It has been argued that between 1890 and 1937, urban planning in Central Europe suffered from a “lack of creativity.” The key in designing urban models was the ability of architects to critically evaluate and adapt imported models to local circumstances. The high level of interconnectedness within the profession was decisive: the exchange of knowledge through associations, study travels, congresses, exhibitions, journals and finally, architectural and urban planning competitions. Although the frequency of contacts decreased, these networks survived the ruptures of World War I. Zagreb, undergoing a radical transformation from a provincial administrative center of the Habsburg Empire into the leading economic center of the Kingdom of Serbs, Croats and Slovenes, is an instructive example of the continuity of exchange of urban planning models. In 1930, the city launched an international competition for the Zagreb master plan. It served as a platform for knowledge exchange, but also raised questions about expertise and authority. Who was qualified to sit on those boards and to take decisions? The Zagreb master plan eventually combined German urban practices, in particular the idea of “Siedlung,” with Miljutin’s linear city concept. This result had a formative impact on the development of Croatian urban planning well beyond World War II.