Atomic bombings of Hiroshima and Nagasaki

The United States cooperating with Canada and Great Britain designed and produced first atomic bomb ever within a so called Manhattan Project. The inventor of the bomb Jacob Robert Oppenheimer recommended suitable aims for bombing and on 10 and 11 May 1945 chose the Target Committee five possible targets: Kokura, Hiroshima, Niigata, Yokohama and Kyoto.

On 26 July 1945 the president of United States Truman and other allied leaders issued the Postdam Declaration drafting terms of surrender for Japan. It was the last ultimatum before attacking Japan. Allied leaders announced that the attack would result in „the inevitable and complete destruction of the Japanese armed forces and just as inevitably the utter devastation of the Japanese homeland“. However, the atomic bomb was not mentioned in the ultimatum.

Japanese Government rejected Postdam Declaration and the emperor Hirohito haven‘t done anything to change its opinion. In 1945 it seemed that the use of atomic bomb is the only way how to bring the war to the end early.

Finally was Hiroshima chosen as the target of nuclear bombing mission, the alternative targets were Kokura and Nagasaki. The Bombardment Squadron B-29 Enola Gay, which  name is very well-known, because it was named after the pilot‘s mother, took off from North Field, Tinian, and had to fly for six hours to the target. It would be too dangerous to have armed atomic bomb on the aircraft during taking off, that’s why the safety devices were left in the bomb until the aircraft approached to its destination.

During the night Japanese radar detected a lot of approaching American aircrafts and a raid alert was sounded in Hiroshima. The bomb was dropped from the Enola Gay aircraft at 8:15 in the morning (Japanese time) and it took 44.4 seconds to fall down. The atomic bomb called Little Boy contained about 64 kg of uranium-235. The detonation height was about 580 m above the city. Enola Gay felt down after flying 18.5 km due to the shock waves from the blast. The planned aiming point in Hiroshima was the Aioi Bridge, but the bomb felt because of the strong wind about 240 m further, exactly over Shima Surgical Clinic.

The effect of the bomb was enormous. It created a blast equivalent to 16 kilotons of TNT and the radius of total destruction was about 1.6 km and caused huge fires.

More than 70,000 people, or around 30% of the population of Hiroshima, were killed by the blast and another 70,000 were injured. 69% of buildings in Hiroshima were destroyed.

Americans planned to use the second atomic bomb Fat Man on 11 August 1945, but the bombing was moved earlier by two days, because according to weather forecast bad weather conditions were expected. So the bombing was conducted on 9 August 1945, the primary target was Kokura and the alternative target was Nagasaki. The bomb Fat Man was an implosion-type weapon and was made using plutonium.

The aircraft carrying the bomb, Bockscar, was inspected before the flight. The flight engineer notified that some technical problems appeared. However, due to the lack of time, the problems were not fully recovered.

When Bockscar, accompanied by other aircrafts, approached to Kokura, the target was not clearly visible. There were clouds and black smoke in the air and after three runs over the city, and with fuel running low, they decided to bomb the alternative target – Nagasaki.

At 11:00 in the morning the Fat Man weapon, containing a core of about 6.4 kg of plutonium, was dropped over the city. It exploded about 47 seconds later. Although the Fat Man bomb was more powerful than the one used on Hiroshima, the effect was reduced by hills around the Urakami Valley, where the bomb detonated. From 22,000 to 75,000 people died immediately after the explosion and more people died in the following months due to the consequences of using the nuclear weapon.

The radius of total destruction was about 1.6 km, the blast caused huge fires as well as in Hiroshima. The Mitsubishi Arms Plant and the Mitsubishi Steel Works were significantly damaged. The Nagasaki Arsenal was destroyed in the blast.

After Hiroshima and Nagasaki bombings the Japanese emperor Hirohito decided to capitulate. The surrender was formally signed on 2 September 1945 – on this day the 2nd World War was finally brought to the end.