Atomic Bombings of Hiroshima and Nagasaki

Early in the war, fearing that Germany might build an atomic bomb, the United States launched the Manhattan Project, a vast secret program to build a weapon from nuclear fission. Scientists at Los Alamos, New Mexico, directed by J. Robert Oppenheimer, designed the bombs, and on July 16, 1945, the first nuclear device was exploded in the Trinity test in New Mexico. By then Germany had surrendered, but the war with Japan continued.

After the bloody battles of Iwo Jima and Okinawa, U.S. officials expected Japanese forces to fight fiercely for their home islands; some estimated that an invasion could cost half a million American casualties and perhaps millions of Japanese civilians. These estimates were later cited to justify the bombings. President Truman approved its use; his order of July 25 authorized additional bombs as soon as they were ready. Historians continue to debate the many motives behind the decision, and many American officials criticized it.

Hiroshima. Hiroshima, a city of almost 300,000 civilians and an important military center, was the primary target. At about 8:15 a.m. on August 6, the B-29 Enola Gay, piloted by Colonel Paul Tibbets, released “Little Boy,” which exploded 1,900 feet above the city. Within minutes nine of ten people within half a mile of ground zero were dead. Nearly every structure within a mile was destroyed, and roughly half the city’s population was killed or injured.

Nagasaki. On August 9, the B-29 Bock’s Car, commanded by Major Charles Sweeney, found its primary target, Kokura, obscured by smoke and haze and turned to its secondary target, Nagasaki, where “Fat Man” exploded at 11:02 a.m. Though more powerful than the Hiroshima bomb, it caused less damage because of the city’s hilly terrain.

Survivors began to show symptoms of radiation sickness within days; deaths from it peaked three to four weeks after the attacks.

Emperor Hirohito announced Japan’s surrender on August 15, and Japanese delegates formally signed the surrender aboard the battleship USS Missouri on September 2, 1945. Survivors faced long-term health dangers, including increased cancer risk, for the rest of their lives.

The bombings began the nuclear age. The Soviet Union tested its own atomic bomb in 1949, and the two superpowers raced to build ever more powerful weapons during the Cold War.