On July 16, a day before Terminal began, scientists working for the Manhattan Project had detonated the world’s first atomic explosion in the desert outside Alamogordo, New Mexico: Operation Trinity. Atop a hundred- foot- tall tower, pieces of plutonium (a heavy metal generated from enriched uranium in atomic reactors—themselves new inventions), carefully machined and sculpted into segments of a sphere, were imploded into a dense core, which then began to fission. The heavy nuclei in the centers of the plutonium atoms split apart, releasing enormous amounts of energy. This physical process was discovered only in December 1938; plutonium was first secretly synthesized as recently as the winter of 1940–1941, and now the Americans held a deliverable weapon. The test had gone perfectly, and the Fat Man bomb, and a simpler uranium 235 gun model, code- named Little Boy, were being shipped off to the Pacific to be detonated over specially selected Japanese cities. Perhaps the Soviets were not needed after all.

Soviet Prime Minister Josef Stalin and President Harry S. Truman before the opening of the Potsdam Conference, the day after the Trinity Test, 07/17/1945. Credit: National Archives.

But still, Stalin needed to be told. Officially, he was an ally, although neither party trusted the other, and technically he was not yet an ally in the Pacific war. Many of the American attendees harbored a growing feeling that Roosevelt’s wartime alliance with Stalin either had been a mistake or was about to become one. Perhaps this was one area where the tendency to get too cozy with the Soviets could be checked. The Manhattan Project, begun as an Anglo- American collaboration, had deliberately and explicitly excluded the Soviet Union from the beginning. As far as Truman and Byrnes knew, Stalin remained completely ignorant of their determined efforts to weaponize uranium and plutonium—but he would certainly know once the first city was destroyed in early August, and he would know he had been left in the dark on purpose. Byrnes’s initial impulse was to leave him there.

Secretary of War Henry L. Stimson disagreed. Stimson was an aged and dedicated Roosevelt appointee and onetime secretary of state under Republican President Herbert Hoover. (Stimson remained an adamant Republican under the two Democratic presidents he served.) Byrnes, not wanting the interference, made a point of not inviting him to the Potsdam meeting, but Stimson came anyway, mostly to advise Truman about S- 1 (his code name for the Manhattan Project). The time for stalling Stalin was over. The minutes of the recent meeting of the Anglo- American Combined Policy Committee on July 4, 1945, record that the secretary of war was already convinced that Potsdam was the place to lift the veil for the Soviets, at least a little:

If nothing was said at this meeting about the T.A. [tube alloys = atomic] weapon, its subsequent early use might have a serious effect on the relations of frankness between the three great allies. [Stimson] had therefore advised the President to watch the atmosphere at the [Potsdam] meeting. If mutual frankness on other questions was found to be real and satisfactory, then the President might say that work was being done on the development of atomic fission for war purposes; that good progress had been made; and that an attempt to use a weapon would be made shortly, though it was not certain that it would succeed.

The Interim Committee—a group of civilian and military officials lightly peppered with scientists that Stimson had convened to discuss the wartime and postwar implications of the atomic bomb—had earlier “unanimously agreed that there would be considerable advantage, if suitable opportunity arose, in having the President advise the Russians that we were working on this weapon with every prospect of success and that we expected to use it against Japan.”

At first, Truman was hostile to the idea of informing Stalin, and Winston Churchill was equally resistant. But the news of Trinity changed everything—for them and for Byrnes. Stimson recorded in his diary that Churchill “now not only was not worried about giving the Russians information of the matter but was rather inclined to use it as an argument in our favor in the negotiations.” He continued: “The sentiment . . . 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.”

On July 24 around 7:30 p.m., after a hard day of negotiations on European issues, Truman sauntered over to Stalin during a pause in the discussions, leaving his interpreter behind, and exchanged a few words. We will never know exactly what he said, or exactly what Stalin answered. The exchange would have enormous repercussions, but Truman, Stalin, and the latter’s interpreter, V. N. Pavlov, have left no immediate transcript of what happened. Truman’s interpreter, Charles “Chip” Bohlen, stayed back as his boss made his move:

Explaining that he wanted to be as informal and casual as possible, Truman said during a break in the proceedings that he would stroll over to Stalin and nonchalantly inform him. He instructed me not to accompany him, as I ordinarily did, because he did not want to indicate that there was anything particularly momentous about the development. So it was Pavlov, the Russian interpreter, who translated Truman’s words to Stalin. I did not hear the conversation, although Truman and Byrnes both reported that I was there . . . Across the room, I watched Stalin’s face carefully as the President broke the news. So offhand was Stalin’s response that there was some question in my mind whether the President’s message had got through. I should have known better than to underrate the dictator.

Bohlen was not the only one who thought there might have been a miscommunication. Everyone in the know—Bohlen, Stimson, Byrnes, Churchill—watched the conversation carefully, although not too carefully, for they did not want to tip off Stalin that the exchange was important. As Byrnes recalled in his 1947 memoirs:

He [Truman] said he had told Stalin that, after long experimentation, we had developed a new bomb far more destructive than any other known bomb, and that we planned to use it very soon unless Japan surrendered. Stalin’s only reply was to say that he was glad to hear of the bomb and he hoped we would use it. I was surprised at Stalin’s lack of interest. I concluded that he had not grasped the importance of the discovery. I thought that the following day he would ask for more information about it. He did not. Later I concluded that, because the Russians kept secret their developments in military weapons, they thought it improper to ask about ours.

By 1958, in his second set of memoirs, he had slightly revised his view:

I did not believe Stalin grasped the full import of the President’s statement, and thought that on the next day there would be some inquiry about this “new and powerful weapon,” but I was mistaken. I thought then and even now believe that Stalin did not appreciate the importance of the information that had been given him; but there are others who believe that in the light of later information about the Soviets’ intelligence service in this country, he was already aware of the New Mexico test, and that this accounted for his apparent indifference.

The Soviet dictator did not leave his own account of the exchange, but some in his delegation did. It is hard to take Soviet Foreign Minister V. M. Molotov’s memoirs as completely reliable, for he recalled something that no one else in the room managed to observe—his own presence at the conversation—yet it seems certain that Stalin informed him about it immediately after. Here is Molotov’s account: “Truman took Stalin and me aside with a secretive look and told us they had a special weapon that had never existed before, a very extraordinary weapon . . . It’s hard to say what he himself thought, but it seemed to me he wanted to shock us. Stalin reacted very calmly, so Truman thought he didn’t understand. Truman didn’t say ‘an atomic bomb,’ but we got the point at once.” There are three important features about this Soviet version: Truman never specifically mentioned the nuclear character of the weapon; the Soviets knew what was actually behind his words, although they did not reveal it; and Stalin and his entourage saw this as a veiled threat. Marshal Georgii Zhukov, the commander of the Red Army and thus a crucial figure at Potsdam, believed that Truman had gone up to Stalin “obviously with the goal of political blackmail,” but noted that Stalin “didn’t give away any of his feelings, acting as if he found nothing important in H. Truman’s words.”

Which leaves us with the important question: What did Stalin think? What, in fact, did he really know about the atomic bomb before Truman’s comment? Truman was certain that he knew nothing. As he stated in an interview in 1959: “When [New York Times journalist William Laurence] says that Stalin knew, he did not. He knew nothing whatever about it until it happened . . . He knew no more about it than the man in the moon.” Yet, as is now abundantly clear in evidence from the Soviet archives, Truman misjudged his opponent. Stalin knew quite a lot. On August 7, the day after the destruction of Hiroshima by the Little Boy uranium bomb, Molotov (now back in Moscow) met with U.S. Ambassador Averell Harriman. He told the American: “You Americans can keep a secret when you want to.” Harriman observed “something like a smirk” on Molotov’s face, and later noted that “the way he put it convinced me that it was no secret at all . . . The only element of surprise, I suppose, was the fact that the Alamogordo test had been successful. But Stalin, unfortunately, must have known that we were very close to the point of staging our first test explosion.” Harriman’s intuition was correct. Zhukov noted that Stalin took Molotov aside that evening of Truman’s casual conversation and said, “We need to discuss with Kurchatov the acceleration of our work.” Igor Kurchatov was the scientific director of the Soviet atomic bomb project. Stalin not only knew about the bomb, he was building his own; Truman had not only failed to forestall Soviet proliferation, it appears he had accelerated it.

Excerpted from Red Cloud at Dawn: Truman, Stalin, and the End of the Atomic Monopoly by Michael D. Gordin.Excerpted from Red Cloud at Dawn: Truman, Stalin, and the End of the Atomic Monopoly by Michael D. Gordin.

Copyright © 2009 by Michael D. Gordin.

Reprinted by permission of the publisher.

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