Natural and social scientists in Poland and Czechoslovakia entered into the post-war situation with visions of democratic education, promises of new methods and a network of scholarly contacts from the inter-war period. Our project concentrates on mathematicians and other related scientists (disciplines as applied mathematics, science of science, astronomy, geology) and on economiststs and sociologists from both countries, and the way their work on politically relevant research resulted in transborder cooperation. Methodology chosen for the project – entanglement research, based on ego-documents and oral history – allows to achieve a more delicate picture of the transborder contacts as could be achieved with traditional historical methodology. Our approach to sources reflects the thesis that Cold War interconnectedness is best studied from the bottom-up perspective, and not starting from the politically “prescribed” channels.