A couple of dates for everyone to work with here. The S-1 Project, which was the predecessor to the Manhattan Project, was formally started on December 18, 1941. The project was not called "Manhattan Project until August,1942 and Brg. Gen'l Leslie Groves was not put in charge of the project until Sept 17, 1942. Groves did not ask Oppenheimer to choose a research site until October, 1942 and he did not select the Los Alamos site until November 16, 1942. The link below has all of this as well as other interesting facts. It seems to me that for the Gov't to know over a year in advance that Los Alamos would be that important, and to save the NG for that use, borders on the omnicient, and at the very least, 1000% better than anything the gov't has done lately.