Truman's New Weapon, July 25, 1945

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Today in 1945, President Harry Truman met briefly with Soviet leader Josef Stalin to discuss a new weapon: the atomic bomb. This casual meeting, which took place while the Second World War still raged in the Pacific, was not just an announcement of technological prowess, but a statement by the American President to the leader of the then-largest communist country on earth of America's power in the post-war world.

The two men met during the Potsdam Conference, a meeting held between July 17 and August 2, 1945 in Potsdam, Germany. In addition to Truman and Stalin, British Prime Minister Winston Churchill was also present. Before the end of the conference, Churchill was replaced by Clement Attlee, whose Labor Party had beaten Churchill's Conservative Party in the recent British elections. President Truman presided over the conference's agenda.

At the time the conference began, the war in Europe had been over for nine weeks. In the Pacific, it was another story. Despite the destruction of their navy and the reclamation of most of their earlier advances, the Japanese continued to fight. US planners were putting the finishing touches on Operation Downfall, the planned invasion of the Japanese home islands. The invasion was to take place in two phases. The first phase was called Operation Olympic, the invasion of Kyushu, the southernmost of the home islands. The second phase was called Operation Coronet, planned for March 1, 1946. Coronet would be the amphibious assault on the main island of Honshu at the Tokyo Plain.

While the Royal Navy would contribute part of its Pacific Fleet to the invasion, the rest of the assets involved would be American. This included the entire Marine Corps, the entire US Pacific Fleet and more than 1.5 million soldiers with 3 million in reserve. Covering the invasion would be the 7th, 8th and 10th Air Forces as well as the American Far Eastern Air Force. General Douglas MacArthur's intelligence staff estimated that American casualties could reach one million by the fall of 1946.

With this in mind, Truman was eager to enlist the aid of the Soviets. Unlike the other allied powers, the Soviet Union was not at war with Japan. The Soviets had suffered tremendous casualties in Europe and Stalin was not initially eager to enter another war so quickly after the cessation of the last one. But Truman's argument was convincing, and Stalin agreed to declare war on the Empire of Japan. At this point, Truman had not told Stalin about the atomic bomb, although Stalin had known of its development due to the extensive Soviet spy network in the United States. This may indicate that Truman was not yet decided about using the bomb against Japan, for he knew that Stalin would insist on its use if he knew for certain it was ready for deployment.

So with a promise from the Soviet leader, Truman mentioned to Stalin on July 25 that the United States possessed a "powerful new weapon", but he did not give specifics. According to Truman biographers, Stalin's reaction was courteous but muted. Already, the two men were sizing each other up for their roles in the post-war world. Stalin was wasting no time in installing communist governments in eastern and central Europe, a moved that concerned Winston Churchill, the man who coined the term "Iron Curtain" two years later. But Truman held all the cards with the atomic bomb, a weapon that the Soviets would not have for several more years.

Depending on who you ask, Truman was either a staunch anti-communist or soft on the issue. Either way, his mention of a super weapon was undoubtedly taken as a warning by Stalin. Both men knew that their current allegiance had been formed out of common need and little else. It would not survive long past the end of the war. The die for the Cold War was already being cast.

At the end of the conference, the United States, Great Britain and China issued the Potsdam Declaration, which demanded the complete and unconditional surrender of the Japanese Empire. Anything less would result in "prompt and utter destruction"; the atomic bomb was not mentioned. In the end, it would take the use of two atomic bombs to force Tokyo into surrendering. The Soviets invaded parts of Japanese-controlled China immediately after the conference, making good on Stalin's promise to enter the Pacific War. But as the hot war ended officially less than a month later, a new, much more threatening contest was about to begin.