Just barely three years out of graduate school, he served as the University of California Livermore Radiation Laboratory's first Director. Since leaving the Lab in 1958, he has held numerous positions in both government and academia, including Chief Scientist of the Advanced Research Projects Agency, Director of Defense Department Research and Engineering, Professor of Physics at the University of California, Berkeley, and Chancellor of the University of California, San Diego. He is currently Director Emeritus of the Institute on Global Conflict and Cooperation at UC San Diego and serves as chairman of the university's Scientific and Academic Advisory Committee, which oversees activities at both Livermore and Los Alamos National Laboratories.