000 dead. When the Japanese government still refused to surrender, a second bomb, “Fat Man,” was dropped three days later on the city of Nagasaki, killing another 50,000 to 70,000 people. On August 14, the Japanese surrendered, ending World War II.

The Soviet Union and the Bomb

As we learned afterwards, the Russians knew what we were after, and everything about it, down to the complete blueprints.

Robert Nixon Oral History Interview, October 21, 1970

When President Truman mentioned a new weapon of enormous destructive capability to Josef Stalin at the Potsdam Conference, he was puzzled by Stalin’s lack of interest and assumed Stalin had no idea he was speaking of an atomic bomb. Stalin, however, knew a great deal about the atomic weapon from intelligence reports, and only feigned ignorance. He had, in fact, known of the American program almost from its very inception.

Soviet espionage inside the Manhattan Project involved scientists working directly on the Trinity test at Los Alamos. Some historians have estimated that espionage hastened the Soviet acquisition of the atomic bomb by as much as 12-18 months. When the Soviets detonated their first atomic device in August, 1949, it was virtually a replica of the device exploded at Trinity four years earlier.

Strategic Bombing Survey Reports

On August 15, 1945, President Truman requested that the United States Strategic Bombing Survey conduct a study of the effects of the atomic bombs against Japan. The Survey examined confiscated records of the Japanese government and interrogated numerous Government officials and private citizens throughout Japan. The Survey concluded “..that certainly prior to 31 December 1945, and in all probability prior to 1 November 1945, Japan would have surrendered even if the atomic bombs had not been dropped, even if Russia had not entered the war, and even if no invasion had been planned or contemplated.”

Some historians have used these findings to argue against the decision to use the bombs against Japan. Others point out that the Survey had access to information unavailable before the war’s conclusion and that those conducting the survey were champions of conventional bombing and purposefully downplayed the importance of the atomic bombs in securing Japan’s surrender. The debate continues today, confirming President Truman’s decision over 60 years ago as one of the most controversial decisions of the 20th century.

In Truman’s Words

Mr. Truman had discussed at great length the effect of dropping the bomb on bringing the war to a close. That was the one motivating influence. To him, it was going to be instrumental in quickly stopping the war, stopping the destruction and the loss of lives. The loss of lives was particularly plaguing him, because we were having some tremendous losses.

John Snyder Oral History Interview, April 3, 1968

President Truman’s decision to drop the bombs was largely motivated by the war-weary nation’s desire for a quick end to the Pacific War. With the war in Europe over, the nation wanted peace. Advisors had told the President that the cost in human lives of a land invasion in Japan could run into the hundreds of thousands. He had at his disposal the means to save American sailors and soldiers lives and quickly end the war. He made his decision and, as was his nature, defended that decision for the rest of his life.