Origins of interest in nuclear physics when George Gamow came to Gt̲tingen and wrote his alpha radioactivity paper. Assisted Max Born with his treatise on quantum mechanics. Worked with Wolfgang Pauli in Zurich on quantum electrodynamics. Half-year in 1930 in Copenhagen working with Niels Bohr. Arrangement lasted until the war when Rosenfeld was called home. War years in Utrecht, Holland. Lived for the next 11 years (until 1958) in England. Topics discussed include 1931 Rome meeting; the reaction at Copenhagen when Bohr received Ernest Rutherford's letter announcing the discovery of the neutron; Werner Heisenberg's three papers on nuclear structure; a colloquium at Copenhagen on the Enrico Fermi experiments; attendance at the 1934 Kharkov conference; the large-scale exodus of German physicists because of the coming to power of Adolf Hitler; and Bohr's assistance in the emigration of refugees. He shows how physicists themselves recognized the significance of what they were doing, and uses of, for examples, the discovery of the neutron, the compound nucleus, the neutrino idea, the positron, the Hideki Yukawa prediction, and fission. Also prominently mentioned are: Patrick Maynard Stuart Blackett, James Chadwick, John Cockcroft, Otto Robert Frisch, Fritz G. Houtermans, Dmitriy Dmitrevich Ivanenko, Lev Davidovich Landau, Rudolph Leo Bernhard Minkowski, Karl Scheel, Eugene Paul Wigner; Conference on Nuclear Physics (1931 : Rome, Italy), Conference on Theoretical Physics (1934 : London, England), Eidgens̲sische Technische Hochschule Zurich, Institute for Theoretical Physics (Copenhagen), Kharkov Conference (1934 : Kharkov, USSR), Niels Bohr Institutet, and University of Manchester.