Family background. Political climate at Columbia University and abroad during undergraduate years beginning 1931; studies at University of Cambridge, effects of political situation on movement of scientists (Petr Kapitsa, Enrico Fermi); graduate work at Columbia with I. I. Rabi, thesis on method for measuring rotational moments, reactions at Columbia to new fission discoveries and verification experiments. English and German atomic energy programs; the MIT Radiation Laboratory, changes due to increased military interest in radar, the National Defense Research Committee (NDRC) security rules, work as expert consultant in Office of Secretary of War Stimson. Head of delivery group under J. Robert Oppenheimer and Leslie Groves at Los Alamos, military and scientific personnel, designs, construction, testing, security arrangements for the atomic bomb; political and moral arguments about use of bomb, military strategies for choosing bomb sites, damage prediction; the Trinity test; Felix Bloch's and Edward Teller's original versions of the H-bomb. Tinian missions, delivery of uranium-235 core, implosion and gun models; reactions to Hiroshima bombing, damage reports by Luis Alvarez and Robert Serber; assembling the plutonium bomb, problems on the second mission, reactions to Russians entering war, U.S. propaganda efforts and events leading up to peace effort. Return to Columbia, postwar conversion of applied laboratories to basic research; Ramsey's research on atomic nuclei and high energy physics; establishment of Brookhaven National Laboratory, appointment of Ramsey as first director of its physics department, peacetime relationship of the military and national laboratories. Move to Harvard University; investigating Communism, 1949, the Veld Committee, the Harvard hearings, the McCarthy hearings investigating Wendell Furry, use of the Fifth Amendment; effects of media coverage, President Pusey's interactions with Joseph McCarthy, Ramsey's appearance on Meet the Press; hearings on General Electric employees; Ramsey's appearances as witness for Martin Kamen and Wendell Furry, outcome of the cases; Oppenheimer hearings, 1954, impact on scientists' motivation for government work; release of secret testimony, AEC reaction to the case. NATO Science Committee, 1958, its inception, organization and accomplishments, Ramsey's role.