On September 23, 1949, President Harry Truman announced that “within recent weeks an atomic explosion occurred in the USSR.” Four months later, on January 31, 1950, he announced that he had directed the Atomic Energy Commission to work “on all forms of atomic weapons, including the so-called hydrogen or super bomb.” The president put this announcement in the lowest possible key—strictly speaking what he said was that he had told the commission “to continue its work.” But the country understood it just as The New York Times put it in a four-column headline the following morning: TRUMAN ORDERS HYDROGEN BOMB BUILT. Any uncertainty about the nature of the president’s decision was completely removed in early March when he issued a further secret order calling for an all-out effort.
During these same months, or quite possibly even earlier, a parallel decision was made in the Soviet Union. Soviet accounts do not tell us exactly when Stalin and his scientists agreed to try to make thermonuclear weapons, but there is no evidence of any hesitation—indeed, what little there is runs the other way: Soviet scientists were aware of the possibility of thermonuclear weapons from their own knowledge, from Klaus Fuchs, and from occasional American public statements. Soviet sources say that the follow-up on the first successful test of August 1949 was rapid. Thus we must recognize that it was not just Harry Truman’s decision that took the world inescapably into the age of thermonuclear explosions. Eight years earlier, when Franklin Roosevelt told Vannevar Bush that he should make the successful construction of an atomic bomb a matter of top priority, he was making a lonely decision spurred by false fear of what Hitler might be—but was not—trying to do. The world’s entry into the thermonuclear age is the consequence of two national decisions, not one.
For obvious reasons only the American decision is open to our close study, but in considering what happened and did not happen in the United States between September 23 and January 31, it is right to bear in mind, as men did at the time, that the American government did not have the luxury of deciding alone.
This double decision is one of the largest and most fateful that man has ever taken. Fission weapons in themselves are terrible enough, but the potential destructiveness of thermonuclear weapons is genuinely different. After the world’s first multimegaton explosion, on November 1, 1952, the sense of terror and awe that followed Hiroshima was renewed and intensified; it was perhaps especially strong among those who had been closest to the earlier enterprise. Here is Winston Churchill in 1955:
There is an immense gulf between the atomic and hydrogen bombs. The atomic bomb with all its terrors did not carry us outside the scope of human control, or manageable events, in thought or action, in peace or war. But…the first comprehensive review of the hydrogen bomb [shows that] the entire foundation of human …