Explore the top-secret American project to build the world's first atomic bomb.

How close was Hitler to launching a nuclear attack against the Allies in World War II? After developing a V2 ballistic missile capable of reaching as far a New York, Hitler made nuclear development his highest priority. On December 3, 1942, the first atomic pile went critical, and maintained a self-contained nuclear chain reaction. This was key in the development of an atomic bomb; however, the Manhattan Project was far from reaching its goals. The Germans had no long range bomber so they moved ahead in ballistic missile development. In May 1943, the A4 missile was successfully demonstrated, making Hitler's highest priority nuclear development. Because nerve agents like tabun and sarin were unreliable, nuclear weapons were the best alternative. Paul Harteck created a low energy nuclear reactor, a major step in Hitler's plans. When the warhead landed, a cloud of dust would arise, spreading death over the area for weeks. If plutonium was put into the warhead, the land would be contaminated for years. However, Hitler's plans failed with the invasion of Normandy, making this the least known close call in modern history.

The United States' decision to use the atomic bomb was made after great debate, but still led to a massive loss of human life.

The K-25 plant in Oak Ridge, Tennessee, was built to enrich uranium for the atomic bomb.