In 1949, the cold war became a nuclear arms race when the Soviets detonated an atomic bomb. United States military and intelligence services knew that the Soviets were developing an atomic bomb but assumed it was years in the future. They were shocked when air-monitoring stations in Alaska detected “positive radioactive evidence of a recent explosion”—a Soviet atomic test that occurred on August 29, 1949. The American public was stunned. In an understatement, a secret report prepared by the Pentagon noted: “The United States has lost its capability of making an effective atomic attack upon the war-making potential of the USSR without danger of retaliation in kind.”
In January 1950, five months after the Soviet Union successfully exploded an atomic bomb, President Harry Truman authorized the development of a thermonuclear “superbomb”—a device 1,000 times more powerful than the atomic bomb dropped on Hiroshima.
A secret study prepared for the president warned that if the Soviets were to develop an H-bomb before the Americans, “the risks of greatly increased Soviet pressure against all the free world, or an attack against the U.S., will be greatly increased.” The United States exploded its first hydrogen bomb in 1952. The Soviets followed in 1953.