Teller continued his research in Germany but when Adolf Hitler came to power in 1933 he decided to move to England. Two years later he emigrated to America and taught at George Washington University before moving to the University of Chicago.
In 1943 Teller joined Robert Oppenheimer, Enrico Fermi, David Bohm, James Franck, James Chadwick, Otto Frisch, Emilio Segre, Eugene Wigner, Felix Bloch, Leo Szilard and Klaus Fuchs on the Manhattan Project. Over the next few years Teller developed the atom bombs dropped on Hiroshima and Nagasaki. He also worked on developing the H-bomb (1946-53).
In 1953 Teller was appointed as professor at the University of California. The following year Teller was a key witness against his colleague, Robert Oppenheimer, who was considered a security risk because he objected to the development of the hydrogen bomb. Unlike Oppenheimer, Teller disagreed with the idea that a scientist should consider the moral implications of research.
The author of Our Nuclear Future (1958), Teller opposed the 1963 test-ban treaty. It was Teller who convinced President Ronald Reagan of the feasibility of the Star Wars Project for militarizing space with fission-bomb-powered X-ray lasers.