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The Atomic Bomb
National Archives 342-FH-A 60593 AC
The atomic blast on August 9, 1945, high above Nagasaki, left little standing.
The Atomic Bomb
(6 and 9 August 1945)
Although there were extensive consultations about the employment of the atomic bomb, discussions always focused on how to use the new weapon, not whether to use it. The primary aim of Allied decision-makers was to achieve the unconditional surrender of Japan as quickly as possible at the lowest cost in lives, and everyone of importance assumed that if the MANHATTAN Project could produce a workable weapon, that weapon would be expended against an enemy target.

It could be argued that the decision to use the atomic bomb was actually made on 6 December 1941, when the first money was approved to fund its development. At the time, American leaders assumed the new invention would be a legitimate weapon in the war, and they never questioned that assumption afterward.

Although President Franklin D. Roosevelt's key advisers on the project concluded in May 1943 that the first operational bomb should be dropped on Japan, the choice of targets really did not receive systematic attention until two years later. A special Target Committee for the MANHATTAN Project began meeting in April 1945, and by the next month it had selected a shortlist of cities including Kyoto and Hiroshima. On 31 May, a blue-ribbon Interim Committee appointed by Secretary of War Henry L. Stimson began meeting to discuss how best to use the new weapon. A suggestion made at lunch to try a warning and noncombat demonstration was quickly rejected for many practical reasons, and the committee recommended that the bomb be dropped without warning on a target that would make the largest possible psychological impression on as many inhabitants as possible.

Eventually, military planners came up with a target list of Hiroshima, Kokura, Kyoto, and Nigata. Stimson persuaded the planners to substitute Nagasaki for the shrine city of Kyoto and then presented the list to President Harry S Truman in late July. Truman approved the directive without consulting anyone else and wrote in his diary that the bomb would be used between 25 July and 10 August. The new weapon offered the possibility of ending the war sooner, and he had no compelling reason not to employ it. Despite some historians' claims to the contrary, there was no reliable evidence of any imminent Japanese collapse or surrender. Although some leaders did perceive a display of the atomic bomb's power as a potential tool to intimidate the Soviet Union in the future, this was a secondary benefit of its employment and not a factor in operational decisions.

No single government document shows Truman's decision to use the bomb, but there were two relevant military directives from the Joint Chiefs to the U.S. Army Air Forces. The first, to General Henry "Hap"? Arnold on 24 July, designated the four possible targets. The next day, a similar order to General Carl Spaatz, who was commanding strategic air forces in the Pacific, added a date: "after about 3 August 1945."? That document also directed that other bombs were to be delivered against targets as soon as they were ready. On the basis of these orders, Spaatz selected Hiroshima and then Kokura to be the targets for the first and second atomic missions. (Cloud cover on the day of the second raid caused the shift to the secondary target of Nagasaki.)

Some critics have questioned why there was not more deliberation about whether to use the terrible new weapon. The main concern for decision-makers was to win the war quickly while avoiding a bloody invasion or losing public support for unconditional surrender. Under the conditions in 1945, which had already produced fire raids that had killed far more Japanese civilians than did the attacks on Hiroshima and Nagasaki, no U.S. president or general could have failed to employ the atomic bomb.

Conrad C. Crane



Bernstein, Barton. "The Dropping of the A-Bomb." Center Magazine (March-April 1983), 7-15.

Kagan, Donald. "Why America Dropped the Bomb." Commentary 100 (September 1995): 17-23.

Merrill, Dennis. The Decision to Drop the Atomic Bomb on Japan. Vol. 1,Documentary History of the Truman Presidency. Bethesda, MD: University Publications of America, 1995.

Wainsrock, Dennis D. The Decision to Drop the Atomic Bomb Westport, CT: Praeger, 1996.

Walker, J. Samuel. Prompt and Utter Destruction: Truman and the Use of Atomic Bombs against Japan. Chapel Hill: University of North Carolina Press, 1997.


Hiroshima, Bombing of

The U.S. bombing of the Japanese city of Hiroshima was the first use of the atomic bomb. On 25 July 1945, commander of United States Strategic Air Forces General Carl Spaatz received orders to use the 509th Composite Group, Twentieth Air Force, to deliver a "special bomb" attack on selected target cities in Japan, specifically Hiroshima, Kokura, Niigata, or Nagasaki. Following rejection of conditions promulgated by the Potsdam Proclamation on 26 July, a declaration threatening Japan with total destruction if unconditional surrender was not accepted, President Harry S Truman authorized use of the special bomb.

Assembled in secrecy and loaded on the Boeing B-29 Superfortress Enola Gay, the bomb consisted of a core of uranium isotope 235 shielded by several hundred pounds of lead, encased in explosives designed to condense the uranium and initiate a fission reaction. Nicknamed "Little Boy," the bomb possessed a force equivalent to 12,500 tons of TNT (12.5 kilotons).

The Enola Gay, commanded by Colonel Paul Tibbets, departed Tinian at 2:45 A.M. on 6 August. Two B-29s assigned as scientific and photographic observers followed, and the three aircraft rendezvoused over Iwo Jima for the run over Japan. Captain William Parsons of the U.S. Navy completed the bomb's arming in the air shortly after 6:30 A.M. The flight to Japan was uneventful, and Tibbets was informed at 7:47 A.M. by weather planes over the targets that Hiroshima was clear for bombing. Japan's eighth largest city (it had about 245,000 residents in August 1945), Hiroshima was an important port on southern Honshu and headquarters of the Japanese Second Army.

The Enola Gay arrived over the city at an altitude of 31,600 feet and dropped the bomb at 8:15:17 a.m. local time. After a descent of some nearly 6 miles, the bomb detonated 43 seconds later some 1,890 feet over a clinic and about 800 feet from the aiming point, Aioi Bridge. The initial fireball expanded to 110 yards in diameter, generating heat in excess of 300,000 degrees Centigrade, with core temperatures over 50 million degrees Centigrade. At the clinic directly beneath the explosion, the temperature was several thousand degrees. The immediate concussion destroyed almost everything within 2 miles of ground zero. The resultant mushroom cloud rose to 50,000 feet and was observed by B-29s more than 360 miles away. After 15 minutes, the atmosphere dropped radioactive "black rain," adding to the death and destruction.

Four square miles of Hiroshima's heart disappeared in seconds, including 62,000 buildings. More than 71,000 Japanese died, another 20,000 were wounded, and 171,000 were left homeless. Some estimates place the number of killed at more than 200,000. About one-third of those killed instantly were soldiers. Most elements of the Japanese Second General Army were at physical training on the grounds of Hiroshima Castle when the bomb exploded. Barely 900 yards from the explosion's epicenter, the castle and its residents were vaporized. Also killed was one American prisoner of war in the exercise area. All died in less than a second. Radiation sickness began the next day and added to the death toll over several years.

Following three observation circuits over Hiroshima, the Enola Gay and its escorts turned for Tinian, touching down at 2:58 p.m. The bombing mission, 12 hours and 13 minutes long covering 2,960 miles, changed the nature of warfare but did not end the war. Truman released a statement on 7 August describing the weapon and calling on Japan to surrender, but his message was ignored by most Japanese leaders as propaganda. The United States dropped another atomic bomb on 9 August, this time on Nagasaki.

Mark E. Van Rhyn



Maddox, Robert James. Weapons for Victory: The Hiroshima Decision Fifty Years Later. Columbia: University of Missouri Press, 1995.

Nobile, Philip. Judgment at the Smithsonian: The Bombing of Hiroshima and Nagasaki. New York: Marlowe and Company, 1995.

Pacific War Research Society. The Day Man Lost: Hiroshima, 6 August 1945. Tokyo: Kodansha International Ltd., 1972.

Thomas, Gordon, and Max Morgan-Witts. Enola Gay. New York: Stein and Day, 1977.


Nagasaki, Bombing Of (9 August 1945)

Second U.S. atomic bombing of a Japanese city. Following the Japanese refusal to surrender following the Hiroshima bombing on 6 August 1945, Twentieth Air Force headquarters on Guam issued Field Order 17 on 8 August, directing that, on the following day, the second atomic bomb on Tinian Island be dropped on another Japanese city. Kokura was designated as the primary target, and Nagasaki, a city of some 230,000 persons, was the alternate.

At 3:49 A.M. on 9 August, Boeing B-29 Superfortress bomber Bockscar (sometimes written as Bock's Car), commanded by Major Charles Sweeney, departed Tinian. It was followed by a second B-29 as scientific observer and a third as photographic observer. The Bockscar carried a plutonium nuclear-fission bomb nicknamed "Fat Man" that was 10 ft 8 inches long and 5 ft in diameter, with a payload greater than that of the Hiroshima bomb. The plutonium 238 isotope core consisted of two melon-shaped hemispheres surrounded by a ring of explosive charges designed to drive the sections together, achieving "critical mass" and a chain reaction releasing 22 kilotons of energy in one-millionth of a second.

Sweeney flew to Kokura but found it overcast and circled for 10 minutes. Despite the clouds, bombardier Kermit Beahan believed they could bomb visually. Sweeney, concerned about a faulty valve that limited fuel, decided to divert to Nagasaki, which was also partly obscured by clouds. Beahan believed he could bomb by radar, but a break in the clouds allowed him to bomb visually, using the Mitsubishi shipyards as his aiming point.

The Bockscar released the bomb from 31,000 ft at 11:02 A.M. local time. The bomb detonated 53 sec later, approximately 1,500 ft over the city, destroying everything within a 1,000 yd radius. An intense blue-white explosion pushed up a pillar of fire 10,000 ft, followed by a mushroom cloud to 60,000 ft.

Although the bomb missed its intended aiming point by 8,500 ft, it leveled one-third of the city. Called the "Red Circle of Death," the fire and blast area within the Urakami Valley section destroyed more than 18,000 homes and killed 74,000 people. Another 75,000 were injured, and many later died from wounds or complications. Blast forces traveling in excess of 9,000 mph damaged buildings 3 mi away, and the concussion was felt 40 mi from the epicenter. "Ashes of Death" from the mushroom cloud spread radiation poisoning, killing all who were not killed outright within 1,000 yd of the epicenter. The bomb might have killed thousands more, but it detonated away from the city center in a heavy industrial area, vaporizing three of Nagasaki's largest war factories but "minimizing" deaths.

Sweeney made one complete circle of the city to determine damage and then left after fuel concerns and heavy smoke made other circuits futile. Critically low on fuel, he flew to Okinawa, landing at Yontan Field about 12:30 P.M., his gas tanks virtually empty. After refueling, Bockscar flew to Tinian, arriving there at 10:30 P.M. local time after a 20-hour flight.

Included in the instrument bundle dropped from the observation plane was a letter addressed to Japanese physicist Professor F. Sagane that urged immediate surrender and threatened continued atomic destruction of Japanese cities. Written by three American physicists, the letter was a bluff, as no other atomic bombs were then ready. Nonetheless, the second atomic attack, coupled with the 8 August declaration of war by the Soviet Union, provided Japanese Emperor Hirohito with the excuse to end the war.

Mark Van Rhyn



Chinnock, Frank W. Nagasaki: The Forgotten Bomb. New York: World Publishing, 1969.

Ishikawa, Eisei. Hiroshima and Nagasaki: The Physical, Medical, and Social Effects of the Atomic Bombings. Trans. David L. Swain. New York: Basic Books, 1981.

Nobile, Philip. Judgment at the Smithsonian: The Bombing of Hiroshima and Nagasaki. New York: Marlowe, 1995.

Toland, John. The Rising Sun: The Decline and Fall of the Japanese Empire, 1936"1945. New York: Random House, 1970.

ABC Clio School

Tucker, Dr. Spencer C.; Roberts, Dr. Priscilla Mary. Encyclopedia of World War II: A Political, Social, and Military History (Santa Barbara, CA: ABC-CLIO. 2005).