During the Manhattan Project, Teller worked with Enrico Fermi at the University of Chicago to develop the first controlled nuclear chain reaction. Starting in 1943, he headed a group at Los Alamos in the Theoretical Physics division.
While at Los Alamos, Teller became increasingly interested in using nuclear fission to trigger nuclear fusion. However, the complexity of developing a fission bomb post- poned most work on this idea. After the war ended, Teller continued to be a major proponent of the hydrogen (fusion) bomb or “Super”. This position pitted him against Oppenheimer. This issue came to focus during Oppenheimer’s