On January 26, 1939, Danish physicist Niels Bohr announced the discoveries of Lise Meitner and her German colleagues to a physics conference at the George Washington University in Washington, DC. After learning about “atomic fission,” using uranium, some attendees immediately set up an experiment to replicate the results at the nearby Carnegie Institution of Washington and elsewhere. The race for the bomb had begun.

The project’s pace quickened with the selection of hard-driving U.S. Army Corps of Engineers General Leslie R. Groves to direct the project in September 1942. Groves had been in charge of all domestic Army construction needed to mobilize for the war, including the mammoth Pentagon building.

Groves was supremely self-confident, extraordinarily decisive and insightful. He was also an astute judge of people. Despite J. Robert Oppenheimer’s past communist associations and lack of management experience, Groves recognized that Oppenheimer was critical to the success of the project and chose him as its scientific director.

Enrico Fermi, Leo Szilard and other top physicists joined the Manhattan Project effort at the Metallurgical Laboratory or “Met Lab” housed at the University of Chicago. Under the bleachers of Stagg Field, a university stadium, the world’s first controlled, self-sustaining nuclear chain reaction took place in a squash court on December 2, 1942.

The Manhattan Project began as a small research program. At the outset, J. Robert Oppenheimer estimated that 100 scientists could do the research, design and testing at Los Alamos. But the endeavor proved to be far more complex, involving not just scientific research but a gargantuan engineering and industrial effort. Mammoth first-of-a-kind factories were built to produce the fissile material at the core of the bombs, enriched uranium and plutonium.