Henry Stimson (1887-1950) was een Amerikaanse politicus en minister van Oorlog in 1911-1913 en in 1940-1945, en als zodanig nauw betrokken bij het ontwikkelen van de atoombom. Fragmenten uit zijn dagboeken over de jaren 1944 en 1945 staan hier online.
July 22, 1945 Diary Entry
[...] At ten-forty Bundy and I again went to the British headquarters and talked to the Prime Minister [Winston Churchill] and Lord Cherwell for over an hour. Churchill read Groves' report [over de succesvol verlopen test met de atoombom] in full. He told me that he had noticed at the meeting of the Three [Truman, Churchill, and Stalin] yesterday that Truman was evidently much fortified by something that had happened and that he stood up to the Russians in a most emphatic and decisive manner, telling them as to certain demands that they absolutely could not have and that the United States was entirely against them. He said 'Now I know what happened to Truman yesterday. I couldn't understand it. When he got to the meeting after having read this report he was a changed man. He told the Russians just where they got on and off and generally bossed the whole meeting'. Churchill said he now understood how this pepping up had taken place and that he felt the same way. His own attitude confirmed this admission. He now not only was not worried about giving the Russians information of the matter [i.e., telling them the U.S. had the atomic bomb] but was rather inclined to use it as an argument in our favor in the negotiations. The sentiment of the four of us [Stimson, Churchill, Bundy, and Cherwell] was unanimous in thinking that it was advisable to tell the Russians at least that we were working on that subject and intended to use it if and when it was successfully finished. [...]