Atomic arms race

Atomic arms race was the feared consequence that the atomic bomb would not simply end the war but provoke other powers, especially the Soviet Union, to build weapons of their own. The book traces that concern from Leo Szilard’s warning before Hiroshima through the Soviet response to the bomb’s development and the later prediction that future enemies would possess and use similar weapons. It sets the issue against Harry S. Truman’s immediate aim of securing Japan’s surrender and his insistence that decisions about war remain in civilian hands.

The warning before use

In early April 1945, Leo Szilard wrote a memorandum to Franklin D. Roosevelt arguing that using an atomic bomb against Japan could begin an atomic arms race with the Soviet Union. Szilard questioned whether avoiding that outcome might matter more in the long run than the immediate objective of forcing Japan out of the war. Roosevelt’s death meant that the memorandum was not sent to him. Szilard instead sought a meeting with Harry S. Truman, but was directed to James Byrnes, who was then serving on the Interim Committee and would soon become Secretary of State.

At their May 27 meeting, Szilard raised the possibility that possession of the bomb could be used to make the Soviet Union more compliant. As Szilard recounted it, Byrnes thought the weapon might render the Soviets more manageable; Szilard believed it would produce the opposite result. Their disagreement exposed a central strategic divide: the bomb could be imagined as leverage over a rival, but the very effort to use it that way might intensify the rival’s determination to acquire the same capability. Szilard left resolved to petition Harry S. Truman against using the bomb on moral grounds.

The decision and its alternatives

The Interim Committee considered whether the bomb could first be used as a technical demonstration rather than against a city. That option was rejected: the scientists could not propose a demonstration likely to create the shock thought necessary to secure surrender, and there was concern that a weapon that failed after advance notice would strengthen Japanese resistance. General George C. Marshall had earlier considered a military target followed, if needed, by attacks on manufacturing centers with warnings, but the discussion had shifted toward direct military use. The committee’s role was advisory; Henry Stimson emphasized that the responsibility for recommending a course to the President was his alone, while Harry S. Truman later recalled that senior advisers at Potsdam agreed the bomb should be used.

The immediate argument for use was framed around ending the war and avoiding the cost of an invasion. Harry S. Truman later recalled that George C. Marshall estimated an invasion of the Tokyo plain and other parts of Japan could cause at least a quarter of a million American casualties. Truman also described the bomb as a weapon he did not like and said he reached his conclusion only after long, careful thought. The book cautions that there may have been no single moment of decision; by the summer of 1945, the project’s momentum and the demand for Japan’s surrender had made abandoning use difficult to imagine. The debate over alternatives therefore concerned not only how to end the war, but what consequences the chosen means would set in motion.

A rival power already knows

At Potsdam, Harry S. Truman informed Joseph Stalin that the United States had a new weapon of unusual destructive power, without naming it or explaining its scientific basis. Stalin appeared uninterested and did not ask for details. The Americans and British misread that response: Joseph Stalin already knew more than they realized. Soviet nuclear research had begun in 1942, and Klaus Fuchs, a physicist at Los Alamos Laboratory, had been passing atomic information to the Soviet Union. According to the account, Joseph Stalin understood Truman’s announcement and afterward instructed Vyacheslav Molotov to urge the Soviet project forward.

This disclosure turns Szilard’s warning from a future possibility into an unfolding strategic reality. The Soviet Union was not merely a hypothetical recipient of the news that the United States possessed the bomb; it had a research program, access to secrets, and political leadership pressing for faster work. The episode also unsettles the image, later repeated by Harry S. Truman, of a decision followed by a peaceful night’s sleep: the account describes him at Potsdam as sleeping poorly and in greater turmoil than that later recollection suggested.

Consequences and the widening danger

The consequences of the bomb’s use made the future-arms question more immediate. William D. Leahy warned that the destruction at Hiroshima demonstrated frightening lethal possibilities and that other powers would eventually develop the weapon and might use it against the United States. His concern was not limited to the first bomb or to the immediate war; it pointed toward a world in which the capacity to inflict such destruction would spread. The book places that forecast beside the Soviet Union’s already advancing work, giving the warning concrete geopolitical weight.

Harry S. Truman’s response to a letter from Senator Russell also shows the tension between military necessity and limits on the use of force. He wrote that he regretted the prospect of destroying whole populations because of their leaders’ refusal to yield, and said he would not do so unless it was absolutely necessary. He expected that the Soviet Union’s entry into the war might bring Japan to surrender and stressed that, although saving American lives was his objective, he also felt concern for Japanese women and children. In a radio address that night, he urged Japanese civilians to leave industrial cities. These statements do not remove the consequences of the decision, but they show that the prospect of further destruction was not, in his account, an abstract strategic calculation.

The arms-race concept also connects to Harry S. Truman’s broader insistence on civilian control of the war effort. In 1942, he warned that military influence over industry and agriculture could shape the country’s postwar political and economic structure. The atomic decision similarly gathered military advice, scientific disagreement, diplomatic calculation, and presidential responsibility, but left the final judgment with civilian leaders. The resulting tension is central to the concept: controlling the immediate use of the weapon could not by itself control its international consequences, once knowledge and the drive to match an adversary had begun to spread.