The Allies believed that only an invasion of the Japanese home islands would force the Japanese to surrender. Since 1942 the United States had been working on a secret project called the Manhattan Project to develop the Atomic Bomb. The initial impetus for the project was the fear that the Germans would develop an Atomic bomb. The Germans were forced to abandon the product. On July 16, 1945 the first atomic bomb was detonated near Alamogordo, New Mexico.

After the invasion of Okinawa and the high cost of capturing the island convinced AmAmerican planners that the invasion of Japan would cost 1,000,000 casualties. The decision was made that the only way to end the war was to us the atomic bomb. The bombs were transported to the American airbase on Tinian Island by the USS Indianapolis arriving on July 26, 1945.

Hiroshima a city with a population of between 340,000 and 350,000 at the time was selected as the prime target. It had not been bombed and included important military targets.

The plane selected to cary the bomb was the Enola Gay a B-29 commanded by Colonel Paul W Tibbets. The bomb was armed in flight and at 8:09 August 6, 1945 he began his bombing run over the city. At 8:15 at a height of 31,000 Little Boy was released . it took 44 seconds for the bomb to drop to 1,900 feet and detonate.

The radius of destruction caused by the bomb blast was 1 mile. The fires created an additional 4 miles of destruction. It is estimated that 20,000 Japanese soldiers and between 70,000 - 126,000 were killed.

Sixteen hours after the bombing President Truman announced the fact that the US had done the bombing as said : "If they do not now accept our terms, they may expect a rain of ruin from the air, the like of which has never been seen on this earth. Behind this air attack will follow sea and land forces in such numbers and power as they have not yet seen and with the fighting skill of which they are already well aware.”

The Japanese however were not ready to surrender. They demanded that the home islands and Korea not be occupied and not war trials take place as well as that the emperor remains the titular head of the country. Even the announcement of the Soviets that they were declaring war was not enough to convince the Japanese to surrender.

On the morning of August 9th Major Charles Sweeney piloted the B-29 Bockscar with the Fat Boy bomb aboard. It prime target was Kokura, but Kokura was covered by smoke so the plane headed for the secondary target Nagasaki. The target was the industrial part of the city primary the Mitsubishi Steel and Arms Works it was located in the Urakami Valley. The arms works and all other buildings were destroyed. The hills protected the center of the city. Between 39,000 and 80,000 civilians were killed in the bombing.

The Manhattan Project Collaborators Who Objected to the Use of Atomic Weapons