When Truman became president on April 12, 1945, upon the death of President Roosevelt, he had no knowledge of the actual bomb project itself and his first information about what was really being done came from Secretary of War Henry L. Stimson on April 25th.
Stimson himself, was virtual head of the project and had been during the years of its development as a military weapon. Stimson had conferred frequently with President Roosevelt during this period but his last meeting with FDR had been on March 15th. (See Stimson biography, "On Active Service." Pg. 615). At that time He discussed a memorandum FDR had sent him from an unnamed "distinguished public servant who was fearful lest the Manhattan (atomic) project "be a lemon"; it was an opinion common among those not fully informed....." The writer, alarmed at rumors of extravagance in the project, suggested they get a body of outside scientists to pass on the peject [project] "because rumors are going around that Vannevar Bush and Jim Conant have sold the President a lemon on the subject and ought to be checked up."
Stimson characterized it as a "jittery and nervous memorandum and rather silly" and he gave the President a list of scientists actually engaged in it.
Truman's first connection with the bomb project - though he knew nothing of what the project was - occurred long before he became President. It was during his senate service as a member of the appropriations committee and as chairman of the Senate Special Committee to Investigate the National Defense Program - known as the "Truman Committee," when the first appropriation for the project came before the appropriations committee. In talks with the President on at least two occasions (May 5, 1951 and August 6, 1951) he told me of this. He...