The Manhattan Project     The most secret project of all began even before the United States entered the war.  Niels Bohr, a Danish scientist, told American scientists in 1939 that German physicists were close to achieving nuclear fission in the lab.  These scientists knew the potential for building a bomb and, alarmed, they went to Albert Einstein in hopes of getting him to intervene with the President.  Einstein was not yet a household figure, and doubted if he could gain access to the President, so he wrote out the details of the situation, together with his recommendations for action, and gave the letter to Alexander Sachs, a financier and sometime adviser to Roosevelt.  Sachs managed to get through to Roosevelt, who, when he finally understood the portents of the letter, ordered action.  He created the National Defense Research Committee to oversee American experiments with uranium, and also set up an informational exchange with the British, who were working on their own experiments.  Research in atomic power, like most defense research, was farmed out to different universities, and was coordinated through the committee.  Finally, in August 1942, the project was given over to the Army Corps of Engineers to construct research centers.  The Manhattan Engineering District, or the Manhattan Project to develop the atomic bomb, was launched.      But no one, not even the Joint Chiefs, knew about it.  Funding was obtained indirectly, and reports were made directly to Roosevelt.  There were three main installations, in Los Alamos, New Mexico, Oak Ridge, Tennessee, and Hanford, Washington.  The latter two were processing plants where uranium was refined.  But the main project was at Los Alamos, where the scientists were gathered in isolation to work out the design and construction of the bomb itself.  Despite the early intention to share information with the British, the U.S. kept most of its research secret even from its closest ally, until the British threatened to begin their own experiment.  Certainly the Soviets were not informed of what was transpiring in the New Mexico desert.