Leo Szilard

Leo Szilard was a physicist whose opposition to using the atomic bomb against Japan brought a strategic and moral challenge to the circle shaping American policy. He warned that the weapon could spur an atomic arms race with the Soviet Union, then tried to put that concern before Harry S. Truman. His efforts reached senior officials but not the President directly: Truman never saw Szilard’s petition, delivered only after he had left for Potsdam.## Background and ConcernSzilard, a Hungarian-born physicist at the University of Chicago, had earlier helped persuade Franklin D. Roosevelt, together with Einstein, to initiate the atomic-bomb project. By the spring of 1945, the question confronting him was no longer how to begin the project but what its completion would mean. In early April, he wrote a long memorandum addressed to Roosevelt arguing that using the bomb against Japan could initiate an atomic arms race with Russia. He questioned whether avoiding that longer-term danger might matter more than the immediate military objective of forcing Japan out of the war. Roosevelt’s death meant that the memorandum was never sent to him; Szilard then sought a way to bring his warning to the new President.## Seeking Access to TrumanSzilard arranged an appointment through Albert Cahn, a mathematician and colleague at the University of Chicago’s Metallurgical Laboratory. Cahn, who came from Kansas City and had once worked for Tom Pendergast to pay his way through graduate school, connected him to Matt Connelly, Truman’s appointments secretary. Connelly had read the memorandum and regarded it as a serious matter, although the appointment’s Kansas City connection initially made him suspicious. He told Szilard that Truman wanted him to see Jimmy Byrnes instead. Szilard did not know that Byrnes served on the Interim Committee or that he was soon to become Secretary of State, and he took an overnight train to Spartanburg with Cahn’s academic colleagues Walter Bartky and Harold Urey.On May 27, only days before the Interim Committee’s final meeting, the three visitors met Byrnes. The memorandum’s claim that only scientists directly involved in the work could assess the situation annoyed him. Szilard himself also made an unfavorable impression on Byrnes, who later described his manner and his wish to participate in policy-making as unwelcome. The meeting therefore exposed a divide not only over policy but over who had standing to shape it: Szilard appealed to the knowledge and responsibility of the scientists, while Byrnes resisted the memorandum’s terms and its author’s intervention.## The Strategic DisputeSzilard’s account of the conversation emphasized the bomb’s possible diplomatic effect. He recalled Byrnes saying that, according to Leslie Groves, Russia had no uranium and that possession of the bomb might make the Russians more manageable. Szilard believed the opposite: the weapon’s possession would intensify, rather than contain, the rivalry. Byrnes later recalled that the visitors’ explanation of the bomb’s power did nothing to ease his own fear of the weapon. The exchange thus left neither side with a simple assurance. The bomb could be imagined as leverage against the Soviet Union, as Szilard warned, or as a terrifying new force whose consequences unsettled even those considering its use.Szilard left Spartanburg determined to prepare a petition opposing the bomb’s use on moral grounds and urging that Japan be warned in advance. On his way back through Washington, he met J. Robert Oppenheimer. Oppenheimer did not share his position; Szilard later recalled that Oppenheimer dismissed the bomb as lacking military significance, despite its capacity to produce an enormous explosion. The disagreement reflected a broader division among scientists over whether a demonstration could end the war, whether direct military use was necessary, and whether using the weapon would damage future efforts to prevent war.## Petition and Absence from the DecisionThe petition Szilard drafted was signed by seventy scientists, but it did not reach Washington until after Truman had departed for Potsdam. Truman never saw it. Nor did he see counter-petitions from scientists who argued that the weapon should be used if it could spare American lives. At the Metallurgical Laboratory in Chicago, a poll of 150 scientists found that 87 percent favored military use if other means failed to bring about surrender. That figure does not erase Szilard’s dissent; it locates it within an unsettled debate in which scientists invoked both morality and the anticipated costs of continued war.The failure of the petition to reach Truman is central to Szilard’s place in this episode. He identified a risk that the immediate military calculation could obscure, pursued access through the new administration, and secured a meeting with a powerful official. But access was not the same as influence over the final decision. The petition arrived too late for the President to consider it, leaving Szilard’s warning about the postwar arms race outside the documents presented to Truman as he weighed the bomb’s use. His intervention therefore records both the presence of scientific dissent and the limits of its reach at the moment of decision.