Truman approves H-Bomb Development
This bomb was created to cause massive fear for the Soviet Union. It resulted in MAD, massive assured destruction, forcing both countries into a panic. Soon the USSR got the same technology and were prepared for nuclear war.
The US, at the beginning, was on top and dominating. Once the USSR got the bomb as well it made the citizens very scared. The children had to know what to do in-case a bomb is launched during school or at home. Making the US worried for the safety of the future generation.
The USSR felt, as well, that they were scared for their citizens safety, even though they were not as free they still felt the fear. They were prepared to end the war with the bomb. They knew if they fired the US would too, and both "super powers" would be obliterated.
The H-bomb is a huge symbol to the Cold War. The war was based on the fear of being bombed and having nothing to build from. The bomb was what children and families remembered. The bomb was the main threat that both countries had against each other.