Dissident Soviet physicist Andrei Sakharov, father of the Soviet H-bomb. *

Photo: Corbis * 1953: The Cold War shifts into overdrive with the public acknowledgement by the Soviet Union that it has successfully tested its first hydrogen bomb.

The detonation, which occurred Aug. 12 at the Semipalatinsk test site on the Kazakhstan steppe, allowed the Soviets to draw even in the arms race again. The United States had detonated its first hydrogen bomb the previous November out in the Pacific atolls.

Physicist Andrei Sakharov, who would eventually become one of the USSR's most famous dissidents, was one of the chief designers of its hydrogen bomb. That weapon carried the explosive power of 400 kilotons of TNT, making it roughly 26 times more powerful than the atomic bomb dropped by the Americans on Hiroshima eight years earlier.

Thus began a long rivalry of bomb-test one-upmanship between the world's two superpowers, dragging on through the 1950s into the '60s.

The Soviets, especially, developed a fondness for the hydrogen bomb and tested increasingly powerful versions. The tests culminated in 1961 with the dropping of the so-called Tsar bomb, packing a 60-megaton wallop, making it the most powerful thermonuclear device ever detonated.

There were repercussions far from the testing grounds, too, as both sides became more and more fearful and paranoid of the other. In the United States, within days of the initial Soviet H-bomb announcement, President Eisenhower stripped J. Robert Oppenheimer of his security clearances, believing that the father of the U.S. atomic bomb harbored communist sympathies. Ike also sacked a few thousand government employees who seemed a little too pink for his liking.

(Source: Various)

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