At a cabinet meeting on September 21, 1945, members of the Truman administration had debated what to do with this powerful new weapon. The issue of international control was complicated by another question: Should the secrets of the atomic bomb be given to the Soviet Union? The Soviets were a wartime ally, lost more than twenty million people fighting the Nazis, and now possessed a military stronger than that of any other country except the United States. Canada and Great Britain had been invited to join the Manhattan Project, while the Soviets hadn’t even been informed of its existence. In a memo to President Truman, Henry Stimson, the outgoing secretary of war, worried that excluding the Soviets from the nuclear club would cause “a secret armament race of a rather desperate character.” He proposed a direct approach to the Soviet Union, outside of any international forum, that would share technical information about atomic energy as a first step toward outlawing the atomic bomb. Otherwise, the Soviets were likely to seek nuclear weapons on their own. Stimson thought that a U.S.-Soviet partnership could ensure a lasting peace. “The only way you can make a man trustworthy,” he told the president, “is to trust him.”
Stimson’s proposal was strongly opposed by Secretary of the Navy James Forrestal. “We tried that once with Hitler,” Forrestal said. “There are no returns on appeasement.” The meeting ended with the Cabinet split on whether to share atomic secrets with the Soviet Union. A few weeks later, George F. Kennan, one of the State Department’s Soviet experts, gave his opinion in a telegram from Moscow, where he was posted at the U.S. embassy. “There is nothing — I repeat nothing,” Kennan wrote, “in the history of the Soviet regime which could justify us in assuming that the men who are now in power in Russia, or even those who have chances of assuming power within the foreseeable future, would hesitate for a moment to apply this [atomic] power against us if by doing so they thought that they might materially improve their own power position in the world.” In the absence of formal guarantees or strict controls, it would be “highly dangerous” to give the Soviets any technical information about how to make an atomic bomb. President Truman reached the same conclusion, and the matter was soon dropped.
The United States had good reason to distrust the Soviet Union. In 1939 the Soviet nonaggression pact with Germany was followed by the Nazi invasions of Poland, Belgium, and France. Two years later the Soviet neutrality pact with Japan was followed by the Japanese attack on Pearl Harbor. During the war, the Soviet Union launched its own surprise attacks on Finland, the Baltic states, and Poland — and then executed tens of thousands of their citizens. After encouraging Japanese diplomats to believe it would mediate a peace agreement with the United States, the Soviet Union attacked and occupied Manchuria in the closing days of the war, causing the deaths of perhaps three hundred thousand Japanese soldiers and civilians. The ideology of the Soviet Union sought the overthrow of capitalist governments like that of the United States. And the Soviet leader, Joseph Stalin, was not only paranoid and megalomaniacal, but had already killed almost as many Russians as the Nazis had.
The Soviets had reason to distrust the United States, too. It had intervened militarily in the Russian civil war, using American troops to fight the Red Army until 1920. It had withheld diplomatic recognition of the Soviet Union until 1933. It had suffered vastly fewer casualties fighting the Nazis during the Second World War and yet claimed an equal role in the administration of occupied Germany. The United States government had a long history of opposing almost every form of socialism and communism. Armed with nuclear weapons, it was now the greatest impediment to Soviet influence in Europe, Asia, and the Middle East.