That same year, the communists would finally succeeded in developing, with the help of plans stolen from the U.S. by Soviet spies, their own atomic bomb. But the four- or five-year head start which which the United States experienced was enough to grant security to western Europe. The Soviets could not restart their westward conquest, because NATO had used those years to solidify the security and defense of western Europe.
Commenting on Churchill’s speech in Massachusetts, historian William F. Buckley Jr. writes:
Sir Winston, of course, normally speaks with a robust certitude about everything. It is perhaps not “certain” that our monopoly on the atom bomb served during those years as the controlling deterrent to Soviet expansion. But whatever Churchill's extravagances, he cannot be taken lightly. This time, no doubt, he put his finger on the dominant feature of mid-twentieth century international relations: conceivably a single individual could shift the balance of power by delivering to the Soviet Union technological secrets through the use of which they could overcome their strategic disadvantage and proceed to communize Europe.
Naming Alger Hiss and Klaus Fuchs as example, Buckley notes the dynamic of the atomic age. In a post-1945 environment, one person can smuggle data from the United States to the Soviet Union, and that data can carry significance on a scale previously unimaginable.
The historical effect of technology has been called ‘proliferation’ - the notion that technology makes the actions of one individual more significant. The secrets which Fuchs and Hiss sold to the Soviets were powerful enough that they caused ten of thousands of deaths, and could have caused, in a worst-case scenario, millions.
This is something new in the world. Traitors have played critical parts in the past. But many factors - primarily the indecisiveness of any single weapon - have mitigated the consequences of treason. The great traitors of the past have swung battles, but not wars. The situation is different today. An Alger Hiss, critically situated, can, conceivably, determine the destiny of the West. A Klaus Fuchs can deliver to "the thirteen scheming men" what may well be the key to world conquest.
A few sheets of paper, handed to a Soviet intelligence agent by a State Department employee, prolonged the Cold War by years or even decades. One or two individuals had the ability to create misery for millions around the globe.