Oppenheimer was the director of the Manhattan nuclear weapons program during World War II. In addition to his activities related to atomic weapons, Oppenheimer had great achievements in other fields of physics, including the study of black holes and cosmic rays. He devoted the rest of his life after developing the atomic bomb to activities aimed at limiting the proliferation of nuclear weapons. He was accused by the US government and secret services of having links with the communist movement and spying activities. In the 1950s he was denied access to secret documents. It was only President Kennedy who rehabilitated him politically. Oppenheimer is today recognized as one of the symbols of pacifism and opposition to nuclear proliferation.