Dropping the Atomic Bombs HIROSHIMA AND NAGASAKI JAPAN AUGUST 6 and 9, 1945

What’s Happening in Europe and U.S. April 1945 – FDR dies and Truman takes over the presidency. May 7, 1945 – Germany surrenders. Still have to deal with Japan.

The Decision In Japan, part of the military-dominated Japanese government had begun to realize that a way had to be found to negotiate and end to the war peacefully. However, the Allied demand for “unconditional surrender” was regarded as unacceptable. Under Secretary of State Joseph Grew nonetheless argued that the Japanese might surrender if allowed to retain their Emperor. He also felt that the Emperor would be “the sole stabilizing force” that would make the Japanese armed forces accept a surrender order.

The Decision The few people who knew about the Manhattan Project always assumed that the atomic bomb would be used against Germany or Japan. Many of those people thought it could be used to end the war. Harry S. Truman, who became President after Roosevelt’s death, had no knowledge of the atomic bomb until he was confronted with the decision to use it or not. He saw the atomic bomb principally as a means to end the war quickly and save American lives by not invading Japan.

The Decision Tensions grew between the Soviet Union and the United States, especially in terms of Soviet domination of Poland and other Eastern European countries (Spring 1945). American possession of the atomic bomb might help make the Soviets work cautiously in Europe and elsewhere.

The Decision Some Manhattan Project scientists felt that the bomb project had been a response to a threat from Germany. Attacking Japan without first providing a warning and an opportunity to surrender, would weaken, “our moral position...in the eyes of the world.” They also were concerned that without telling the Soviets first, the use of the bomb would increase the chances of an uncontrolled nuclear arms race. These concerns did not reach Truman.

The Decision The decision to drop the bomb was made in an effort to save American lives. Estimates of the number of American casualties that the planned invasion of Japan would have cost varied widely. One estimate set the number at 31,000. Added to the American losses would be many Japanese casualties, both military and civilian. To prevent an invasion and to save as many lives as possible, Truman chose to use the atomic bomb.

The Bombs Little Boy Hiroshima Weight = 4 tons Energy released: equivalent to 12.5 kilotons of TNT Fat Man Nagasaki Weight = 5 tons Energy released: equivalent to 20 kilotons of TNT

Locations Hiroshima August 6, 1945 Nagasaki August 9, 1945

The Delivery B-29 Bomber named Enola Gay

The Blast Little Boy was detonated 1,900 feet above Hiroshima, Japan. Over 5.4 million degrees Fahrenheit. A fireball formed in 0.1 millisecond, with a temperature of 540,000 degrees Fahrenheit. The top of the atomic cloud reached an altitude of 17,000 meters. Radioactive debris was deposited by "black rain" that fell heavily for over an hour over a wide area.

This bronze Buddha statue was melted by heat from the bomb. Bronze melts at around 1700 degrees F. The temperature on the ground beneath the exploding bomb reached about 7000 degrees.

The Effects HiroshimaNagasaki Before After

The Immediate Effects

Thermal Heat. Intense thermal heat caused severe burns and loss of eyesight. Thermal burns of bare skin occurred over 2 miles from ground zero. Most people exposed to thermal rays within 1 mile radius of ground zero died. Acute symptoms. Symptoms appearing in the first four months were called acute. Besides burns and wounds, they included: general malaise, fatigue, headaches, loss of appetite, nausea, vomiting, diarrhea, fever, abnormally low white blood cell count, bloody discharge, anemia, loss of hair.

The Later Effects Even the people who managed to survive continue for a long time to suffer from aftereffects such as keloid scars, atomic bomb cataract, microcephaly, leukemia and cancer.

Results for the War The bombs effectively forced Japan to surrender. After the war the U.S. occupied Japan and helped it rebuild.