Truman and the Atomic Bomb

When Truman became president on April 12th, 1945, upon the death of President Roosevelt, he did not know about the actual bomb project itself. His first information about what was being done came from Secretary of War Henry L. Stimson on April 25th.

Stimson himself was the 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’s 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 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 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. 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. He told me of this in talks with the president on at least two occasions (May 5th, 1951, and August 6th, 1951). He said the appropriation request did not disclose the nature of the project, so he ordered an investigator for his special committee to look into it. In his memoirs, Truman says that he sent investigators into Tennessee (Oak Ridge) and the state of Washington (Hanford) to discover the enormous constructions and their purpose. Immediately afterward, Secretary Stimson called him, and they got together. Stimson did not tell him what the project was but did tell him it concerned the top secret in the government and that they wanted to go ahead without disclosing any information. On Stimson’s assurances, the president called off his investigation and did not investigate further. (EAA talk, Aug. 6, 1951). He told me (May 5th, 1951) that he knew nothing about the bomb project until Stimson went into it with him on April 25th, 1945, after becoming president.

April 12th, 1945:

After Cabinet met, HST says Stimson remained and told him he wanted Truman “to know about an immense project that was underway – a project looking to develop a new explosive of almost unbelievable destructive power.” HST says it left him puzzled: “It was the first bit of information that had come to me about the atomic bomb, but he gave me no details.” He says it was not until the next day that he was told enough to give him some understanding of the developments underway.

He also tells how “many months before, as part of the Committee to Investigate the National Defense Program, of which he was chairman, he sent investigators into Tennessee and Washington to find out what specific enormous constructions were and their purpose. Stimson then came to see him and said he could not tell Truman what it was, but it was the most significant project in the world’s history and was top secret. As a result, Truman says he called off his investigators.

The next day, Truman writes, James F. Byrnes came to see him and told him a few details – that they were perfecting an explosive great enough to destroy the whole world. (Check Byrnes’s version in his book). He says Leahy was with him at the time and that Leahy predicted the bomb would never go off. Truman also says it was later when Vannevar Bush, head of the Office of Scientific Research and Development, came to the White House and was given a scientist’s version of the atomic bomb.

April 13th, 1945:

President Truman’s appointments were:

  • 10:15 – Secretary of State Settings
  • 11:00 – Gen. George C. Marshall, Admiral King, Admiral Leahy, Secretary of War Stimson, Secretary of Navy Forrestal, General Giles.
  • 12:30 – To the Capitol for lunch
  • 2:30 – James F. Byrnes

The president told me (August 6th, 1951) in a long conversation, much of it about the atomic bomb, that it was, he thought, on April 13th that Byrnes, who had been Director of War Mobilization under Roosevelt but had resigned April 2nd, 1945 and was succeeded by Fred M. Vinson, who had succeeded Byrnes as Head of the Office of Economic Stabilization, and Vinson and told him for the first time something about the project and its purpose. Vinson’s name does not appear on the president’s appointment list for that day.

Byrnes had known of the atomic bomb project for some time but in his book “Speaking Frankly” (Page 257), he said he did not remember just when Roosevelt told him about it. He believes it was the summer of 1943.

Source: collections/bomb/large/index.php