Why does the notion of freedom of knowledge and teaching in science and engineering matter? What kinds of restrictions have been placed on scientists and engineers, their publications and institutions? Who restrained scientific and engineering knowledge of what sorts; for what reasons; and how successfully? These questions will be addressed by exploring the strategies developed by the U.S. research community to protect the international circulation of knowledge after World War II, when scientific freedom and the export of technical data had to be balanced with the needs of national security. Case studies will include the atomic bomb, the semiconductor industry in the 1970s and space technologies, notably rockets/missiles, in the 1990s. The threat to U.S. economics and military security posed by the Soviet Union in the Cold War, and by China today, has transformed the practice of research in university and in industry alike building new walls around the production and circulation of knowledge to affirm national sovereignty that is, all the while, being undermined by the global circulation of trained scientists and engineers. Not offered 2022-23.