Droping of first Atom Bomb

During the final stages of World War II in 1945, the United States conducted two atomic bombings against the cities of Hiroshima and Nagasaki in Japan.

Despite six months of intense strategic fire-bombing of 67 Japanese cities, the Japanese government ignored an ultimatum given by the Potsdam Declaration. By executive order of President Harry S. Truman, the U.S. dropped the nuclear weapon "Little Boy" on the city of Hiroshima on Monday, August 6, 1945, followed by the detonation of "Fat Man" overNagasaki on August 9. These two events are the only active deployments of nuclear weapons in war. The target of Hiroshima was a city of considerable military importance, containing Japan's Second Army Headquarters, as well as being a communications center and storage depot.

Within the first two to four months of the bombings, the acute effects killed 90,000–166,000 people in Hiroshima and 60,000–80,000 in Nagasaki, with roughly half of the deaths in each city occurring on the first day. The Hiroshima prefectural health department estimates that, of the people who died on the day of the explosion, 60% died from flash or flame burns, 30% from falling debris and 10% from other causes. During the following months, large numbers died from the effect of burns, radiation sickness, and other injuries, compounded by illness. In a more plausible estimate of the total immediate and short term cause of death, 15–20% died from radiation sickness, 20–30% from flash burns, and 50–60% from other injuries, compounded by illness. In both cities, most of the dead were civilians.

Six days after the detonation over Nagasaki, on August 15, Japan announced its surrender to the Allied Powers, signing the Instrument of Surrender on September 2, officially ending thePacific War and therefore World War II. Germany had signed its Instrument of Surrender on May 7, ending the war in Europe. The bombings led, in part, to post-war Japan adoptingThree Non-Nuclear Principles, forbidding the nation from nuclear armament. The role of the bombings in Japan's surrender and the U.S.'s ethical justification for them, as well as theirstrategical importance, is still debated.

U.S. President Harry Truman, left, back from the Potsdam conference, is shown at his White House desk with Secretary of War Henry L. Stimson in Washington, D.C., Aug. 8, 1945. They discuss the atomic bomb that was dropped on Hiroshima, Japan

A massive column of billowing smoke, thousands of feet high, mushrooms over the city of Nagasaki, Japan, after an atomic bomb was dropped by the United States on Aug. 9, 1945. A B-29 plane delivered the blast killing approximately 70,000 people, with thousands dying later of radiation effects. The attack came three days after the U.S. dropped the world's first atomic bomb on the Japanese city of Hiroshima. The attacks brought about Japan's unconditional surrender, and the war ended when the papers ofsurrender were accepted aboard the U.S. battleship Missouri on Sept. 2, 1945. (AP Photo/U.S.Signal Corps)

Commanding officer and pilot Col. Paul W. Tibbets Jr. waves from the cockpit of his bomber plane at its base in Tinian, on August 6, 1945, shortly before take-off to drop the first atomic bomb over Hiroshima, Japan. The day before Tibbets named the B-29 Superfortress after his mother "Enola Gay." 

Smoke rises 20,000 feet above Hiroshima on Aug. 6, 1945 after the first atomic bomb was dropped during warfare

The B-29 superfortress Enola Gay lands at its Tinian base after its atomic bombing mission over Hiroshima on Aug. 6, 1945. (AP Photo)

In this undated handout picture from the U.S. Air Force, the ground crew of the B-29 "Enola Gay" which bombed Hiroshima, Japan on Aug. 6, 1945 with the "Little Boy" nuclear bomb, stands with pilot Col. Paul W. Tibbets, center, in the Marianas Islands. It was the first use of nuclear weapons in warfare. (AP Photo/U.S. Air Force)

This is a photograph released by the U.S. government in 1960 that shows the Little Boy atom bomb, the type detonated over Hiroshima on Aug. 6, 1945. The bomb was 29 inches in diameter, 126 inches long and weighed 9,700 pounds with a yield equivalent to 20,000 tons of TNT explosive.