In 1945, after the German defeat, the American armies in Europe dropped everything and shipped home. Several million Soviet troops remained deployed. Such an imbalance of forces in war-ravaged Europe might have threatened the West as the Cold War opened, but the US monopoly on atomic weapons seemed to counter it. If the West couldn't save Eastern Europe from Soviet domination, its bombs could at least prevent a Soviet march to the Atlantic.

When the Soviet Union tested its first A-bomb in 1949, it upset that balance of forces: It now had both troops on the ground in Europe and atomic weapons. A panicky secret debate began within the US government about how to respond.