In nineteen thirty-nine, Albert Einstein wrote President Roosevelt a letter. The scientist told the president that it might soon be possible to build a powerful weapon -- a weapon that would use the power of the atom. And he urged Roosevelt to get American scientists to build the atomic bomb before German scientists could build one.

Roosevelt agreed. He created a special team of scientists. Their work became known as the Manhattan Project. Roosevelt made sure that these scientists got all the money and supplies they needed.

Roosevelt died before the scientists could complete their work. But in April nineteen forty-five, the scientists told the new president, Harry Truman, that they were almost ready to test their invention. Just three months later, they exploded the world's first atomic bomb in the desert in the southwestern state of New Mexico.

(SOUND)

Truman had to make a difficult decision. He knew the atomic bomb would cause widespread death and suffering if it was used on a Japanese city. But he was willing to do anything to avoid the need for American troops to invade Japan.

In Japan, a new prime minister and government were searching for a way to end the war. But Truman believed that the Japanese were still not ready to surrender. And he felt it was his duty to end the war as soon as possible.

This undated U.S. Air Force photograph shows the ground crew of the "Enola Gay" airplane that bombed Hiroshima, Japan on August 6, 1945 with the "Little Boy" nuclear bomb