Within two weeks, the 504th Composite Group was ready to fly from Tinian to Japan and deliver its multimillion-dollar payload. From the list of targets that had been preserved for the test, the primary target of Hiroshima was selected. The B-29, "Enola Gay," piloted by the squadron commander, Col. Paul Tibbets, flew to Japan and dropped the bomb on August 6, 1945. The bomb was nicknamed “Little Boy” and used U-238 as its nuclear core.
At 8:15 AM, the line from Hiroshima to Tokyo went dead. Reports started coming in that Hiroshima had been obliterated by air attack. Reports of the dead ranged from 75,000 to 180,000 dead; due to radiation, people would be dying for decades from cancer and birth defects.
Controversy reigns about the use of the Hiroshima bomb. Some have argued that the naval blockade would have starved Japan into submission; others have argued that without the bomb, the millions of casualties expected with the invasion of the home islands would have become a reality. The source for that estimate has never been found.
What is certain is that Japan was preparing the bloodiest reception ever for the Allies if they had invaded Honshu, the southernmost island in Japan. Truman would never have been able to hold office if he had a working weapon and choose not to use it. Also, the Alliance between the Western powers and the Soviets was growing tenuous after the fall of Germany; Truman, an unknown quantity to the Soviets, had to show he was unafraid to use a weapon of mass destruction, especially one that only the United States possessed at that time.
What is not certain is the extent that the Japanese could have responded to the Allied unconditional surrender calls of August 6 and 7, 1945. The damage by conventional bombing to the transportation and communication network prevented the Japanese government from fully understanding what had happened in Hiroshima.
So the government did nothing, and on August 9, 1945, the B-29 "Bock's Car" dropped the “Fat Man” Plutonium bomb on Nagasaki, the tertiary target. This time the bomb was dropped slightly off target, which minimized the effects, the blast stopped by hills near Nagasaki. 70,000 people were killed, but again the aftereffects caused by radiation continued to kill for decades.
On August 15, 1945, the Emperor announced the surrender. The Second World War was over.
In the 1950’s the United States flew several Japanese women to have plastic surgery for their scars caused during the bombing. Ignored in this public relations tour was that thousands of Japanese carried radioactive scars that would be passed on to their children and would trouble them to this day.