Teller played important roles in the development of the atomic and hydrogen bomb. In 1939 he chauffeured another Hungarian physicist, Leó Szilárd, to a meeting with Albert Einstein. Szilárd persuaded Einstein to write to President Roosevelt about the need to develop an atomic bomb. This letter led to the establishment of US atomic programme.

While working on the Manhattan Project, Teller dreamt up a more powerful bomb - the hydrogen bomb. Although many physicists were not convinced that his design would work, Teller was instrumental in persuading Harry Truman, who had followed Roosevelt as President, to approve the project.

In the essay Teller says that only part of him wanted to build the H-bomb, and that the larger part wanted to continue to do 'pure' science. However, the arrest of his friends in Russia, such as Lev Landau, made him determined to protect the US against Soviet expansion.