Sergei Kapitsa was a Soviet physicist active after World War II, who became known for speaking out about the possibility of the nuclear winter as a result of nuclear war. He begins by recounting the early history of nuclear physics in Europe and the Soviet Union, noting that the rise of fascism and militarism led to a shutting down of international cooperation. He continues with a description of the Soviet nuclear science community and its reactions to world events and developments in the field during and after the war. Included are personal recollections of the noted scientists Igor Kurchatov and Gyorgy Flerov. He reflects at length on Niels Bohr's travels to the U.S. and England and his thinking on the significance of the bomb. He also touches on Soviet nuclear research as well as on "spymania" in the U.S. at the time.