Little Boy was the codename for the first atomic bomb to be dropped on the Japanese city of Hiroshima at 08.15 on the 6th of August 1945. The bomb, carried by Enola Gay of the 509th Composate group USAAF, was detonated 1,850 feet above the city centre. 68,000 of Hiroshimas 90,000 buildings were destroyed or damaged beyond repair, of the population of 350,000, it is thought 70,000 were killed and a further 70,000 were seriously injured. Many survivers suffered long term illness and effects from the explosion.
A second bomb, codenamed Fat Man was dropped on Nagasaki 3 days later. Half of the citys buildings were destroyed and 39,000 of the 230,000 people were killed almost instantly.
It was following the second bombing that Japan accepted the Allies demand for unconditional surrender on the 14th of August 1945, effectively ending World War 2.
Little Boy was untested before it was dropped on Hiroshima and simpler in design and operation than Fat Man. Two pieces of Uranium-235 were positioned at opposite ends of the bombs casing. A charge of cordite was placed behind one of them. On command the cordite blasted the Uranium towards the other piece with the velocity of a .45 Calibre bullet. When the two collided the detonation took place, and a temperature of 300,000 degrees celsius was achieved for a fracion of a second. The bomb had a destructive force equalling 20,000 tons of TNT. Fat Man, an implosion weapon using Plutonium-239 instead of Uranium, had been tested in New Mexico on the 16th of July the same year.
Information and pictures taken from the Imperial War Museum, London