The Soviet Response

The Soviet Union also pursued the development of a hydrogen bomb. Initial Soviet research was guided by the information provided by Klaus Fuchs. Then Andrei Sakharov suggested a different idea. This design, known as, the "Layer Cake", consisted of alternating layers of hydrogen fuel and uranium. However, this design limited the amount of thermonuclear fuel that could be used and therefore the bomb's explosive force.

On August 12, 1953, the Soviet Union tested its first fusion-based device on a tower in central Siberia. The bomb had a yield of 400 kilotons. Though not nearly as powerful as the American bomb tested nine months earlier, it had one key advantage: It was a usable weapon, small enough to be dropped from an airplane.

The mushroom cloud from the Soviet's first hydrogen bomb
The mushroom cloud from the Soviet's first hydrogen bomb

Shortly after the "BRAVO" test, Sakharov's team had the same idea of using radiation implosion. Work on the "Layer Cake" design was halted. On November 22, 1955, the Soviet Union exploded its first true hydrogen bomb at the Semipalatinsk test site. It had a yield of 1.6 megatons.

This began a series of Soviet hydrogen bomb tests culminating on October 23, 1961, with an explosion of about 58 megatons. Khrushchev boasted, "It could have been bigger, but then it might have broken all the windows in Moscow, 4,000 miles away."