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The Manhattan Project was officially set up
It was set up by General Leslie Groves and physicist J. Robert Oppenheimer. Since President Roosevelt was skeptical of the necessity of the project at first, they were given only $6,000 in funds. -
First successful test of the bomb
The bomb was code named 'Trinity'. It was detonated at 5:30 A.M. The test took place in the Jornada Del Muerto Desert, which was chosen because it was completely empty and far away from civilization, and the lack of wind in the area. Despite this, people any areas that were even a little bit close were made to evacuate in case something went wrong. -
Manhattan Project Scientists warn the President against using it.
Around 70 scientists who helped develop the bomb sent a letter to Truman, warning him against using it. They argued this because they believed it could not be justified unless Japan was aware of the bombs and still refused to surrender. They also warned that this could make the U.S. vulnerable to nuclear attacks in retaliation. -
President Truman warns Japan at the Potsdam conference of what will happen if they do not surrender
Truman told Japan that they will face "prompt and utter destruction" if they do not unconditionally surrender when he and the other Allied leaders met at Potsdam, Germany. Japan still refused to surrender because they didn't agree with the terms that the Allies made, such as democratic elections and forcing their emperor, Hirohito, to step down. -
The first bomb is dropped on Hiroshima
The first bomb, nicknamed 'Little Boy', was dropped. It was the first atomic bomb ever created. It killed over 80,000 Japanese citizens immediately on impact, and even more were killed in the aftermath due to things like radiation poisoning, injuries, and burns. -
President Truman gives a speech in the aftermath of the bombing on Hiroshima.
President Truman made a speech on the day of the bombing explaining why the decision was made. He also warns Japan that more bombs will be dropped if they do not surrender unconditionally. Additionally, he threatens to use the bombs to destroy their ability to participate in the war by targeting their docks and weapon-making factories. The justification he gives for the attack is that the Potsdam Declaration was enough of a warning of what was to come and Japan still did not surrender. -
The second bomb was dropped on Nagasaki
This one was made of plutonium, and was nicknamed 'Fat Man' due to its larger size. It was much more devastating and killed around 100,000 Japanese civilians. -
Japan announces their surrender, ending World War 2
It was officially signed by Emperor Hirohito on September 2. Their surrender unconditional and they accepted the Allies' terms. -
United States Strategic Bombing Survey
President Truman commissioned surveys to test how effective the use of bombs, including the ones for Hiroshima and Nagasaki, was in the war. The surveys determined that the use of the bombs wasn't necessary to get Japan to surrender. The Japanese Supreme War Council already realized that they needed to surrender by May 1945 and no votes were changed to accept the Potsdam Declaration terms. However, the survey does note that Japan surrendered earlier than they would've if the bombs were not used.