The declassification of fusion research in 1958 brought Gottlieb’s work international attention at the Atoms-for-Peace Conference in 1958. He became director of the Princeton Plasma Physics Laboratory in 1961 succeeding Lyman Spitzer, Jr. Fusion research had reached an impasse with its inability to control the high-energy plasma. This impasse was not broken until the 1969 Russian development of the tokamak (doughnut-shaped) electromagnetic plasma container. Despite doubts of other American physicists, Gottlieb seized upon the tokamak concept, even visiting the Institute of Atomic Energy in Moscow in 1969. In 1971, funded by the US Air Force, he traveled throughout western Europe visiting plasma research facilities, and by 1972 had managed to get the $13 million funding to build the Princeton Large Torus. He subsequently obtained the funding for the follow-on Tokamak Fusion Test Reactor (TFTR), but didn’t stay as director to see it finally completed in 1982. He was succeeded as director in 1981 by Harold Furth.