The Manhattan Project: Making the Atomic Bomb

Hiroshima

In the early morning hours of August 6, 1945, a B-29 bomber attached to the 590th Composite Group took off from Tinian Island and headed north by northwest toward the Japanese Islands over 1,500 miles away. Its primary target was Hiroshima, an important military and communications center with a population of nearly 300,000 located in the deltas of southwestern Honshu Island facing the Inland Sea. The Enola Gay, piloted by Colonel Paul Tibbets, flew at low altitude on automatic pilot before climbing to 31,000 feet as it neared the target area. As the observation and photography escorts dropped back, the Enola Gay released a 9,700-pound uranium bomb, nicknamed Little Boy, at approximately 8:15 a.m. Hiroshima time. Tibbets immediately dove away to avoid the anticipated shockwaves of the blast. Forty-three seconds later a huge explosion lit the morning sky as Little Boy detonated 1900 feet above the city, directly over a parade field where the Japanese Second Army was doing calisthenics. Though already eleven and a half miles away, the Enola Gay was rocked by the blast. At first Tibbets thought he was taking flak. After a second shockwave hit the plane, the crew looked back at Hiroshima. "The city was hidden by that awful cloud . . .boiling up, mushrooming, terrible and incredibly tall," Tibbets recalled.⁵⁷ Little Boy killed 70,000 people (including about twenty American airmen being held as POWs) and injured another 70,000. By the end of 1945, the Hiroshima death toll rose to 140,000 as radiation sickness deaths mounted. Five years later the total reached 200,000. The bomb caused total devastation for five square miles, with almost all of the buildings in the city either destroyed or damaged.

Within hours of the attack, radio stations began reading a prepared statement from President Harry Truman informing the American public that the United States had dropped an entirely new type of bomb on the Japanese city of Hiroshima-an atomic bomb with more power than 15,000 tons of TNT.⁵⁸ Truman warned that if Japan still refused to surrender unconditionally as demanded by the Potsdam Proclamation of July 26, the United States would attack additional targets with equally devastating results. Two days later, on August 8, the Soviet Union declared war on Japan and attacked Japanese forces in Manchuria, ending American hopes that the war would end before Russian entry into the Pacific theater.

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