In 1942 General Leslie Groves was chosen to take over Bush's position as the head of the project. During the change they chose to rename the project. The name was changed to the "Manhattan Project." Several laboratories in the United States were used to work on and develop this weapon of mass destruction. Places like the University of Chicago, Oakridge Tennessee, Hanford Washington, and a remote lab in Los Alamos New Mexico all took part. The towns of Hanford and Oakridge were created just to produce the material that would fuel the bomb. For example, by 1945 Oakridge had been transformed from an isolated valley holding a few farms to the fifth largest city in Tennessee. .
By July 1945 the Manhattan Project work was almost completed; they had developed a working nuclear bomb. The only obstacle that stood in their way was the actual testing of the bomb. The test, code name "Trinity," occurred on July 16, 1945 in the New Mexico desert town of Alamogordo. A group of several scientists and high-ranking military officials gathered in a concrete bunker. Finally the first atomic bomb had been detonated and the testing was considered a great success. After receiving a full report of the test, Truman decided dropping the bomb would be the only way to put a quick end to the war. .
Truman was faced with several possible choices when it came to the attack on Japan. Japan posed little or no threat to American forces at this point. The Japanese did however, seem the most driven throughout the war. The battles of Okinawa, Wake, and Guam showed the Japanese were willing to die even in the face of overwhelming odds. .
The kamikaze was a perfect example of this. Japanese pilots would strap themselves into planes loaded with explosives and fly them into American ships. This suicidal type of fighting resulted in tremendous numbers of casualties on both sides. One option available to Truman was a full scale invasion on Kyushu.