19. In the “arm’s race” what was developed?

Initially, only the United States possessed atomic weapons, but in 1949 the Soviet Union exploded an atomic bomb and the arms race began. Both countries continued building more and bigger bombs. In 1952, the United States tested a new and more powerful weapon: the hydrogen bomb.

Explanation:

which time period is this? or is this story fictional, i'm going to need more info to answer this question